AbstractRod-shaped bacteria have two modes of peptidoglycan synthesis: lateral synthesis and synthesis at the cell division site. These two processes are controlled by two macromolecular protein complexes, the elongasome and divisome. Recently, it has been shown that theBacillus subtilisRodA protein, which forms part of the elongasome, has peptidoglycan glycosyltransferase activity. The cell division specific RodA homolog FtsW fulfils a similar role at the divisome. The human pathogenListeria monocytogenesencodes up to six FtsW/RodA homologs, however their functions have not yet been investigated. Analysis of deletion and depletion strains led to the identification of the essential cell division-specific FtsW protein, FtsW1. Interestingly,L. monocytogenesencodes a second FtsW protein, FtsW2, which can compensate for the lack of FtsW1, when expressed from an inducible promoter.L. monocytogenesalso possesses three RodA homologs, RodA1, RodA2 and RodA3 and their combined absence is lethal. Cells of arodA1/rodA3double mutant are shorter and have increased antibiotic and lysozyme sensitivity, probably due to a weakened cell wall. Results from promoter activity assays revealed that expression ofrodA3andftsW2is induced in the presence of antibiotics targeting penicillin binding proteins. Consistent with this, arodA3mutant was more susceptible to the β-lactam antibiotic cefuroxime. Interestingly, overexpression of RodA3 also led to increased cefuroxime sensitivity. Our study highlights thatL. monocytogenesencodes a multitude of functional FtsW and RodA enzymes to produce its rigid cell wall and that their expression needs to be tightly regulated to maintain growth, cell division and antibiotic resistance.ImportanceThe human pathogenListeria monocytogenesis usually treated with high doses of β-lactam antibiotics, often combined with gentamicin. However, these antibiotics only act bacteriostatically onL. monocytogenesand the immune system is needed to clear the infection. Therefore, individuals with a compromised immune system are at risk to develop a severe form ofListeriainfection, which can be fatal in up to 30% of cases. The development of new strategies to treatListeriainfections is therefore necessary. Here we show that the expression of some of the FtsW and RodA enzymes ofL. monocytogenesis induced by the presence of β-lactam antibiotics and their combined absence makes bacteria more susceptible to this class of antibiotics. The development of antimicrobials that inhibit the activity or production of FtsW/RodA enzymes might therefore help to improve the treatment ofListeriainfections and thereby lead to a reduction in mortality.
Occurrence, Antibiotic Resistance, and Population Diversity of Listeria monocytogenes Isolated From Fresh Aquatic Products in China
