METHOD OF USING BIOSURFACTANT-PRODUCING BACTERIA AGAINST FUNGAL AND BACTERIAL PATHOGENS

Abstract

The disclosure provides a method of using a bacterium that is a Bacillus, Streptomyces, Microbacterium, Micrococcus, Rhodococcus, Pseudomonas, Arthrobacter or Staphylococcus and/or a biosurfactant-containing extract isolated from said bacterium, as an antimicrobial agent against a foodborne or a plant bacterial or fungal pathogen, wherein the bacterium optionally comprises at least 3 of bacilysin, difficidin, macrolactin h, bacillaene, bacillomycin d, fengycin, surfactin and bacillibactin. The disclosure also provides a plant or plant part bacterized or coated with a Bacillus or a biosurfactant-containing extract isolated from the Bacillus and a method of protecting a plant or plant part against a bacterial or fungal pathogen comprising bacterizing or coating the plant or plant part with a Bacillus or a biosurfactant-containing extract isolated from the Bacillus, wherein the Bacillus produces or the extract contains at least 3 of bacilysin, difficidin, macrolactin h, bacillaene, bacillomycin d, fengycin, surfactin and bacillibactin.

Claims

1. Method of using a bacterium that is a Bacillus, Streptomyces, Microbacterium, Micrococcus, Rhodococcus, Pseudomonas, Arthrobacter or Staphylococcus and/or a biosurfactant-containing extract isolated from said bacterium, as an antimicrobial agent against at least one foodborne bacterial or fungal pathogen and/or at least one plant bacterial or fungal pathogen.

2. The method of claim 1, wherein the bacterium is (i) a Bacillus, or (ii) a Bacillus velezensis; or a Bacillus amyloliquefaciens.

3. (canceled)

4. The method of claim 1, wherein (a) the bacterium produces, or the biosurfactant-containing extract contains, at least 3 of bacilysin, difficidin, macrolactin H, bacillaene, bacillomycin D, fengycin, surfactin and bacillibactin; and/or (b) the bacterium encodes at least 10 of SEQ ID NOs: 1-111.

5. (canceled)

6. The method of claim 1, wherein the bacterium is a Bacillus velezensis OB9.

7. The method of claim 1, wherein the bacterial or fungal pathogen is (a1) a Salmonella, an Escherichia coli, an Enterobacteriaceae, an Xanthomonas campestris, a Rhizoctonia solani or a Botrytis cinereal; or (a2) a Salmonella or a Xanthomonas campestris.

8. (canceled)

9. The method of claim 1, wherein the at least one bacterial or fungal pathogen comprises at least one foodborne pathogen and at least one plant pathogen.

10. The method of claim 1, wherein the at least one bacterial or fungal pathogen comprises a plant pathogen, and wherein the method comprises bacterizing a plant or coating food or a plant with the bacterium, preferably wherein the plant is a tomato plant or a lettuce plant.

11. (canceled)

12. The method of claim 1, wherein the at least one bacterial pathogen comprises a biofilm producing bacterial pathogen, preferably a Salmonella such as a Salmonella enterica.

13. (canceled)

14. (canceled)

15. The method of claim 1, wherein the method uses the biosurfactant-containing extract isolated from said bacterium, preferably an acid precipitate fraction of the biosurfactant-containing extract.

16. (canceled)

17. A plant or plant part bacterized or coated with a Bacillus or a biosurfactant-containing extract isolated from the Bacillus.

18. The plant or plant part of claim 17, wherein the Bacillus is a Bacillus velezensis.

19. The plant or plant part of claim 17, wherein (i) the Bacillus produces, or the biosurfactant-containing extract contains at least 3 of bacilysin, difficidin, macrolactin H, bacillaene, bacillomycin D, fengycin, surfactin and bacillibactin; or (ii) the Bacillus encodes at least 10 of SEQ ID NOs: 1-111.

20. (canceled)

21. The plant or plant part of claim 17, wherein the Bacillus is Bacillus velezensis OB9.

22. The plant or plant part of claim 17, which is a tomato or a lettuce plant, plant part or cell.

23. A method of protecting a plant or plant part against at least one bacterial or fungal pathogen comprising bacterizing or coating the plant or plant part with a Bacillus or a biosurfactant-containing extract isolated from the Bacillus, wherein the Bacillus produces or the extract contains at least 3 of bacilysin, difficidin, macrolactin H, bacillaene, bacillomycin D, fengycin, surfactin and bacillibactin.

24. The method of claim 23, wherein the Bacillus is a Bacillus velezensis.

25. The method of claim 23, wherein (A) (i) the Bacillus encodes at least 10 of SEQ ID NOs: 1-111; and/or (B) the method comprises (i) bacterizing or coating the plant; or (ii) bacterizing or coating the plant part.

26. The method of claim 23, wherein the Bacillus is a Bacillus methylotrophicus OB9.

27. (canceled) 28. (canceled)

29. The method of claim 23, wherein the at least one bacterial or fungal pathogen comprises a Salmonella, an Escherichia coli, an Enterobacteriaceae, an Xanthomonas campestris, a Rhizoctonia solani or a Botrytis cinereal.

30. The method of claim 23, wherein the at least one bacterial pathogen comprises a Salmonella or a Xanthomonas campestris.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In the appended drawings:

[0073] FIGS. 1A-C. Distribution of bacterial genera in three oil wells. The numbers in each pie chart represent the isolates of each genus. The numbers in brackets represent the abundance of bacterial isolates of each genus relative to the total number of isolates recovered from each oil well. (FIG. 1A) Well 10-22, (FIG. 1B) Well 5-27, and (FIG. 1C) Well 10-17. Data represent the average of three-replicate samples.

[0074] FIGS. 2A-B. The antimicrobial activities of B. methylotrophicus OB9 (B.m.OB9) against plant and foodborne pathogens. (FIG. 2A) Confrontation co-culture assay with the fungal plant pathogen, Rhizoctonia solani. (FIG. 2B) Agar diffusion assays with Xanthomonas campestris B07.007 (X. campestris), Salmonella enterica subsp. enterica Newport SL1 (S. enterica), Escherichia coli E14-6 (E. coli). The (−ve) series denotes confluent growth of each organism on the control plates, while in the (+ve) series (Diffusion Agar Assay) the same organisms were challenged with B. methylotrophicus OB9 (as noted by the zone of clearing around B. methylotrophicus OB9).

[0075] FIGS. 3A-C. Thin layer chromatography (TLC) separation and biosurfactant assessment of cell free supernatant (CFS) and acid precipitate fraction (APF) extracts from B. methylotrophicus OB9.(FIG. 3A) TLC plate exposed to UV light with fraction numbers and Rf values denoted for CFS and APF preparations. The biosurfactant properties of TLC-isolated APF fractions of B. methylotrophicus OB9 were analyzed by the drop collapse assay (FIG. 3B) with APF fractions 1-5 and Triton™ X-100 (T) as a control and the oil spreading assay (FIG. 3C) with APF fractions 1-5, water (W) and Triton™ TM X-100 (T).

[0076] FIGS. 4A-E. Antimicrobial assessment of APF extracts from B. methylotrophicus OB9. (FIG. 4A) Antimicrobial activity of APF fractions F3 and F5 with the agar diffusion assay against Salmonella Typhimurium producing four biofilm morphotypes. From left to right: column 1 contains negative controls (-ve) for growth of each of the four strains (rows 1-4 are UMR1, MAE14, MAE299 and MAE775, respectively); columns 2-4 contain the same strains, but assayed against fraction 3 (F3), fraction 5 (F5) or bleach as positive control (+ve), respectively. FIGS. 4B-D: Additional diffusion assays of F3, F5, 1% (v/v) acetic acid, and 1% lactic acid against Salmonella agona PARC #5 (designated S. enterica strain A) (FIG. 4B), Salmonella serovar I:Rough-O:e,h:e,n (designated S. enterica strain B) (FIG. 4C) and E. coli E14-6 (E. coli) (FIG. 4D). In FIGS. 4B-D, upper panels show fractions F3 and F5 with the noted bacteria and the lower panels show fractions F3 and F5 with the noted bacteria and acetic acid or lactic acid. FIG. 4E shows the antagonistic effect of F3 and F5 against Rhizoctonia solani (top two panels), while the bottom two panels display negative control growth (−) and APF fraction 5 (F5) assayed Botrytis cinerea. Antimicrobial assessment of APF was conducted three times.

[0077] FIGS. 5A-D. Suppression of Salmonella and Xanthomonas growth in co-cultures with B. methylotrophicus OB9. FIGS. 5A-B: Temporal microbial counts of Salmonella enterica Newport (SL1) (FIG. 5A) and Bacillus methylotrophicus (B.m. OB9) (FIG. 5B) in single cultures and in co-cultures with OB9 over 72 hours. FIGS. 5B-C: Temporal microbial counts of Xanthomonas (FIG. 5C) and OB9 (FIG. 5D) in single cultures and in co-cultures with B. methylotrophicus OB9 over 72 hours.

[0078] FIGS. 6A-D. Suppression of Salmonella enterica subsp. enterica Newport SL1 (S. enterica) and Xanthomonas campestris B07.007 (X. campestris) growth in bacterized plants with Bacillus methylotrophicus OB9 (B.m. OB9). (FIG. 6A) Control treatment (tomato+S. enterica subsp. enterica Newport SL1 (S. enterica)) displays a tomato seedling in tissue culture infected with S. enterica. Recovery of S. enterica cells on culture medium from a detached leaf (shown) infected with S. enterica representative of CFU/gram tissue is depicted on the agar plate. (FIG. 6B) Treatment (Tomato+B.m. OB9+S. enterica) consisting of a tomato seedling in tissue culture bacterized with Bacillus methylotrophicus OB9 (B.m. OB9) and infected with S. enterica. Recovery of B.m. OB9 cells from a detached bacterized leaf (shown) infected with S. enterica (B.m. OB9+S. enterica) representative of CFU/gram tissue is depicted on the agar plate. (FIG. 6C) Control treatment (Lettuce+X. campestris) showing a lettuce seedling in tissue culture infected with X. campestris B07.007 and an infected detached leaf is shown. Recovery of X. campestris cells on culture medium from a detached leave (shown) infected with X. campestris representative of CFU/gram tissue is depicted on the agar plate. (FIG. 6D) Treatment (Lettuce+B.m.OB9+X. campestris) of a lettuce seedling in tissue culture bacterized with B.m. OB9 and infected with X. campestris B07.007. Recovery of B.m. OB9 cells but not X. campestris cells on culture medium from a detached bacterized leave (shown) infected with X. campestris representative of CFU/gram tissue is depicted on the agar plate.

[0079] FIGS. 7A-D. Quantification of cell numbers of B. methylotrophicus OB9 (B.m. OB9), Salmonella enterica subsp. enterica Newport SL1 (S. enterica) and Xanthomonas campestris B07.007 (X. campestris) recovered from leaf tissues. Leaf tissues bacterized with B.m.OB9 and challenged with S. enterica (FIG. 7A) and X. campestris (FIG. 7B). FIGS. 7C-D: Tomato and lettuce leaf samples that were coated with B.m. OB9 and infected with S. enterica (FIG. 7C) and X. campestris (FIG. 7D). (BI) and (CI) samples represent B.m. OB9bacterized (BI) or coated (CI) tissues that are infected with either S. enterica or X. campestris. (NBI) and (NCI) treatments represent non-bacterized and non-coated plant samples that were infected with S. enterica or X. campestris controls, respectively. Data represent the average of 5 replicates per treatment.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0080] The present disclosure is illustrated in further details by the following non-limiting examples.

EXAMPLE 1: MATERIALS AND METHODS

Source of Crude Oil Samples and Organisms

[0081] Crude oil samples were obtained from the operating area of Talisman Energy Inc., which is located in Chauvin, Alberta. The inventors were provided with duplicate samples representing pooled samples from wells of each of the three batteries (battery 10-22, battery 5-27 and battery 10-17), using sterile 500 mL Schott bottles tightly sealed, kept on ice during transportation and stored at 4° C. for DNA extraction (Table II, below). The physical and chemical characteristics of the crude oil are listed in Table II. Target organisms, consisting of a panel of 41 bacterial and fungal strains (listed in Table III, below), were tested in dual diffusion assays with biosurfactant-producing strains. Salmonella enterica subsp. Enterica strains belonging to 17 different serovars, including top clinical serovars (e.g., Typhimurium, Heidelberg, Newport, Infantis, Thompson and Braenderup) and environmental samples, were classified according to the four Salmonella biofilm morphotypes displayed on congo red plates (Römling et al., 1998). Strains with the morphotypes: rdar (red dry and rough) are cellulose and curli positive, pdar (pink dry and rough) are cellulose positive, bdar (brown dry and rough) are curli positive and saw (smooth and white) are negative for both components.

TABLE-US-00002 TABLE II Physical and chemical properties of oil samples from oil batteries 10-22, 5-27, and 10-17 Location Properties Chauvin, Alberta Chauvin, Alberta Chauvin, Alberta Oil Battery 10-22 5-27 10-27 Number of 36 119 162 wells.sup.a pH 7.4 7.4 7.4 Specific gravity 1.06 kg/m.sup.3 1.06 kg/m.sup.3 1.06 kg/m.sup.3 Water content 0.40% 0.29% 0.14% Absolute 955.1 kg/m.sup.3 917 kg/m.sup.3 946.7 kg/m.sup.3 density API gravity 16.6 kg/m.sup.3 22.8 kg/m.sup.3 17.9 kg/m.sup.3 Sulphur 25.3 g/kg 24.7 28.7 g/kg Total solids 81315 mg/lt 82900 mg/lt 86159 mg/lt dissolved Viscosity 863 mPas 87.05 mPas 644.5 mPas .sup.aRecovery and isolation of microbes were pooled from duplicate oil samples provided from each battery.

TABLE-US-00003 TABLE III Source of organisms Biofilm formation Number Strain ID Identity at 28° C. Origin/morphotype Source/provider BACTERIA Salmonella strains/morphotypes 1 UMR1 Salmonella typhimurium rdar* Control 1 2 MAE14 S. typhimurium pdar* Control 1 3 MAE299 S. typhimurium bdar* Control 1 4 MAE775 S. typhimurium baw* Control 1 5 S1V1 Salmonella sp. pdar Environment 1 6 S3PP Salmonella sp. saw Environment 1 7 S13V2 Salmonella sp. rdar Environment 1 8 S2V3 Salmonella sp. rdar & saw Environment 1 9 S1V3 Salmonella sp. saw Environment 1 10 S4V2 Salmonella sp. pdar & saw Environment 1 11 S10V1 Salmonella sp. pdar Environment 1 12 S12PP Salmonella sp. rdar Environment 1 13 S18V2 Salmonella sp. pdar & saw Environment 1 14 S2V2 Salmonella sp. Combination Environment 1 15 SC01 Salmonella Serotype rdar Environment 1 I: 4, 5, 12: b: 16 SC16 Salmonella Serotype saw Environment 1 I: Rough-O:: e, n, x 17 SC04 Salmonella Serotype rdar Environment 1 Braenderup 18 SCS7 Salmonella Serotype saw Environment 1 Typhimurium 19 SC110 Salmonella Serotype rdar Environment 1 I: RoughO: y: e, n, x 20 SC12 Salmonella Serotype rdar Environment 1 I: Rough-O: e, h 21 SC18 Salmonella Serotype rdar Environment 1 Hartford 22 SCS2 Salmonella rdar Environment 1 Serotype: RoughO: e, h: e, 23 WTCR5 Salmonella Serotype rdar/saw Environment 1 I: 6, 7: r 24 WTCR6 Salmonella Serotype rdar/saw Environment 1 Stanley 25 WTCR9 Salmonella Serotype rdar/saw Environment 1 Infantis 26 WTCR30 Salmonella Serotype- rdar/saw Environment 1 Schwarzengrund 27 WTCR22 Salmonella Serotype rdar/saw Environment 1 Thompson 28 WTC27 Salmonella serotype saw Environment 1 Heidleberg 29 WTC28 Salmonella Serotype rdar/saw Environment 1 Monschaui 30 WTCT4 Serotype Heidleberg rdar/saw Environment 1 31 PARC#5 S. agona rdar/saw Mung bean 3 32 SL1 S. Newport rdar Human gut 2 33 SL2 S. Hartford rdar Human gut 2 Escherichia species 34 E3-6 Escherichia coli NA NA 1 35 E10-6 E. coli NA NA 1 36 E14-6 E. coli NA NA 1 37 E15-6 E. coli NA NA 1 Xanthomonas sp. 38 B07.007 Xanthomonas campestris rdar Lettuce 4 pv. vitians FUNGI Rhizoctonia sp. 39 AG3-114 R. solani NA Potato 5 40 AG1-1-ROS- R. solani NA Soybean 6 2A4) Botrytis 41 F-014 Botrytis cinerea NA Strawberry 7 *Strains displaying rdar (red dry and rough) are cellulose and curli positive, strains displaying pdar (pink dry and rough) are cellulose positive, strains displaying bdar (brown dry and rough) are curli positive, and strains displaying saw (negative for both components) are negative for both components, NA: not applicable. 1. J. Weadge, Wilfrid Laurier University, Ontario; U. Romling et al., (2003). Int. J. Med. Microbiol. 293, 273-285. 2. S. Bekal, The Laboratory of Public Health of Quebec (QPHL), Quebec. 3. S. Orban, Agriculture and Agri-Food Canada (AAFC), BC. 4. V. Toussaint, AAFC, St. Jean sur Richelieu, Quebec. 5. M. A. Cubeta , N.C. States University, NO, USA. 6. P. Ceresini, UNESP Sao Paolo, Brazil. 7. S. Jabaji, McGill University, Quebec.

Isolation of Oil-Dwelling Bacteria

[0082] Unless otherwise stated, manipulation of oil samples was performed under sterile conditions in the laminar flow hood in order to avoid any contamination. Crude oil samples (10 mL of each) were mixed with an equal volume of sterile distilled water. The emulsion was vortexed and then continuously agitated (2×g) on a rotary shaker for 2 h, before the aqueous phase was recovered with a sterile pipette. This procedure was repeated five times, collecting a total of 50 mL of the aqueous phase for each sample from each well. Aliquots (100 μL) of the aqueous phase were plated on different microbiological culture media; potato dextrose agar (PDA), malt extract agar (MEA), nutrient agar (NA) and lysogeny broth agar (LBA) (BDH chemical Ltd, Mississauga, ON, Canada), and incubated at 28° C. Bacterial colonies that grew on culture media were passed through four rounds of single colony isolation by streaking them on the above-mentioned culture media to ensure purity of each strain prior to long-term storage. Pure bacterial cultures were stored in 20% (v/v) glycerol and kept at −80° C. until further use.

Molecular Identification of Bacteria Recovered from Oil Bacterial strains were grown in LB broth for 18 h with agitation to obtain a final concentration of 10.SUP.8.-10.SUP.10 .colony forming units (CFU) mL.SUP.−1.. Cells were pelleted by centrifugation, and DNA was extracted using the DNeasy® Blood & Tissue kit (Qiagen, Mississauga, Ontario) following the manufacturer's instructions. DNA concentration and quality were confirmed spectrophotometrically with a NanoDrop™ ND1000 spectrophotometer (NanoDrop, Wilmington, Del. USA) and on a 1% (w/v) agarose gel, respectively. The 16S rRNA gene sequences were amplified using the ITS primer pair 27F/534R (5′-AGAGTTTGATCCTGGCTCAG-3′) (SEQ ID NO: 112) and 534R (5′-ATTACCGCGGCTGCTGG-3′) (SEQ ID NO: 113) according to previously published protocols (Gagne-Bourgue et al., 2013; Scott et al., 2018) to putatively identify 123 bacterial strains. PCR amplification was performed in a Bio-Rad™ T100 Thermal Cycler using the iProof™ High-Fidelity (HF) PCR kit (Bio-Rad, Ontario, Canada) using 40 ng of genomic DNA for a 50 μL reaction following previously published protocols (Gagne-Bourgue et al., 2013; Scott et al., 2018). Negative and positive controls were included concurrently with each reaction according to previous protocols (Scott et al., 2018). Amplification of PCR products was confirmed on a 1% (w/v) agarose gel. Lower molecular weight PCR products were cloned into the pDrive™ vector (Qiagen) following the manufacturer's protocol. Purified plasmid DNA and PCR products were sequenced at Genome Quebec sequencing services (McGill University, Montreal, QC, Canada). Sequences were subjected to Blast™ search against the NCBI database using the algorithm megablast (http://www.ncbi.nlm.nih.gov/blast) to confirm identity through sequence homology. The obtained sequences were submitted NCBI GenBank.

Enrichment of Biosurfactant Production by Oil-Dwelling Bacteria

[0083] For efficient degradation of complex hydrocarbon oil and the production of biosurfactants, 3.27 g/L of Bushnell and Haas (BHM) (BDH chemical Ltd) supplemented with 2% of each of crude oil (v/v), glucose (w/v) and molasses (v/v) as sole sources of carbon, adjusted to pH 7.0 and sterilized at 21 psi for 20 min was used. A 1 mL volume of bacterial cultures (grown at 22° C. for 18-24 h with agitation in LB broth) with an OD.sub.600 between 0.6 and 1.0 was transferred to 100 mL of the carbon-amended BHM media. Inoculated media was incubated with continuous agitation (2×g) at 30° C. for 7 d and then the cell-free supernatant (CFS) was collected by centrifugation (6500×g at 4° C. for 20 min). Removal of any residual oil and/or live bacterial cells present in the cell-free supernatant was accomplished by filtration using a 0.22 μm Millipore™ filter (Millipore Sigma, Ontario, Canada) and kept at 4° C. until further use.

Assays for Biosurfactant Production

[0084] Bacterial isolates originating from oil batteries (10-22, 5-27 and 10-17) were screened for biosurfactant production by applying the most commonly used assays in the literature; the oil-spreading test and drop-collapse assay (Thavasi, 2011; Youssef et al., 2004). Isolates were considered to have significant biosurfactant production if the clearing zone they produced was at least ≤1.0 cm in diameter in the oil spreading assay and ≤3.0 mm in the drop collapse assay (Youssef et al., 2004). In all assays unless otherwise stated, Triton™ X-100 (10 mg/mL) was used as the positive control, while sterile de-ionized water and un-inoculated hydrocarbon-amended BHM medium served as negative controls. All tests were replicated twice for each bacterial strain tested. Based on the above-mentioned criteria, the top biosurfactant producers were further screened using the CTAB agar method, emulsification assay, microplate assay, and hemolytic assay.

[0085] Drop collapse assay. The wells of a polystyrene 96 well micro-plate lid (Corning incorporated, USA) were coated with 2 μL of crude oil and left to dry for 24 h at 22° C. Filtered cell-free supernatant (5 μL) was transferred to the center of the oil coated well. The results were recorded after 1-2 min and considered positive for biosurfactant production when the oil drop was flat. Those that gave rounded drops were scored negative, an indication of the absence of biosurfactant production (Jain et al., 1991).

[0086] Oil spreading assay. The oil-spreading assay was performed in polystyrene petri dishes (100 mm×15mm) containing 20 μL of crude oil that was carefully layered over 20 mL of distilled water. A drop (˜10 μL) of filtered supernatant was carefully pipetted onto the center of the oil layer. The diameter of the clear zone on the surface of the oil layer was measured and compared to the negative controls (Ibrahim et al., 2013).

[0087] CTAB agar assay. CTAB agar plates were prepared by adding 0.15 g of cetyltrimethylammonium bromide (CT-Aldrich, Oakville, Ontario, Canada), 0.005 g Methylene blue (Sigma-Aldrich) and 12 g of agar to 1 L of distilled water, adjusted to pH 7 and sterilized (Tahzibi et al., 2004). Two holes (6.5 mm diameter) were made in the CTAB plates, and approximately 150 μL of filtered cell-free supernatant was loaded inside each hole. Plates were incubated at 37 ° C. for 48 h. Cell free supernatant containing anionic surfactant produced blue halos around the wells in which they were placed. The diameter of the halo was measured and compared with positive and negative controls.

[0088] Emulsification assay. A volume of 1 mL of the cell-free supernatant was added to 5 mL of 50 mM Tris buffer (pH 8.0) in a 30 mL screw-capped test tube. Crude oil was tested for emulsification activity. Crude oil (5 mg) was added to both layers and vortexed for 1 min and then the emulsion mixture was allowed to settle for 20 min. The optical density of the emulsified mixture was measured at 610 nm (Muthezhilan et al., 2014). A negative control consisted of only buffer solution and crude oil with Triton™ X-100 was used as the positive control.

[0089] Microplate assay. An aliquot of 50 μL of filtered cell-free supernatant was placed in domed PCR caps (Ultident Scientific, St. Laurent, Quebec, Canada) that were oriented over a grid of 1 mm×1 mm squares. The presence of biosurfactant was confirmed by the distortion of the grid image and were qualitatively compared to the positive and negative controls (Walter et al., 2010).

[0090] Hemolytic activity. Blood agar plates were prepared by adding 5% (v/v) of sheep blood (Fisher scientific) to a sterilized mixture of NaCl (10 g), yeast (5 g), tryptone (10 g) and agar (15 g) in 1 L of distilled water (Phan et al., 2013). Approximately 150 μL of filtered cell free supernatant of each bacterial isolate was loaded into each well (6.5 mm in diameter) made by a cork borer in the blood agar plates and incubated at 30° C. for 24-48 h. Biosurfactant biosynthesis was confirmed by hemolysis activity as indicated by the presence of clearing zones around the wells. The diameter of the lysis zone was scored as ‘−’ no lysis, ‘+’ partial hemolysis, ‘++’ moderate hemolysis , ‘+++’ complete hemolysis.

[0091] Antimicrobial Activity of Whole Cultures of B. methylotrophicus OB9

[0092] Isolate OB9 exhibited the highest activity for oil displacement and emulsification activity. This strain was identified as B. methylotrophicus based on sequencing data and hereby designated as B. methylotrophicus OB9 (Jeukens et al., 2015). This strain was further screened for its antimicrobial activity against a wide panel of clinical and environmental bacterial strains (Table V) employing the Burkholder agar diffusion assay (Burkholder et al., 1944), and also against fungal phytopathogens using the dual confrontation assay (Gagne-Bourgue et al., 2013).

TABLE-US-00004 TABLE IV Top biosurfactant-producing isolates of three oil wells 10-22, 5-27, 10-17 OIL DROP GENBANK STRAIN SPREADING COLLAPSE ACCESSION RANK NAME ID (CM)* (MM)** NUMBER Well 10-52 1 Bradyrhizobium sp. OB55 .sup. 1.6 ± 0.1& 3.5 ± 0.0 MG926629 2 Streptomyces sp. OB45 1.6 ± 0.7 3.0 ± 0.0 MG926620 3 Streptomyces sp. OB44 2.0 ± 0.6 3.5 ± 0.0 MG926618 4 Bacillus amyloliquefaciens OB10 2.1 ± 0.2 3.5 ± 0.0 MG926639 5 Bacillus nealsonii OB51 2.6 ± 0.0 4.0 ± 0.0 MG926626 6 Microbacterium sp. OB14 2.3 ± 0.2 3.5 ± 0.0 MG926642 7 Bacillus methylotrophicus OB43 2.4 ± 0.7 3.5 ± 0.0 MG926614 8 Streptomyces yanglinensis OB41 2.6 ± 0.1 3.5 ± 0.0 MG926610 9 Bacillus amyloliquefaciens OB5 3.2 ± 0.3 3.8 ± 0.3 MG924914 10 Streptomyces sp. OB42-1 3.3 ± 0.1 3.5 ± 0.1 MG926612 11 Bacillus amyloliquefaciens OB6 3.6 ± 0.3 4.3 ± 0.3 MG926633 12 Bacillus velezensis OB9 3.8 ± 0.1 4.3 ± 0.6 MG926638 (previously methylotrophicus) Well5-27 1 Bacillus simplex E05 1.5 ± 0.0 3.5 ± 0.0 MG946778 2 Micrococcus testaceum E47 1.5 ± 0.2 3.3 ± 0.1 MG926596 3 Rhodococcus sp. E51-2 1.6 ± 2.7 3.5 ± 0.0 MG627949 4 Bacillus methylotrophicus E62 1.7 ± 0.3 3.7 ± 0.2 MG946778 5 Pseudomonas sp. E14 2.2 ± 0.1 4.8 ± 0.3 MG946770 6 Bacillus subtilis E64 2.0 ± 0.2 3.8 ± 0.3 MG946784 7 Bacillus subtilis E68 2.6 ± 0.3 3.8 ± 0.0 MG946779 8 Arthrobacter sp. E45 2.9 ± 0.4 4.2 ± 0.3 — Well 10-17 1 Bacillus methylotrophicus M16-3 2.2 ± 0.0 3.4 ± 0.1 MH627955 2 Bacillus subtilis M46-2 2.6 ± 0.1 3.3 ± 0.1 MH627971 3 Bacillus methylotrophicus M05-2 2.7 ± 0.2 3.4 ± 0.1 MH627945 4 Bacillus subtilis M43 2.9 ± 0.1 3.4 ± 0.2 MH627966 5 Bacillus amyloliquefaciens M36 2.9 ± 0.1 3.4 ± 0.2 MH627961 6 Bacillus amyloliquefaciens M27 3.0 ± 0.1 3.2 ± 0.1 MH627959 7 Bacillus velezensis M50 3.0 ± 0.1 3.4 ± 0.1 MH627972 8 Kokuria rhizophila M20 3.1 ± 0.1 3.5 ± 0.0 MH627956 9 Staphylococcus saprophyticus M44 3.1 ± 0.0 3.2 ± 0.1 MH627967 10 Bacillus velezensis M05 3.2 ± 0.2 3.4 ± 0.1 MH627944 11 Bacillus amyloliquefaciens M30 3.4 ± 0.1 3.4 ± 0.1 MH627960 12 Bacillus velezensis M09 3.4 ± 0.0 3.4 ± 0.2 MH627948 13 Bacillus velezensis M21 3.4 ± 0.1 3.2 ± 0.1 MH627957 14 Bacillus subtilis M42 3.5 ± 0.0 3.2 ± 0.1 MH627965 *For oil spreading assay clearing zone of ≥1.5 cm is considered positive. **For drop collapse assay above ≥3 mm is considered positive &Values represent the mean of three replicates ± standard error of the mean (S.E.)

[0093] Agar diffusion assay. All target bacterial strains and B. methylotrophicus OB9 were grown in LB broth at 27° C. for 16-18 h with constant shaking to achieve mid-log phase, with a cell density of 10.sup.6 CFU mL.sup.−1 as assessed based on standard curves relating optical density at 600 nm (OD.sub.600) to plate counts on LBA plates. Cells were pelleted by centrifugation (6500×g at 4° C. for 20 min. and suspended in sterile ddH.sub.2O. A total volume of 30 μL of each bacterial suspension was mixed gently with 2.5 mL of molten half-strength LB agar and poured into culture plates. An aliquot (10 μL) of B. methylotrophicus OB9 was spotted in the center of the bacterial lawn and plates were incubated at 24° C. Zones of bacterial growth-inhibition subjacent to the spotted B. methylotrophicus OB9 inoculum were recorded after 24-48 h and were found to vary in diameter between 3 to 6 mm depending on the potency of B. methylotrophicus OB9 antimicrobials that diffused into the agar. Individual trials were performed in triplicate and the entire assay was repeated twice to confirm the findings.

[0094] Dual confrontation assay. Confrontation assay plates were used to screen B. methylotrophicus OB9 for its ability to inhibit radial growth of Botrytis cinerea, and Rhizoctonia solani isolates according to the modified method of Gagné-Bourgue (Gagne-Bourgue et al., 2013). PDA plates were inoculated in the center with a 5 mm diameter mycelial plug taken from the edge of an actively growing fungal colony. A 5 μL volume of B. methylotrophicus OB9 (10.sup.6 CFU mL.sup.−1) was deposited 25 mm on either side of the fungal colony. Triplicate plate assays were performed for each target fungal organism and radial growth inhibition of the fungus was measured 5 d post confrontation.

Purification and Fractionation of Biosurfactants of B. methylotrophicus OB9 by Thin Layer Chromatography (TLC)

[0095] The biosurfactant-producing B. methylotrophicus OB9 was cultured in 2 L of BHM broth supplemented with 2% (w/v) glucose, 2% (v/v) molasses and 2% (v/v) oil for 7 d with agitation (2×g) at 30° C. Bacterial cells were removed by centrifugation (5000×g at 4° C.) and the cell—free supernatant (CFS) was acidified to pH 2.0 with 2N HCL at 4° C. for 16 h resulting in a precipitate that was collected by centrifugation (5000×g for 10 min at 4° C.). The acid precipitate fraction (APF) was dissolved in water (100 mg/mL) and adjusted to pH 7.0 using 1N NaOH. The CFS sample and clean BHM culture medium were concentrated by freeze-drying for 48 h. All samples were stored at −80° C. until further use.

[0096] Separation of CFS and APF fractions was performed by thin layer chromatography (TLC). Acid-cleaned glass plates (20×20 cm) were coated with a thin layer of silica emulsion (160 grams of silica with 15% (w/v) calcium sulphate and with fluorescent indicator GF254 dissolved in 500 mL of double distilled water) purchased from Sigma-Aldrich and dried for 16-18 h at 22° C. Activation of silica plates was done by heating the TLC plates at 120° C. for 30 min prior to use. An amount of 100 mg of each of CFS and APF were dissolved in 400 μL of chloroform: methanol (2:1, v/v) and separated on activated TLC plates with chloroform: methanol: water (70:26:4) as the developing solvent system. Plates were observed under UV (λ=254 nm) and the retention factor (Rf) values were calculated as distance travelled by the samples over the distance travelled by solvent. Only APF separated fractions were used for bioactivity assays. Bands corresponding to the desired Rf values were scraped and collected for extraction. Bands of the same Rf value from different plates were pooled together and extracted twice with chloroform: methanol (v/v/; 2:1). The collected fractions were vacuum-concentrated for 4-6 h at −60° C. using a Speed Vac™ v78100 (Labconco Corp, Kansas City Mo., USA), re-dissolved in 50 μL of methanol and tested against target bacteria and fungi, as well as for biosurfactant activity. Methanol (50 μL) was used as a negative control.

Biosurfactant and Antimicrobial Activities of TLC Fractions

[0097] The biosurfactant activity of the fractions was tested using the oil-spreading and the drop collapse methods, as described above. Fractions were also tested for their antimicrobial activities against a number of bacteria and fungi using the Burkholder diffusion plate method as noted above. Briefly, 10 μL of the dissolved fractions were spotted in the middle of the plates. Positive controls consisted of 10 μL of bleach and of each of the following organic acids: 1% (v/v) of acetic acid, formic acid, citric acid and lactic acid. All plates were incubated at 24° C. and a clearing zone of 3 mm or greater after 24 h of incubation was considered positive for inhibition of growth. Individual trials were performed in triplicate and the entire assay was repeated twice to confirm the findings.

Interaction of B. methylotrophicus OB9 with S. enterica Newport SL1 and X. campestris B07.007 in Liquid Co-Culture

[0098] This method was performed to study how B. methylotrophicus OB9 directly interacts with target strains of Salmonella enterica Newport SL1 and X. campestris B07.007. Each bacterium was grown in LB broth until a cell density of 10.sup.6 CFU mL.sup.−1 was achieved, as assessed based on standard curves relating optical density at 600 nm (OD.sub.600) to plate counts on LBA plates. An equal volume of B. methylotrophicus OB9 culture and target organisms (Salmonella or Xanthomonas) was added to fresh LB liquid culture amended with 3% (w/v) yeast extract. Pure cultures of Salmonella enterica Newport SL1, X. campestris and B. methylotrophicus OB9 grown in amended LB broth served as positive controls. Liquid co-cultures and controls were incubated with agitation (2×g) at 28° C. To avoid changes in growth during co-culturing due to pH variation or nutrient limitations, every 10 h liquid co-cultures and controls were subjected to centrifugation (15 min at 5000×g) and bacterial pellets were suspended in fresh amended LB medium. Serial dilutions (10.sup.−3 to 10.sup.−5) from control and liquid co-cultures were plated on LBA after 3, 6, 12, 24 and 72 h of incubation, estimated as log.sub.10 CFU mL.sup.−1 and compared to the control treatments. There were three replicates per target organism and treatment. Individual trials were also repeated at least twice.

Bacterization and Internalization of B. methylotrophicus OB9 in Tissue Cultured Tomato and Lettuce Seedlings.

[0099] Vegetable cultivars. Organic Tomato (cv. Beefsteak) and Cos lettuce (cv. Parris Island) seeds (Vesey seed Ltd, York, PE, Canada) were surface sterilized using 70% (v/v) ethanol and 1.3% (v/v) sodium hypochlorite in a stepwise procedure according to Scott et al., 2018. The seeds were transferred to tissue culture tubes (25 mm×150 mm; VWR, PA, USA) containing 10 mL of Murashige and Skoog (MS) medium supplemented with 3% (w/v) sucrose (Gagné-Bourque et al., 2015). Tissue culture tubes were incubated under 200 μmol m.sup.−2 s.sup.−1 white fluorescent light, 18/6-h photoperiod, and 24° C. day/night temperature for 2 weeks.

[0100] Preparation of B. methylotrophicus 0B9 inoculum. Inoculum of B. methylotrophicus OB9 was prepared by transferring a single colony to 100 mL of LB broth and incubating with agitation (2×g) at 28° C. Bacterial cells were harvested by centrifugation (4500×g for 15 min at 4° C.), washed with10 mM phosphate buffer (PBS) containing 0.8% (w/v) NaCl, pH 6.5 (phosphate buffered saline or PBS) and then suspended in the same buffer following another round of centrifugation (Pillay et al., 1997). The density of the B. methylotrophicus OB9 suspension was adjusted to 10.sup.6 CFU mL.sup.−1 as described above.

[0101] Bacterization of plant seedlings with B. methylotrophicus OB9. A 500 μL volume of B. methylotrophicus OB9 in PBS buffer was carefully dispensed on the surface of the MS media and close to the roots of 2-week-old tomato and lettuce seedlings. Non-bacterized seedlings received 500 μL of PBS only and served as negative controls. Inoculated and control seedlings were returned to the environmental growth chamber and grown for 2 more weeks. The experimental unit was an individual plant contained in a test tube (a replicate) and 5 replicates per treatment were evaluated in two separate experimental trials. Bacterial populations were transformed to obtain homogeneity of variances and expressed as log.sub.10 (CFU per leaf fresh weight).

[0102] Colonization, internalization and retrieval of B. methylotrophicus OB9 from plant tissue. Recovery and colonization of plant tissues by B. methylotrophicus OB9 was confirmed by culture-dependent (cell count) and culture-independent (PCR assay) methods. Cell counts (CFU mL.sup.−1) were estimated 2 weeks post inoculation (wpi). Root and leaf tissues (100 mg of each) of tomato and lettuce seedlings were surface sterilized as described above to ensure that only B. methylotrophicus OB9 that had internally colonized plant tissues remained. The efficiency of the sterilization procedure was tested using the imprint method and absence of growth on the imprinted culture medium indicated that the surface sterilization procedure was effective. Surface sterilized tissues (100 mg) were ground in sterile distilled water, serially diluted (10.sup.−1 to 10.sup.−7) and spread on LBA plates to assess the presence of B. methylotrophicus OB9. The presence of B. methylotrophicus OB9 inside plant tissues was also confirmed by PCR amplification. Briefly, bacterized Plant DNA (200 mg) was reduced to powder in liquid nitrogen and genomic DNA was extracted using the CTAB extraction method (Huang et al., 2011; Porebski et al., 1997) that targeted the bacterial DNA in the plants. Genomic DNA from pure colonies of B. methylotrophicus OB9 was extracted and PCR was performed (Huang et al., 2011). The presence of B. methylotrophicus OB9 DNA in plant tissue was detected using specific primers [5′-CAAGTGCCGTTCAAATAG-3′ (SEQ ID NO: 114) (Forward) and 5′CTCTAGGATTGTCAGAGG-3′ (SEQ ID NO: 115) (reverse)] in 25 μL PCR reactions using 20 ng of DNA. The amplification and PCR conditions are described in detail in (Gagné-Bourque et al., 2015).

Protection of Tomato and Lettuce Leaves by B. methylotrophicus OB9 from Salmonella and Xanthomonas

[0103] Preparation of Salmonella and Xanthomonas for leaf inoculation. Salmonella enterica Newport SL1 (isolated from human gut) and X. campestris B07.007 (isolated from lettuce) were prepared by separately transferring a single colony of each strain into 100 mL of LB broth and incubating with agitation (2×g) at 28° C. Bacterial cells were harvested, and the density of each culture was adjusted to 10.sup.6 cells mL.sup.−1 following the same procedures described for B. methylotrophicus OB9 cells above. Two separate experiments were set up to study the effect of B. methylotrophicus OB9 on growth of Salmonella and Xanthomonas on plants.

Statistical Analysis

[0104] In the co-culture experiment, there were three replicates per target organism and treatment, and the assays were repeated twice. In the tissue culture experiments (experiment 1 and experiment 2), each experimental unit consisted of one leaf per petri plate (one replicate). There were 5 replicates per treatment, and the entire experiment was repeated twice. Data of bacterial cell counts in co-culture and in tissue-culture experiments (Experiments 1 and 2) were analyzed by One-way ANOVA using the JMP 13.0 software. All experimental data were tested for statistical significance using Tukey's HSD (P≤0.05).

EXAMPLE 2: BACTERIAL DIVERSITY OF CRUDE OIL-INHABITING BACTERIA

[0105] A total of 123 culturable bacteria, originating from crude oil samples were isolated from 3 oil batteries. A snapshot of the bacterial species in each oil battery, based on 16S rRNA gene sequences, indicated that the oil-inhabiting bacterial community is diverse (FIGS. 1A-C) and composed predominantly of bacteria (the majority identified to the species level) from 3 phyla (Actinobacteria, Proteobacteria, and Firmicutes) along with 17 discrete genera that shared high homology with known sequences. The full sequences of all strains have been deposited to GenBank under the following accession numbers (battery 10-22 MG924907-MG924915 and MG926585-MG92664, battery 10-17 MH627942-MH627972, and battery 5-27 MG946770-MG946789, and MG951760-MG951768). Strains belonging to the Gram-positive Bacillus genera (42, 39 and 32% from battery 10-17, 10-22, and 5-27, respectively) were the most common isolated across the three oil wells (FIGS. 1A-C). A total of 42 strains recovered from oil battery 10-22 were distributed among six different genera with the highest relative abundance among isolates being Bacillus (11/42), Microbacterium (13/42) and Streptomyces (7/42) species (FIG. 1A). Fifty isolates were recovered from oil battery 5-27 and belonged to 10 different genera, with Bacillus isolates again having the highest relative abundance (15/50). This battery also had isolates of Arthrobacter (10/50), Pseudomonas (7/50), Curtobacterium (7/50) and Brevibacterium (3/50) that were retrieved only from this oil well (FIG. 1B). Lastly, there were 31 isolates representing seven different genera recovered from well 10-27, with isolates of Staphylococcus (11/31), Stenotrophomonas (3/31), Alcaligenes (1/31), Kineococcus 1(31) and Pantoea (1/31) associated exclusively with this well (FIG. 1C).

EXAMPLE 3: BIOSURFACTANT PRODUCTION

[0106] Thirty-four (34) isolates associated with Bacillus, Streptomyces, Microbacterium, Micrococcus, Rhodococcus, Pseudomonas, Arthrobacter and Staphylococcus genera retrieved from the three oil wells were identified as biosurfactant-producing bacteria using the oil—spreading and the drop collapse methods (Table IV). Isolates of Bacillus species showed the highest biosurfactant activities based on both tests. Strain OB9 isolated from oil well 10-22 and identified as B. methylotrophicus by whole genome sequencing (Jeukens et al., 2015, nucleotide sequence deposited at DDBJ/EMBUGenBank under accession number LGAU00000000) exhibited the highest biosurfactant activity followed by four strains of B. amyloliquifaciens (strains OB5, OB6, M30 and M09). Furthermore, these strains also tested positive for biosurfactant activity using the blood agar lysis method (a zone of 2.5 cm or greater), the CTAB method (a clearing zone of more than 1 mm), a significant grid using the microplate assay and in the emulsification assays (OD.sub.600 value of 1.0) (Data not shown).

EXAMPLE 4: ANTIMICROBIAL ACTIVITY OF B. METHYLOTROPHICUS OB9

[0107] B. methylotrophicus OB9 was effective against all tested bacteria and fungi with varying degrees of antimicrobial activity (Table V, below; FIG. 2). More specifically, live cultures of B. methylotrophicus OB9 inhibited the growth of 23 Salmonella serovars (environmental, clinical and foodborne isolates), 4 strains of E. coli, 10 environmentally isolated Enterobacteriaceae strains and an X. campestris pv. Vitians isolate (Table V, below, FIGS. 2B-D) in agar diffusion assays, as visualized by a clear zone around the B. methylotrophicus OB9 colony that developed over 24-48 h. The diameter of the inhibition zone ranged from 3-6 mm and with some E. coli and Salmonella serovars a clear zone with double rings was observed (Table V, below), indicating the potency of one or more antimicrobials. The greatest zones of inhibition (6 mm in diameter) in response to B. methylotrophicus OB9 were observed in trials with X. campestris pv. Vitians and Salmonella serovar I:Rough-O:e,h:e,n (FIGS. 2B and C). Other Salmonella serovars I:4,5,12:b:-,I:Rough-O:-:e,n,x, Hartford, and Heidelberg) were also highly sensitive to B. methylotrophicus OB9, exhibiting clearing zones of 5 mm.

[0108] Interestingly, the biofilm-forming phenotypes (i.e., rdar—denoting the presence of the extracellular polysaccharide, cellulose, and curli fimbriae; saw—denoting the absence of cellulose and curli; Table III, above) of the Salmonella strains did not affect the ability of B. methylotrophicus OB9 to elicit zones of clearing. Even all of the control S. enterica Typhimurium strains that express both cellulose and curli (UMR1), only cellulose (MAE14), only curli fimbriae (MAE299) or neither component (MAE775) had a measurable zone of clearing around the B. methylotrophicus OB9 colony on the plates. These results suggest that the antimicrobial activities of B. methylotrophicus OB9 are not significantly affected by the biofilm barrier that bacterial cells use to exclude other antimicrobial agents (including disinfectants and antibiotics).

[0109] The widespread effectiveness of B. methylotrophicus OB9 is further exemplified by its ability to also inhibit the growth of plant pathogenic fungi Rhizoctonia solani and Botrytis cinerea, as observed in the dual confrontation assays (Table V, below; FIG. 2A).

TABLE-US-00005 TABLE V Antagonistic activity of OB9 cultures against bacteria and fungi OB9 Live S. NO Strain ID Identity cells 1 UMR1 Salmonella typhimurium +++ 2 MAE14 S. typhimurium + 3 MAE299 S. typhimurium + 4 MAE775 S. typhimurium ++ 15 SC01 Serotype 1: 4, 5, 12: b: +++* 16 SC16 Serotype I: Rough-O: : e, n, x +++* 17 SC04 Serotype Braenderup ++ 18 SCS7 Serotype Typhimurium + 19 SC110 Serotype I: Rough-O: y: e, n, x ++ 20 SC12 Serotype I: Rough-O: e, h + 21 SC18 Serotype Hartford +++* 22 SCS2 Serotype: Rough-O: e, h: e, ++++ 23 WTCR5 Serotype 1: 6, 7: r + 24 WTCR6 Serotype Stanley + 25 WTCR9 Serotype InfaNtis ++ 26 WTCR30 Serotype- Schwarzengrund + 27 WTCR22 Serotype Thompson ++ 28 WTC27 serotype Heidleberg +++* 29 WTC28 Serotype Monschaui + 30 WTCT4 Serotype Heidleberg ++ 31 S. agona PARC#5 S. agona ++ 32 SL1 S. Newport ++ 33 SL2 S. Hartford ++ 34 B07.007 Xanthomonas hortorum ++++ 35 E3-6 Escherichia coli + 36 E10-6 E. coli ++ 37 E14-6 E. coli +++* 38 E15-6 E. coli + 39 AG3-114 Rhizoctonia solani +++  40 AG1-1(ROS-2A4) R. solani + 41 F014 Botrytis cinerea + Clearing zone of and above 3 mm is considered as positive; + clearing zone of 3 mm, ++ clearing zone of 4 mm, +++ 5 mm, ++++ 6 mm. ** Double ring of clearing zone.

EXAMPLE 5: FRACTIONATION OF BIOSURFACTANT FROM B. METHYLOTROPHICUS OB9

[0110] Biosurfactants were partially purified from culture filtrates of B. methylotrophicus OB9 grown in BHM broth enriched with oil. The purification procedure consisted of HCl precipitation, concentration of the precipitate by freeze-drying, dissolution in methanol-chloroform and analysis by TLC (FIG. 3A). Fractionation of cell free supernatant (CFS) yielded 4 fractions (1-4), while the acid precipitate fraction (APF) separated into 5 parts. Between the CFS and APF samples, fractions 2 and 3 from the respective samples had identical Rf values (0.68 and 0.23) (FIG. 3A).

EXAMPLE 6: BIOSURFACTANT AND ANTIMICROBIAL ACTIVITY OF THE ACID PRECIPITATE FRACTION (APF) OF B. METHYLOTROPHICUS STRAIN OB9

[0111] Only APF fractions (1-5) were assayed for biosurfactant and antimicrobial activities due to their improved purity and concentration relative to the CFS samples. All of the 5 TLC purified fractions of APF showed biosurfactant activity in the drop-collapse and oil-spreading assays (FIGS. 3B-3C). Fractions 3 and 5 had strong antimicrobial activities in diffusion agar plates against 13 test bacteria. This test panel included six Salmonella enterica serovars originating from the environment (SCS2), human fecal matter (SL1), or contaminated fresh produce (S. agoni Parc#5), as well as strains of E. coli and X. campestris (Data not shown) (a plant pathogenic bacterium) (Table VI, below; FIGS. 4A-D). Additionally, the APF fractions were moderately effective against two fungal plant pathogens (R. solani and B. cinerea) (Table VI, below; FIG. 4E); thereby indicating that these fractions have widespread microbial bioactivity. Furthermore, the size of the inhibition zones produced by the APF fractions (especially fraction 5) was comparable to that produced by the positive controls (Control (+ve), bleach (FIG. 4A) or common organic acids (lactic and acetic acid controls; FIGS. 4B-D) used as disinfectants and antimicrobials. Interestingly, the crude APF fraction (i.e., prior to TLC separation into fractions 3 (F3) and 5 (F5)) exhibited weak antimicrobial activity against the 13 bacteria and only one of the fungi (Table VI, below). Thus, isolation and partial enrichment of these fractions has increased their relative concentrations and/or efficacy.

TABLE-US-00006 TABLE VI Microbial activity of the B. methylotrophicus OB9 fractions, organic acids and bleach against various pathogenic bacteria and fungal strains TLC Fractions Organic Acids.sup.a Bleach NO Strain ID Identity Live cells APF F3 F5 AA LA FA CA 1.3% 1 UMR1 Salmonella enterica Typhimurium +++ + ++ +++ ++ + +++ + ++ 2 MAE14 S. enterica Typhimurium + + ++ ++ ++ ++ +++ + ++ 3 MAE299 S. enterica Typhimurium + + +++ ++ ++ + +++ + ++ 4 MAE775 S. enterica Typhimurium ++ + ++ ++ +++ + +++ + ++ 5 SCS2 S. enterica I: Rough-O: e, h: e, n ++++ + ++ ++ ++ + +++ + ++ 6 PARC#5 S. enterica Agona ++ + + ++ ++ + +++ + ++ 7 SL1 S. enterica Newport ++ + ++ ++ ++ + +++ + ++ 8 SL2 S. enterica Hartford ++ + ++ ++ ++ + +++ + ++ 9 B07.007 Xanthomonas campestris ++++ + ++ +++ +++ ++ +++ ++ ++ 10 E3-6 Escherichia coli + + ++ ++ ++ + +++ + ++ 11 E10-6 E. coli ++ + ++ ++ ++ + +++ + ++ 12 E14-6 E. coli .sup. +++.sup.b + ++ ++ ++ + +++ + ++ 13 E15-6 E. coli + + ++ ++ ++ + +++ + ++ 14 AG3 (114) Rhizoctonia solani +++ + + ++ ++ + +++ + ++ 15 AG1-1A (ROS-2A) R. solani + − + + ++ + +++ + ++ 16 F014 Botrytis cinerea + − + + ++ + +++ + ++ .sup.aVarious organic acids (1%) tested as controls: AA, Acetic acid; LA, lactic acid; FA, formic acid; CA, citric acid. .sup.bDouble ring of clearing zone. (+) clearing zone of 3 mm; (++) clearing zone of 4 mm; clearing zone of 5 mm (+++); clearing zone of 6 mm. (++++)

EXAMPLE 7: SUPPRESSION OF SALMONELLA AND XANTHOMONAS GROWTH DURING CO-CULTURE WITH B. METHYLOTROPHICUS OB9

[0112] Salmonella cell numbers in liquid co-cultures with B. methylotrophicus OB9 significantly (P<0.05) decreased at 3 h (31-fold) and 6 h (45-fold) after incubation compared to growth controls (FIG. 5A). Similarly, X. campestris was 5 recovered 3 h and 6 h after incubation in co-cultures, with significant decreases of 22- and 47-fold in cell number, respectively (FIG. 5C). Furthermore, neither S. enterica Newport nor X. campestris were retrieved from co-cultures after 12 h or more of incubation (FIGS. 5A and C), while B. methylotrophicus OB9 continued to grow at a comparable rate to cultures of B. methylotrophicus OB9 alone (FIGS. 5B and D). To rule out the possibility of nutrient competition as a source of the antagonistic behaviour, media was replaced every 10 h, but this did not affect results.

EXAMPLE 8: RECOLONIZATION, INTERNALIZATION, AND DETECTION OF BACTERIAL ISOLATES IN PLANT TISSUES

[0113] The surface-sterilization method combined with the imprint technique ensured that the endophytic colonization numbers reflected only the cells within the interior of the plant tissues (i.e., bacterized), as non-colonized plants did not yield culturable bacterial colonies (data not shown). Subsequent isolation and quantification of B. methylotrophicus (OB9) following surface sterilization demonstrated that the strain can travel from the roots to the stems and leaves and develop sustained endophytic populations in plant tissues of tomato (log.sub.10 7) and lettuce (log.sub.10 8) grown under gnotobiotic conditions even after the plants were challenged with Salmonella and Xanthomonas strains (FIGS. 6A-D and 7A-B).

EXAMPLE 9: IMPACT OF PLANTS BACTERIZED WITH B. METHYLOTROPHICUS OB9 ON THE GROWTH OF SALMONELLA AND XANTHOMONAS

[0114] Tomato and lettuce leaves of B. methylotrophicus OB9 bacterized plants were detached and placed separately into petri plates lined with sterile filter paper that was moistened with sterile distilled water. An aliquot (100 μL) of each of Salmonella enterica Newport SL1 and X. campestris B07.007 inoculum (10.sup.6 cells mL.sup.−1) was spread with a disposable spreader (Fischer Scientific Ltd) onto the surface of a tomato or lettuce leaf (S. enterica Newport SL1 and X. campestris B07.007, respectively). Non-bacterized leaves of tomato and lettuce were inoculated in the same manner and served as negative controls. All plates were sealed with parafilm and incubated at 22° C. Recovery of bacterial strains was determined by cell count after 72 h. Leaf tissue (100 mg) from infected and bacterized or non-bacterized plants was macerated in distilled water and serially diluted (10.sup.−1 to 10.sup.−7) and aliquots from each dilution were plated on LBA plates and bacterial cell counts were estimated and reported as log.sub.10 mL.sup.−1. Detection of Salmonella on tomato leaves was confirmed by PCR with Salmonella specific primers ST11 (5′-GC CAA CCA TTG CTA AAT TGG CGC A-3′) (SEQ ID NO: 116) and ST15 (5′-GGT AGA AAT TCC CAG CGG GTA CTG-3′) (SEQ ID NO: 117) using an annealing temperature of 57° C. with PCR conditions described previously (Soumet et al., 1999). Detection of X. Campestris on lettuce leaves was confirmed using primers XcpM1 (5′-ACGCGCTACCAAAAGGCAAAGAG-3′) (SEQ ID NO: 118) and XcpM2 (5′-GATCTGCGGTTGTCCTGAAGATTGG-3′)(SEQ ID NO: 119) in conventional PCR assays (Sulzinski et al., 1996).

[0115] Leaves of B. methylotrophicus (OB9) bacterized tomato and lettuce plants challenged with Salmonella and Xanthomonas appeared healthy compared to challenged non-bacterized plants (FIGS. 6A-D). There was a significant (P<0.05) reduction of Salmonella cells (44% or 4.4-fold decrease) recovered from bacterized tomato leaves after 72 h (FIGS. 6A-B and 7A) compared to challenged non-bacterized leaves. In the case of Xanthomonas, there was no growth as reflected by complete absence of cells from bacterized lettuce tissues after 72 h (FIGS. 6B-C and 7B). Amplification of genomic DNA extracted from bacterized leaf samples using designed B. methylotrophicus OB9 specific primers gave the expected band size of 565 bp in leaf and root tissue samples (data not shown). Similarly, amplification of Salmonella from bacterized plants gave the expected band size of 429 bp, so the presence/absence of these bacteria was confirmed by this secondary method (data not shown). PCR amplification of Xanthomonas DNA was not successful using the XcpM 1/XcpM2 primers so this organism could not be detected in coated and challenged lettuce leaves by this secondary method.

EXAMPLE 10: DIRECT INTERACTION OF B. METHYLOTROPHICUS OB9 WITH SALMONELLA ENTERICA NEWPORT SL1 OR WITH X. CAMPESTRIS B07.007 ON LEAF SURFACES

[0116] Tomato and lettuce leaves were submerged in 100 mL (10.sup.6 cells mL.sup.−1) of B. methylotrophicus OB9 in a petri plate for 30 s and then left for 2 h. Aliquots (100 μL) of each of Salmonella and Xanthomonas strains (10.sup.6 cells mL.sup.−1) were spread on the leaves, and incubated in petri plates at 22° C. Inoculums of Salmonella or Xanthomonas strains were also spread on non-inoculated tomato or lettuce leaves and served as experimental controls. After 72 h of incubation, recovery of bacterial cells from the leaves was determined by tissue maceration and cell count determination as described above.

[0117] In this experiment, where tomato and lettuce leaves were coated with B. methylotrophicus OB9 (as opposed to bacterized as in Example 9) and challenged with Salmonella and Xanthomonas, similar trends were noted to the bacterized experiment. Recovery of Salmonella cell-numbers from these leaves was significantly decreased by 54% (5.4-fold decrease) compared to leaves treated with Salmonella alone (FIG. 7C). As in the bacterized experiment, Xanthomonas was not recovered in the B. methylotrophicus OB9 coating experiments either (FIG. 7D).

[0118] The scope of the claims should not be limited by the embodiments set forth in the examples but should be given the broadest interpretation consistent with the description as a whole.

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