23S rRNA processing in Rhodobacter capsulatus is not involved in the oxygen-regulated formation of the bacterial photosynthetic apparatus

Abstract

The chemical mutant strain Fm65 differs from wild-type strains of Rhodobacter capsulatus in several respects: (a) Fm65 does not form photosynthetic complexes because it does not synthesize bacteriochlorophyll; (b) the level of puf mRNA encoding pigment binding proteins increases little after reduction of oxygen; (c) Fm65 does not process 23S rRNA into 14S and 16S rRNA species, and as a consequence of altered rRNA processing, has lower growth rates. Here we show that transfer of wild-type bchBN and bchF genes into Fm65 restores normal oxygen regulation of the formation of photosynthetic complexes, but not rRNA processing. We conclude that the processing of 23S rRNA to 16S and 14S rRNA species in wild-type strains is not involved in the regulation of the photosynthetic apparatus formation. Abnormal oxygen regulation of puf transcription in strain Fm65 could be attributed to the defect in bacteriochlorophyll synthesis, suggesting that porphyrins are directly or indirectly involved in oxygen regulation of the synthesis of pigment binding proteins.