ABSTRACT

In the bacterial world, the greatest capacity for adaptation to a range of nutritional conditions is shown by purple photosynthetic bacteria and hydrogen bacteria. Among the former, the nonsulfur purple bacteria (Rhodospirillaceae) are of particular interest because of their remarkable metabolic versatility. Cyanobacteria therefore photosynthetic reducing equivalents are derived from water and are not dependent on the availability of reduced metabolites. Many of the oxidases detected in facultative photosynthetic bacteria are able to react with carbon monoxide, and furthermore the respiratory electron transport system is sensitive to cyanide. In addition to the high mid-point potential b- and aa3-type components associated with oxidase activities, many other electron transport carriers have been identified in membranes from nonsulfur purple bacteria. Regarding c-type cytochromes, their presence in nonsulfur purple bacteria seems to be mainly related to only one component, cytochrome c2, which defines a characteristic class of electron transport proteins.