The eubacterium Ectothiorhodospira halophila is negatively phototactic, with a wavelength dependence that fits the absorption spectrum of the photoa

The motile, alkalophilic and extremely halophilic purple sulfur bacterium Ectothiorhodospira halophila is positively photophobotactic. In a study, it was demonstrated that E. halophila is also negatively phototactic. The wavelength dependence of a negative photoresponse was determined with narrow band pass interference filters, and it showed similarity to the absorption spectrum of the photoactive yellow protein from E. halophila.