A Burkholderia cenocepacia MurJ (MviN) homolog is essential for cell wall peptidoglycan synthesis and bacterial viability

作者：Mohamed Yasmine Fathy; Valvano Miguel A^*

来源：Glycobiology, 2014, 24(6): 564-576.

DOI：10.1093/glycob/cwu025

• cell wall
• cystic fibrosis
• essential gene
• flippase
• undecaprenylphosphate

The cell wall peptidoglycan (PG) of Burkholderia cenocepacia, an opportunistic pathogen, has not yet been characterized. However, the B. cenocepacia genome contains homologs of genes encoding PG biosynthetic functions in other bacteria. PG biosynthesis involves the formation of the undecaprenyl-pyrophosphate-linked N-acetyl glucosamine-N-acetyl muramic acid-pentapeptide, known as lipid II, which is built on the cytosolic face of the cell membrane. Lipid II is then translocated across the membrane and its glycopeptide moiety becomes incorporated into the growing cell wall mesh; this translocation step is critical to PG synthesis. We have investigated candidate flippase homologs of the MurJ family in B. cenocepacia. Our results show that BCAL2764, herein referred to as murJ(Bc), is indispensable for viability. Viable B. cenocepacia could only be obtained through a conditional mutagenesis strategy by placing murJ(Bc) under the control of a rhamnose-inducible promoter. Under rhamnose depletion, the conditional strain stopped growing and individual cells displayed morphological abnormalities consistent with a defect in PG synthesis. Bacterial cells unable to express MurJ(Bc) underwent cell lysis, while partial MurJ(Bc) depletion sensitized the mutant to the action of beta-lactam antibiotics. Depletion of MurJ(Bc) caused accumulation of PG precursors consistent with the notion that this protein plays a role in lipid II flipping to the periplasmic compartment. Reciprocal complementation experiments of conditional murJ mutants in B. cenocepacia and Escherichia coli with plasmids expressing MurJ from each strain indicated that MurJ(Bc) and MurJ(Ec) are functional homologs. Together, our results are consistent with the notion that MurJ(Bc) is a PG lipid II flippase in B. cenocepacia.

• 出版日期2014-6