title: Electrical spiking in Escherichia coli probed with a fluorescent voltage-indicating protein.
abstract: Bacteria have many voltage- and ligand-gated ion channels, and population-level measurements indicate that membrane potential is important for bacterial survival. However, it has not been possible to probe voltage dynamics in an intact bacterium. Here we developed a method to reveal electrical spiking in Escherichia coli. To probe bacterial membrane potential, we engineered a voltage-sensitive fluorescent protein based on green-absorbing proteorhodopsin. Expression of the proteorhodopsin optical proton sensor (PROPS) in E. coli revealed electrical spiking at up to 1 hertz. Spiking was sensitive to chemical and physical perturbations and coincided with rapid efflux of a small-molecule fluorophore, suggesting that bacterial efflux machinery may be electrically regulated.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Joel M
authors.initials: JM
authors.lastname: Kralj
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Hochbaum
authors.forename: Adam D
authors.initials: AD
authors.lastname: Douglass
authors.forename: Adam E
authors.initials: AE
authors.lastname: Cohen
mesh_terms: D000200:Action Potentials; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D005453:Fluorescence; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000378:metabolism; D017136:Ion Transport; D008027:Light; D008564:Membrane Potentials; D011522:Protons; D012235:Rhodamines / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025604:Rhodopsins, Microbial; D013050:Spectrometry, Fluorescence; D013312:Stress, Physiological
chemical_list: D005456:Fluorescent Dyes; D007473:Ion Channels; D011522:Protons; D012235:Rhodamines; D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; C401833:tetramethylrhodamine methyl ester; D012243:Rhodopsin