Contribution of penicillin-binding protein homologs to antibiotic resistance, cell morphology, and virulence of Listeria monocytogenes EGDe

Abstract

Seven open reading frames, annotated as potential penicillin-binding-protein-encoding genes (lmo0441, lmo0540, lmo1438, lmo1892, lmo2039, lmo2229, and lmo2754), were targeted for insertional mutagenesis in Listeria monocytogenes EGDe. These genes were found to contribute in various degrees to beta-lactam resistance, cell morphology, or the virulence potential of this organism.

FIG. 1.

(a) Effect of disruption of lmo2754 on the invasion of the organism on C2Bbe1 cells. Numbers of L. monocytogenes cells invaded were expressed as log CFU/well. Results are representative of triplicate experiments. (b) Effect of pORI19 disruption of PBPs on the survival of EGDe in vivo. Numbers indicate the genes that were disrupted. Mice were injected intraperitoneally, and the number of bacteria recovered from the spleen was determined at 3 days postinfection. Error bars represent the standard deviations from the means (n = 5). *, mean is statistically significant with respect to the wild-type value (P < 0.05).

FIG. 2.

Electron microscopy of EGDe (a) pORI19::0441 (b), pORI19::0540 (c), pORI19::1438 (d), pORI19::1892 (e), pORI19::2229 (f), and pORI19::2754 (g). Arrows in panels b and e indicate irregular curving of cells and increased cell length. Arrows in panel f indicate filamenting of cells. Arrows in panel g indicate irregular shapes of cells.