Isolation and characterization of a glycerol auxotroph of Rhodopseudomonas capsulata: effect of lipid synthesis on the synthesis of photosynthetic pigments

Exogenously supplied long-chain fatty acids have been shown to markedly alleviate the inhibition of phototrophic growth of cultures of Rhodopseudomonas sphaeroides caused by the antibiotic cerulenin. Monounsaturated and polyunsaturated C18 fatty acids were most effective in relieving growth inhibition mediated by cerulenin. Medium supplementation with saturated fatty acids (C14 to C18) failed to influence the inhibitory effect of cerulenin. The addition of mixtures of unsaturated and saturated fatty acids to the growth medium did not enhance the growth of cerulenin-inhibited cultures above that obtained with individual unsaturated fatty acids as supplements. Resolution and fatty acid analysis of the extractable lipids of R. sphaeroides revealed that exogenously supplied fatty acids were directly incorporated into cellular phospholipids. Cells treated with cerulenin displayed an enrichment in their percentage of total saturated fatty acids irrespective of the presence of exogenous fatty acids. Cerulenin produced comparable inhibitions of the rates of both fatty acid and phospholipid synthesis and was further found to preferentially inhibit unsaturated fatty acid synthesis. 782 on July 31, 2020 by guest

Section: Discussionmentioning

confidence: 99%

Long-chain fatty acid assimilation By rhodopseudomonas sphaeroides

Campbell¹,

Lueking²

1983

“…One approach to the study of membrane assembly involves uncoupling protein and phos-pholipid syntheses. This has been accomplished in bacterial systems by depriving glycerol-requiring auxotrophs of this polyol (2,28,35,37,47). Under such circumstances, phospholipid is no longer synthesized, and it is possible to study the incorporation of membrane proteins independent of concomitant phospholipid insertion (34,36,37).…”

Section: Synthesesmentioning

confidence: 99%

“…Under such circumstances, phospholipid is no longer synthesized, and it is possible to study the incorporation of membrane proteins independent of concomitant phospholipid insertion (34,36,37). During cessation of phospholipid synthesis in a glycerol auxotroph of the related photosynthetic bacterium Rhodopseudomonas capsulata, protein synthesis continued for one doubling, whereas that of bacteriochlorophyll a (Behl) and carotenoids was markedly inhibited (28). An association between the synthesis of phospholipid and photosynthetic pigments was demonstrated previously during chromatophore membrane induction in R. sphaeroides (30).…”

Section: Synthesesmentioning

confidence: 99%

Membranes of Rhodopseudomonas sphaeroides: effect of cerulenin on assembly of chromatophore membrane

Broglie¹,

Niederman²

1979

The effects of cerulenin were investigated in Rhodopseudomonas sphaeroides to elucidate further the mechanisms controlling the assembly of the chromatophore membrane. When this potent inhibitor of fatty acid biosynthesis was added to photosynthetically grown cultures, there was an immediate cessation of phospholipid, bacteriochlorophyll a, carotenoid, and ubiquinone formation. Concurrently, there was also a marked decrease in the rate of incorporation of protein into the chromatophore membrane. In contrast, only a small decrease in the rate of soluble and cell envelope protein synthesis was observed and, in chemotrophically grown cells, protein continued to be incorporated into both the cytoplasmic and outer membranes. The removal of delta-aminolaevulinate from mutant H-5 of R. sphaeroides, which requires this porphyrin precursor, was reexamined to determine whether cerulenin-induced cessation of chromatophore protein incorporation was due solely to blocked bacteriochlorophyll a synthesis. In the deprived H-5 cells, inhibition of [35S]methionine incorporation into chromatophores was confined mainly to apoproteins of bacteriochlorophyll a complexes. Other minor chromatophore proteins continued to be inserted to a greater extent than in cerulenin-treated wild type where phospholipid synthesis has also ceased. These results indicated that the assembly of the chromatophore membrane is under strict regulatory control involving concomitant phospholipid, pigment, and protein syntheses.

“…The events that follow appear to be directly or indirectly caused by the lack of ongoing phospholipid synthesis and not by any consequent abnormality in the composition of the phospholipids. In general, phospholipid turnover in this organism is very slow, approximately 10% per generation (6), compared to approximately 40% in Escherichia coli (31) and 60% in Rhodopseudomonas capsulata (23).…”

Section: Discussionmentioning

confidence: 99%

Caulobacter cresentus mutant defective in membrane phospholipid synthesis

Contreras¹,

Bender²,

Mansour³

et al. 1979

To study the relationship between phospholipid synthesis and organelle biogenesis in the dimorphic bacterium Caulobacter crescentus, auxotrophs have been isolated which require exogenous glycerol or glycerol 3-phosphate for growth when glucose is used as the carbon source. Upon glycerol deprivation, net phospholipid synthesis ceased immediately in a glycerol 3-phosphate auxotroph which was shown to have levels of biosynthetic sn-glycerol 3-phosphate dehydrogenase (E.C. 1.1.1.8) activity 10 times lower than that of the wild type. In the absence of glycerol, the optical density of the culture continued to increase for the equivalent of one generation, although the cells did not divide. After the equivalent of one generation time, rapid cell death occurred. Cell death also occurred when phospholipid synthesis was inhibited by cerulenin. Although ribonucleic acid and protein syntheses continued at a reduced rate for the equivalent of one generation in mutant strains, a substantial decrease in the rate of deoxyribonucleic acid synthesis occurred immediately upon glycerol deprivation. Revertant strains had wild-type levels of glycerol 3-phosphate dehydrogenase activity and normal rates of phospholipid and macromolecular synthesis.