Localized perforation of the cell wall by a major autolysin: atl gene products and the onset of penicillin-induced lysis of Staphylococcus aureus

Abstract

We investigated the cell surface localization of the atl gene products of Staphylococcus aureus exposed to a lytic concentration (4 MIC) of penicillin G (PCG) by means of immunoelectron microscopy using anti-62-kDa N-acetylmuramyl-L-alanine amidase or anti-51-kDa endo-␤-N-acetylglucosaminidase immunoglobulin G. Protein A-gold conjugates reacting with antigen-antibody complex localized at sites of defects of the cell wall at the nascent cross wall. Anti-62-kDa N-acetylmuramyl-L-alanine amidase or anti-51-kDa endo-␤-N-acetylglucosaminidase immunoglobulin G inhibited the decreased turbidity caused by PCG-induced lysis and the formation of defects in the wall. The autolysis-defective mutant, S. aureus RUSAL2 (atl::Tn551), exposed to 4 MIC of PCG resisted autolysis and formation of the wall defect. These results suggest that activation or deregulation of the atl gene products at localized sites where formation of new cross wall was disturbed by PCG causes small defects in the cell wall in situ, eventually leading to general autolysis.

Molecular Characterization of an atl Null Mutant of Staphylococcus aureus

“…Interestingly, the complemented mutant JT1310 did not fully restore the lytic trait of the wild type but reached a plateau at OD 660 nm 0.4. We have previously demonstrated that penicillin-induced lysis, but not decrease in CFU, can be blocked by the addition of anti-Atl antibody (28). Thus, as expected, the rate of loss of viability during penicillin treatment of RN4220, JT1392 and JT1310 was similar, indicating that atl mutation did not protect cells from PCG-induced cell killing (data not shown).…”

“…These results suggested that the atl gene products are involved in cell separation. In a separate experiment, antisera against atl gene products showed an inhibitory effect on lysis of S. aureus incubated with lytic concentration of penicillin G (PCG) (28). This suggested that the atl gene products can also act as autolysins involved in PCG-induced lysis of the cells.…”

Cell-wall determinants of the bactericidal action of group IIA phospholipase A2 against Gram-positive bacteria

“…Because the lyt + and lyt -strains of S. aureus are equally susceptible to phospholipid degradation by PLA 2 , differences in their autolytic activity (9) pholipids further points to remarkable repair capabilities of the bacteria in the absence of autolytic activity. The activities of autolysins are tightly regulated (27), both temporally and spatially, to permit the discrete action needed for cell-wall biogenesis (16,18,19), without causing diffuse cell-wall alterations that would be harmful to the bacteria. Because the growth rates of the lyt + and lyt -strains are comparable, the actual level of autolytic activity coupled to cell growth processes may be similar in both strains, despite the large difference in overall autolytic activity.…”

“…Bacterial cell-wall-degrading enzymes (autolysins) play an important role in cell-wall morphogenesis that accompanies cell growth, division/separation, and peptidoglycan turnover (16,17). Thus, these enzymes could contribute to the greater sensitivity of growing bacteria to PLA 2 action by producing localized sites of weakened and thinned peptidoglycan (18,19). To test this hypothesis, we compared the sensitivity of S. aureus RN450 (lyt + ) and an isogenic, autolysis-deficient mutant (Lyt -) to PLA 2 .…”

Dual Targeting of Cell Wall Precursors by Teixobactin Leads to Cell Lysis

“…␤-Lactam-induced lysis is known to be mediated by Atl, the major cell wall autolysin of S. aureus (17,22). To investigate the contribution of Atl to the activity of teixobactin, the antibacterial activity against an ⌬atl mutant from the Nebraska transposon insertion library (available through BEI [https://www .beiresources.org/]) was examined and compared to wild-type strain JE2.…”