The regulator gene phoB mediates phosphate stress‐controlled synthesis of the membrane lipid diacylglyceryl‐N,N,N‐trimethylhomoserine in Rhizobium (Sinorhizobium) meliloti

• Published in: Molecular microbiology Vol. 32; no. 1; pp. 63 - 73
• Main Authors: Geiger, Otto, Röhrs, Viola, Weissenmayer, Barbara, Finan, Turlough M., Thomas‐Oates, Jane E.
• Format: Journal Article
• Language: English
• Published: Oxford BSL Blackwell Science Ltd 01.04.1999; Blackwell Publishing Ltd
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - physiology; Cell Culture Techniques - methods; Chromatography, Thin Layer; Escherichia coli Proteins; Genes, Regulator; Mass Spectrometry; Membrane Lipids - biosynthesis; Membrane Lipids - metabolism; Membrane Transport Proteins; Phosphates - physiology; Plasmids; Rhizobium meliloti; Sinorhizobium meliloti; Sinorhizobium meliloti - physiology; Transcription Factors; Triglycerides - metabolism
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1046/j.1365-2958.1999.01325.x

Bacteria react to phosphate starvation by activating genes involved in the transport and assimilation of phosphate as well as other phosphorous compounds. Some soil bacteria have evolved an additional mechanism for saving phosphorus. Under phosphate‐limiting conditions, they replace their membrane phospholipids by lipids not containing phosphorus. Here, we show that the membrane lipid pattern of the free‐living microsymbiotic bacterium Rhizobium (Sinorhizobium) meliloti is altered at low phosphate concentrations. When phosphate is growth limiting, an increase in sulpholipids, ornithine lipids and the de novo synthesis of diacylglyceryl trimethylhomoserine (DGTS) lipids is observed. Rhizobium meliloti phoCDET mutants, deficient in phosphate uptake, synthesize DGTS constitutively at low or high medium phosphate concentrations, suggesting that reduced transport of phosphorus sources to the cytoplasm causes induction of DGTS biosynthesis. Rhizobium meliloti phoU or phoB mutants are unable to form DGTS at low or high phosphate concentrations. However, the functional complementation of phoU or phoB mutants with the phoB gene demonstrates that, of the two genes, only intact phoB is required for the biosynthesis of the membrane lipid DGTS.