Adaptation of Pseudomonas aeruginosa to various conditions includes tRNA‐dependent formation of alanyl‐phosphatidylglycerol

Abstract

SummaryThe opportunistic bacterium Pseudomonas aeruginosa synthesizes significant amounts of an additional phospholipid, identified as 2Ј alanylphosphatidylglycerol (A-PG), when exposed to acidic growth conditions. At pH 5.3 A-PG contributed up to 6% to the overall lipid content of the bacterium. Sequence analysis of P. aeruginosa revealed open reading frame PA0920 showing 34% sequence identity to a protein from Staphylococcus aureus involved in tRNA-dependent formation of lysylphosphatidylglycerol. The P. aeruginosa deletion mutant DPA0920 failed to synthesize A-PG. Heterologous overproduction of PA0920 in Escherichia coli resulted in the formation of significant amounts of A-PG, otherwise not synthesized by E. coli. Consequently, the protein encoded by PA0920 was named A-PG synthase. The enzyme was identified as an integral component of the inner membrane. The protein was partially purified by detergent solubilization and subjected to an in vitro activity assay. tRNA

Deciphering the tRNA-dependent lipid aminoacylation systems in bacteria: Novel components and structural advances

“…The effects of aa-PG on antibiotic resistance have been investigated in several important human pathogens such as S. aureus (for review see [4]), L. monocytogenes , 53 B. anthracis , 58 P. aeruginosa , 24,59 M. tuberculosis , 29,60 Enterococcus species, 35,36,61 and B. subtilis 62,63 (for review see [1]). aa-PGs in these organisms primarily enhance bacterial resistance to positively charged compounds targeting the membrane (such as CAMPs) and last resort lipopetides like daptomycin.…”

“…66 Similarly, resistance phenotypes against β-lactams were observed in P. aeruginosa , which produces Ala-PG. 59 In M. tuberculosis , Lys-PG was shown to increase resistance to vancomycin. 29 β-lactams and vancomycin are antibiotics that do not interact with the cytoplasmic membrane; both compounds target distinct components of the peptidoglycan synthesis machinery inside the periplasm (i.e., penicillin binding proteins and peptidoglycan connecting pentapeptides, respectively).…”

“…For instance, Ala-PG found in the outer membrane of the Gram-negative bacterium P. aeruginosa may modulate the activity of porins in the outer membrane that are necessary for β-lactams to reach their periplasmic targets. 59 Lys-PG synthesis in S. aureus on the other hand might modulate the activity of proteins involved in peptidoglycan synthesis, which would indirectly affect resistance to β-lactams and vancomycin. These hypotheses are supported by several studies that demonstrated that the lack of aa-PG in the membranes of S. aureus and L. monocytogenes induces significant changes in the membrane proteome and its function.…”

“…55,93,94,96 Because aa-PG does not provide any apparent tolerance to acidic conditions in E. faecium , it was recently proposed that lipid aminoacylation confers tolerance to inhibitors that are produced during exposure to acidic conditions, rather than to low pH levels themselves. For instance, aa-PGs enhance resistance of P. aeruginosa and E. faecium to lactic acid, 35,59 a toxic osmolyte known to diffuse passively through the cytoplasmic membrane of bacteria. 97 …”

Profiling and tandem mass spectrometry analysis of aminoacylated phospholipids in Bacillus subtilis

“…L-alanyl-PG has been found to be abundant in Gram-negative Pseudonomas aeruginosa 25 , which has a MprF homolog specific for L-analyl-tRNA substrate 10 . D-alanyl- and L-lysyl-cardiolipin (CL) have also been separated from Vagococcus fluvialis 26, 27 .…”