Novel role for peptidoglycan carboxypeptidases in maintaining the balance between bacterial cell wall synthesis and degradation
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Abstract
Peptidoglycan (PG) is the main component of the bacterial cell wall; it maintains cell shape while protecting the cell from internal osmotic pressure and external environmental challenges. PG synthesis is essential for bacterial growth and survival, and a series of PG modifications are required to allow expansion of the sacculus. Endopeptidases (EPs), for example, cleave the crosslinks between adjacent PG strands to allow the incorporation of newly synthesized PG. EPs are collectively essential for bacterial growth and must likely be carefully regulated to prevent sacculus degradation and cell death. However, EP regulation mechanisms are poorly understood. Here, we used TnSeq to uncover novel EP regulation factors in Vibrio cholerae . This screen revealed that the carboxypeptidase DacA1 (PBP5) alleviates EP toxicity. dacA1 is essential for viability on LB medium, and this essentiality was suppressed by EP overexpression, revealing that EP toxicity both mitigates, and is mitigated by, a defect in dacA1 . A subsequent suppressor screen to restore viability of ΔdacA1 in LB medium was answered by hypomorphic mutants in the PG synthesis pathway, as well as mutations that promote PG degradation. Our data thus reveal a key role of DacA1 in maintaining the balance between PG synthesis and degradation.
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Thank you for a very well done paper! I did my postdoc on Tae1, a P. aeruginosa T6S toxin with a peptidoglycan endopeptidase activity. I really enjoy thinking about the balance between peptidoglycan synthesis and degradation! There were many really cool ideas in your paper! I found this statement really intriguing: "locally reduced EP activity might create expansive stretches of PG with pentapeptide-rich second layers". Have you thought about how the EP activity could be reduced locally? Do you think it's possible that some of the endogenous EP enzymes recognize a specific PG topology or architecture, like the areas that have two-layers or perhaps densely cross-linked areas? It's super interesting to think how PG enzymes recognize different topological features of the cell wall and your paper really spurred my imagination. Thank you so …
Thank you for a very well done paper! I did my postdoc on Tae1, a P. aeruginosa T6S toxin with a peptidoglycan endopeptidase activity. I really enjoy thinking about the balance between peptidoglycan synthesis and degradation! There were many really cool ideas in your paper! I found this statement really intriguing: "locally reduced EP activity might create expansive stretches of PG with pentapeptide-rich second layers". Have you thought about how the EP activity could be reduced locally? Do you think it's possible that some of the endogenous EP enzymes recognize a specific PG topology or architecture, like the areas that have two-layers or perhaps densely cross-linked areas? It's super interesting to think how PG enzymes recognize different topological features of the cell wall and your paper really spurred my imagination. Thank you so much!
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