CHARACTERIZATION OF RHODOSPIRILLUM-RUBRUM ST2 - A NEW TN5-INDUCED CAROTENOID-LESS MUTANT FOR FUNCTIONAL-STUDIES

Random Tn5 mutagenesis of the purple non-sulphur bacterium Rhodospiril lum rubrum S1 allowed the isolation of a photosynthetically competent blue-green mutant, R. rubrum ST2. Southern hybridization showed that t he Tn5 element was present as a single copy within the chromosome and distant from the puf operon. Phenotypic characterization of the mutant showed that the spectral characteristics of the photosynthetic comple xes and water-soluble cytochromes were identical to those of the commo nly used mutant R, rubrum G9. The protein SDS-PAGE profiles of the wat er-soluble and membrane fractions were essentially identical for both R. rubrum G9 and ST2. R. rubrum ST2 is suggested to be useful for stru ctural and functional studies of bacterial photosynthesis.