Lipid Lysyl-Phosphatidylglycerol Is Present in Membranes of Rhizobium tropici CIAT899 and Confers Increased Resistance to Polymyxin B Under Acidic Growth Conditions

• Published in: Molecular plant-microbe interactions Vol. 20; no. 11; pp. 1421 - 1430
• Main Authors: Sohlenkamp, C, Galindo-Lagunas, K.A, Guan, Z, Vinuesa, P, Robinson, S, Thomas-Oates, J, Raetz, C.R.H, Geiger, O
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01.11.2007; The American Phytopathological Society
• Subjects: Agronomy. Soil science and plant productions; Bacillus subtilis - genetics; Bacillus subtilis - metabolism; Bacterial plant pathogens; Biological and medical sciences; Cell Membrane - chemistry; cell membranes; Cloning, Molecular; culture media; drug resistance; Drug Resistance, Bacterial; Economic plant physiology; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation, Bacterial; Genes, Bacterial; genome; Gram-negative bacteria; Hydrogen-Ion Concentration; Lysine - analysis; membrane lipids; microbial genetics; molecular sequence data; mutants; nucleotide sequences; Operon; phosphatidylglycerols; Phosphatidylglycerols - analysis; Phytopathology. Animal pests. Plant and forest protection; polymyxin B; Polymyxin B - pharmacology; Rhizobium tropici; Rhizobium tropici - chemistry; Rhizobium tropici - drug effects; Sinorhizobium medicae; Sinorhizobium meliloti; Sinorhizobium meliloti - genetics; Sinorhizobium meliloti - metabolism; Staphylococcus aureus; Staphylococcus aureus - genetics; Staphylococcus aureus - metabolism; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Yeast; Microbiology; Peptides; Escherichia coli; Rhizobium tropici; Biosynthesis; Symbiont; Strain; Resistance; Plant; Gene; Gram positive bacteria; Bacteria; Micrococcales; Micrococcaceae; Complementation; Rhizobiaceae; Mutation; Genome; Sinorhizobium meliloti; Staphylococcus aureus; Enterobacteriaceae; Gram negative bacteria
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-20-11-1421

Lysyl-phosphatidylglycerol (LPG) is a well-known membrane lipid in several gram-positive bacteria but is almost unheard of in gram-negative bacteria. In Staphylococcus aureus, the gene product of mprF is responsible for LPG formation. Low pH-inducible genes, termed lpiA, have been identified in the gram-negative α-proteobacteria Rhizobium tropici and Sinorhizobium medicae in screens for acid-sensitive mutants and they encode homologs of MprF. An analysis of the sequenced bacterial genomes reveals that genes coding for homologs of MprF from S. aureus are present in several classes of organisms throughout the bacterial kingdom. In this study, we show that the expression of lpiA from R. tropici in the heterologous hosts Escherichia coli and Sinorhizobium meliloti causes formation of LPG. A wild-type strain of R. tropici forms LPG (about 1% of the total lipids) when the cells are grown in minimal medium at pH 4.5 but not when grown in minimal medium at neutral pH or in complex tryptone yeast (TY) medium at either pH. LPG biosynthesis does not occur when lpiA is deleted and is restored upon complementation of lpiA-deficient mutants with a functional copy of the lpiA gene. When grown in the low-pH medium, lpiA-deficient rhizobial mutants are over four times more susceptible to the cationic peptide polymyxin B than the wild type.