title: Light as an energy source in continuous cultures of bacteriorhodopsin-containing halobacteria.
abstract: The role of light as an energy source for slightly aereated cultures of halobacteria was studied, using continuous cultures with low nutrient concentrations and a low oxygen supply. A series of experiments were carried out with non-illuminated and differently illuminated cultures and with different oxygen transfer rates. Under low oxygen availability, light proved to be a decisively important energy source that allowed the populations to reach higher growth rates and much higher population densities. Oxygen influenced the growth over only a minimal level, below which neither the illuminated nor the dark cultures were affected by the oxygen transfer rate. From these results, it appears that the bacteriorhodopsin-mediated energy supply could have a very important role for the ecology of halobacteria in their microaerophilic habitats. In the illuminated cultures, cells that originated purple colonies on plates appeared. These cells, which could be bacteriorhodopsin-constitutive mutants, are now being studied.
authors.affiliation: Department of Microbiology, Faculty of Pharmacy, University of Sevilla, Sevilla, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Rodriguez-Valera
authors.forename: J J
authors.initials: JJ
authors.lastname: Nieto
authors.forename: F
authors.initials: F
authors.lastname: Ruiz-Berraquero