Phospholipase A1 Modulates the Cell Envelope Phospholipid Content of Brucella melitensis, Contributing to Polymyxin Resistance and Pathogenicity

Abstract

A subset of bacterial pathogens, including the zoonotic Brucella species, are highly resistant against polymyxin antibiotics. Bacterial polymyxin resistance has been attributed primarily to the modification of lipopolysaccharide; however, it is unknown what additional mechanisms mediate high-level resistance against this class of drugs. This work identified a role for the Brucella melitensis gene bveA (BMEII0681), encoding a predicted esterase, in the resistance of B. melitensis to polymyxin B. Characterization of the enzymatic activity of BveA demonstrated that it is a phospholipase A1 with specificity for phosphatidylethanolamine (PE). Further, lipidomic analysis of B. melitensis revealed an excess of PE lipids in the bacterial membranes isolated from the bveA mutant. These results suggest that by lowering the PE content of the cell envelope, BveA increases the resistance of B. melitensis to polymyxin B. BveA was required for survival and replication of B. melitensis in macrophages and for persistent infection in mice. BveA family esterases are encoded in the genomes of the alphaproteobacterial species that coexist with the polymyxin-producing bacteria in the rhizosphere, suggesting that maintenance of a low PE content in the bacterial cell envelope may be a shared persistence strategy for association with plant and mammalian hosts.

Alterations of Metabolic and Lipid Profiles in Polymyxin-Resistant Pseudomonas aeruginosa

“…4A). A similar phenomenon was reported in Brucella melitensis, in which polymyxin resistance is associated with decreased PE content in the cell envelope (36). In contrast, LPS-deficient polymyxin-resistant isolate A. baumannii 19606R produces higher levels of GPLs than its paired polymyxin-susceptible wild-type strain, A. baumannii ATCC 19606 (33).…”

“…Determination of MICs. Polymyxin B MICs of all strains were determined with the broth microdilution method (36). Briefly, experiments were performed in 96-well polypropylene microtiter plates (42) with concentrations of polymyxin B (0 to 128 mg/liter) in CaMHB.…”

Molecular mechanisms of polymyxin resistance and detection of mcr genes

“…Moreover, the type III and IV pilin secretion system is involved in the regulation of the delivery of proteins or DNA through the bacterial cell envelope. Further, a mechanism has been described by which B. melitensis maintains a low level of phosphatidylethanolamine in the cell wall by expression of the BveA phospholipase A1 enzyme 54 . This property of the cell envelope contributes to polymyxin resistance as well as to persistence in the infected host.…”

Brucella Melitensis 16M Regulates the Effect of AIR Domain on Inflammatory Factors, Autophagy, and Apoptosis in Mouse Macrophage through the ROS Signaling Pathway

“…Smooth Brucella inhibits macrophage apoptosis, while rough Brucella induces macrophage apoptosis[5]. In Brucella -infected monocytes, the Bcl-2 family member A1 gene, which is associated with blood cell survival, is overexpressed[14]. Infected macrophage-like cells can inhibit the Fas-ligand or γ-interferon-induced apoptosis, indicating that the immune system adapts its response against the cell toxicity caused by an infection so that the infected host cells can be protected[15].…”