Instituto Universitario de Biología Molecular

Bacterial cell envelope during preseptal growth

Dr. Manuel Pazos Don Pedro. Investigador Talento CAM.

The research in the laboratory focuses on understanding the molecular mechanisms underpinning the biogenesis of the bacterial cell envelope of model and pathogenic gastrointestinal organisms (e.g. Escherichia coli) during preseptal growth, in the context of physiology and pathogenicity.

The peptidoglycan (PG) sacculus is an essential structural component of most bacterial cell envelopes, and its synthesis is one of the most frequently targeted process by antibiotics. Since the rise of antimicrobial resistance is making infections harder to treat, with special emphasis to those caused by Gram-negative bacteria due to their extra outer membrane barrier, it is crucial to understand how the cell envelope integrity is maintained during the bacterial cell cycle. The cell envelope integrity is essential for the physiology and pathogenicity of bacteria, and therefore both peptidoglycan and membrane synthesis machineries are coordinated and regulated to ensure the robust growth of the cell envelope.

Contrary to cell elongation and cell division, which have been studied in greater depth, the transition between both stages called preseptal growth remains poorly characterized. This switch involves the incorporation of new PG material at mid-cell before the septum is formed. In previous work we described the connection between the cytosolic FtsZ polymers and the PG synthases (PBP1A and PBP1B) through the partially redundant proteins ZipA and FtsA-FtsN. The disruption of both connections disables the incorporation of new preseptal PG, leading to non-viable filamented cells, identifying the preseptal PG growth as an essential process occurring prior cell division (Pazos et al. 2018, Nat Commun 9:5090). These results would answer the long-standing question about the mechanism by which single-point mutations in FtsA are able to bypass the requirement of ZipA for cell division and preseptal PG synthesis.

In addition, we described for the first time how the PG-binding SPOR proteins DamX and DedD are required for full functionality of the PG synthases PBP1A and PBP1B, and the lethal effect of an unbalanced DedD:DamX protein ratio (Pazos et al. 2020, mBio 11:e02796-20). SPOR domains are widely spread and conserved in bacterial proteins, making them promising target to interfere with bacterial cell envelope synthesis.

To accomplish our ultimate goal of identifying new potential antimicrobial targets, we aim to use a multidisciplinary approach combining genetics, biochemistry, cell biology and different microscopy techniques to characterize the molecular components and cell envelope features during this potentially vulnerable stage of the bacterial cell cycle.