Abstract
The bacterial actin homolog, MreB, is highly conserved among rod-shaped bacteria and essential for growth under normal growth conditions. MreB directs the localization of cell wall synthesis and loss of MreB results in round cells and death. Using the MreB depolymerizing drug, A22, we show that changes to central metabolism through deletion of malate dehydrogenase from the tricarboxylic acid (TCA) cycle results in cells with an increased tolerance to A22. We hypothesize that deletion of malate dehydrogenase leads to the upregulation of gluconeogenesis resulting in an increase in cell wall precursors. Consistent with this idea, metabolite analysis revealed that malate dehydrogenase (mdh) deletion cells possess elevated levels of several glycolysis/gluconeogenesis compounds and the cell wall precursor, uridine diphosphate N-acetylglucosamine (UDP-NAG). In agreement with these results, the increased A22 resistance phenotype can be recapitulated through the addition of glucose to the media. Finally, we show that this increase in antibiotic tolerance is not specific to A22 but also applies to the cell wall-targeting antibiotic, mecillinam.
Highlights
The bacterial actin homolog, MreB, is a highly conserved and conditionally essential protein necessary for shape and growth in many rod-shaped human pathogens, including Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, and Vibrio cholerae (van den Ent et al, 2001; Alyahya et al, 2009)
While studying novel mechanisms of A22 resistance, we found that loss of malate dehydrogenase (Mdh), an enzyme in the tricarboxylic acid (TCA) cycle, leads to an increase in the MICA22 (Figure 1), which we hypothesize is through the induction of gluconeogenesis, leading to an increase in cell wall precursors
We propose that this accumulation of cell wall precursors results in increased minimal inhibitory concentration (MIC) of both the MreB-targeting drug A22 and the PBP2targeting drug, mecillinam through the activation of PBP1B
Summary
The bacterial actin homolog, MreB, is a highly conserved and conditionally essential protein necessary for shape and growth in many rod-shaped human pathogens, including Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, and Vibrio cholerae (van den Ent et al, 2001; Alyahya et al, 2009). Slow growth or overexpression of the cell division genes ftsZAQ can overcome the loss of mreB (Kruse et al, 2005; Bendezú and de Boer, 2008). While overexpression of the cell division genes does not prevent the cell from becoming round upon disruption of MreB, the increased levels of FtsZAQ are thought to help overcome the change in cell diameter, aiding. A22 Resistance in E. coli the round cells in dividing. It is currently unknown if over expression or deletion of other genes can overcome MreB disruption
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