Membrane Rigidity and Phosphatidic Acid (PtdOH) Signal: Two Important Events in Acinetobacter guillouiae SFC 500‐1A Exposed to Chromium(VI) and Phenol

Abstract

The remodeling of membrane lipids is a mechanism that allows microorganisms to survive in unfavorable environments such as industrial effluents, which often contain inorganic and organic pollutants, like chromium and phenol. In the present work, we evaluated the effect of Cr(VI) and phenol on the membrane of Acinetobacter guillouiae SFC 500‐1A, a bacterial strain isolated from tannery sediments where such pollutants can be found. The presence of lipid kinases and phospholipases and the changes in their activities under exposure to these pollutants were determined. Cr(VI) and Cr(VI) + phenol caused the membrane to become more rigid for up to 16 h after exposure. This could be due to an increase in cardiolipin (Ptd2Gro) and a decrease in phosphatidylethanolamine (PtdEtn), which are indicative of more order and rigidity in the membrane. Increased phospholipase A activity (PLA, EC 3.1.1.4) could be responsible for the decrease in PtdEtn levels. Moreover, our results indicate that Cr(VI) and Cr(VI) + phenol trigger the phosphatidic acid (PtdOH) signal. The finding of significantly increased phosphatidylinositol‐4‐phosphate (PtdIns‐4‐P) levels means this is likely achieved via PtdIns‐PLC/DGK. This report provides the first evidence that A. guillouiae SFC 500‐1A is able to sense Cr(VI) and phenol, transduce this signal through changes in the physical state of the membrane, and trigger lipid‐signaling events.

Genetic evidence for functional diversification of gram-negative intermembrane phospholipid transporters

“…Δ yhdP Δ tamB strains have much greater OM permeability (30) than the Δ yhdP or Δ yhdP Δ fadR strains. Third, CL has been shown to have a normalizing, bidirectional, and leaflet-specific effect on lipid packing order (9, 73-76) and membrane fluidity (77-80) opposite of or similar to that of cholesterol, respectively, and so is unlikely to contribute to a phenotype dependent solely on OM membrane fluidity. Thus, the cold sensitivity phenotype correlates with the impairment of phospholipid trafficking and the likely imbalance of phospholipids between the IM and OM and not with the permeability phenotypes of the OM.…”

Genetic evidence for functional diversification of gram-negative intermembrane phospholipid transporters

“…ΔyhdP ΔtamB strains have much greater OM permeability [30] than the ΔyhdP or ΔyhdP ΔfadR strains. Third, CL has been shown to have a normalizing, bidirectional, and leaflet-specific effect on lipid packing order [9,[74][75][76][77] and membrane fluidity [78][79][80][81] opposite of or similar to that of cholesterol, respectively, and so is unlikely to contribute to a phenotype dependent solely on OM membrane fluidity. Thus, the cold sensitivity phenotype correlates with the impairment of phospholipid trafficking and the likely imbalance of phospholipids between the IM and OM and not with the permeability phenotypes of the OM.…”

Galleria mellonella as a Good Model to Study Acinetobacter baumannii Pathogenesis

“…Both cut between the phosphorylated and the polar head groups. In addition, PLs can disturb the host-immune response by generating second messengers such as phosphatidic acid, which can also promote the pathogenesis [104]. Kareem et al have tested 30 A. baumannii strains collected from hospitalized patients with G. mellonella killing assays [42].…”