The present invention is directed generally to eukaryotic cells comprising single-celled organisms that are introduced into the eukaryotic cell through human intervention and which transfer to daughter cells of the eukaryotic cell through at least five cell divisions, and methods of introducing such single-celled organisms into eukaryotic cells. The invention also provides methods of using such eukaryotic cells. The invention further provides single-celled organisms that introduce a phenotype to eukaryotic cells that is maintained in daughter cells. The invention additionally provides eukaryotic cells containing magnetotactic bacteria.

There are provided peptide tags derived from bacteriophytochrome (BphP) that is photoreceptor protein of Deinococcus <i/> radiodurans, an antibody capable of specifically recognizing the peptide tags, hybridoma cell lines capable of producing the antibody, and uses thereof. The novel peptide tag has advantages in that it has a short length and can remove a non-specific reaction of the conventional c-myc tag and FLAG tag. Therefore, in the case of using the novel peptide tag and antibody thereto, the fusion protein expressed in a recombinant cell can be very effectively detected or purified. In addition, an epitope tagging system including the novel peptide tag and antibody thereto can be applied in various fields such as a determination of an intracellular site, a confirmation of functionality, detection and purification of specific protein, and researches on interaction between proteins.

Described herein are novel fluorescent sensors for Diacyl Glycerol (DAG) and hosphatidylinositol 4,5-bisphosphate (PIP2) that are based on circularly permuted fluorescent proteins. These sensors use less visible spectrum than FRET-based sensors, produce robust changes in fluorescence, and can be combined with one another, or with other sensors, in a multiplex assay on standard fluorescent plate readers or live cell imaging systems.