Manganous ions suppress photosynthesis gene expression in Rhodobacter sphaeroides.
The effect of manganous ions [Mn(II)] and ferrous ions [Fe(II)] on expression of photosynthesis genes in Rhodobacter sphaeroides was investigated. The presence of Mn(II) during phototrophic (anaerobic) and chemotrophic (aerobic) growth of R. sphaeroides caused a decrease in the amount of bacteriochlorophyll and carotenoid pigments which were synthesized and this was associated mainly with a decrease in the level of light-harvesting complex II. Mn(II) was shown to cause a decrease in expression of the puc operon, which encodes the polypeptides of light-harvesting complex II. Expression of the puc operon is controlled by the central repressor of photosynthesis gene expression, PpsR. In a ppsR mutant there was no effect of Mn(II) on photosynthesis gene expression. It is concluded that Mn(II) may act as a corepressor in the action of PpsR or act via an as yet uncharacterized protein that interacts with PpsR. In contrast to the effects of Mn(II), Fe(II) was required for high levels of photosynthesis gene expression. This requirement for Fe(II) was shown to be related to the regulation of hemA, a gene under the control of the transcriptional regulator, FnrL. Mn(II) did not affect FnrL-dependent gene expression.
Department of Microbiology, The University of QueenslandBrisbane 4072Australia.
Irene M
IM
Horne
Department of Microbiology, The University of QueenslandBrisbane 4072Australia.
John M
JM
Pemberton
Department of Microbiology, The University of QueenslandBrisbane 4072Australia.
Alastair G
AG
McEwan
D002413:Cations, Divalent / Q000494:pharmacology; D005296:Ferrous Compounds / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial / Q000187:drug effects*; D045342:Light-Harvesting Protein Complexes; D008345:Manganese / Q000494:pharmacology*; D009532:Nickel / Q000494:pharmacology; D010788:Photosynthesis / Q000187:drug effects / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D012242:Rhodobacter sphaeroides / Q000187:drug effects / Q000235:genetics*
D002413:Cations, Divalent; D005296:Ferrous Compounds; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D008345:Manganese; D009532:Nickel