| Abstract: | Peptidoglycan (PG) is a highly cross‐linked polysaccharide that encases bacteria, resists the effects of turgor and confers cell shape. PG precursors are translocated across the cytoplasmic membrane by the lipid carrier undecaprenyl phosphate (Und‐P) where they are incorporated into the PG superstructure. Previously, we found that one of our Escherichia coli laboratory strains (CS109) harbors a missense mutation in uppS, which encodes an enzymatically defective Und‐P(P) synthase. Here, we show that CS109 cells lacking the bifunctional aPBP PBP1B (penicillin binding protein 1B) lyse during exponential growth at elevated temperature. PBP1B lysis was reversed by: (i) reintroducing wild‐type uppS, (ii) increasing the availability of PG precursors or (iii) overproducing PBP1A, a related bifunctional PG synthase. In addition, inhibiting the catalytic activity of PBP2 or PBP3, two monofunctional bPBPs, caused CS109 cells to lyse. Limiting the precursors required for Und‐P synthesis in MG1655, which harbors a wild‐type allele of uppS, also promoted lysis in mutants lacking PBP1B or bPBP activity. Thus, simultaneous inhibition of Und‐P production and PG synthases provokes a synergistic response that leads to cell lysis. These findings suggest a biological connection that could be exploited in combination therapies. |
