A Putative Acetylation System in Vibrio cholerae Modulates Virulence in Arthropod Hosts

Abstract

Acetylation is a broadly conserved mechanism of covalently modifying the proteome to precisely control protein activity. In bacteria, central metabolic enzymes and regulatory proteins, including those involved in virulence, can be targeted for acetylation. In this study, we directly link a putative acetylation system to metabolite-dependent virulence in the pathogen We demonstrate that the and genes, which encode homologs of a deacetylase and an acetyltransferase, respectively, modulate metabolism of acetate, a bacterially derived short-chain fatty acid with important physiological roles in a diversity of host organisms. In , a model arthropod host for infection, the pathogen consumes acetate within the gastrointestinal tract, which contributes to fly mortality. We show that deletion of impairs growth on acetate minimal medium, delays the consumption of acetate from rich medium, and reduces virulence of toward These impacts can be reversed by complementing or by introducing a deletion of into the Δ background. We further show that controls the accumulation of triglycerides in the midgut, which suggests that directly modulates metabolite levels In K-12, is upregulated by cAMP-cAMP receptor protein (CRP), and we identified a similar pattern of regulation in , arguing that the system is activated in response to similar environmental cues. In summary, we demonstrate that proteins likely involved in acetylation can modulate the outcome of infection by regulating metabolite exchange between pathogens and their colonized hosts. The bacterium causes severe disease in humans, and strains can persist in the environment in association with a wide diversity of host species. By investigating the molecular mechanisms that underlie these interactions, we can better understand constraints affecting the ecology and evolution of this global pathogen. The model of infection has revealed that bacterial regulation of acetate and other small metabolites from within the fly gastrointestinal tract is crucial for its virulence. Here, we demonstrate that genes that may modify the proteome of affect virulence toward , most likely by modulating central metabolic pathways that control the consumption of acetate as well as other small molecules. These findings further highlight the many layers of regulation that tune bacterial metabolism to alter the trajectory of interactions between bacteria and their hosts.

Regulatory Effects of CsrA in Vibrio cholerae

“…This finding suggests that CsrA may exert large regulatory effects on the V. cholerae transcriptome by controlling the expression of other regulators. Consistent with our observation that CsrA is required for virulence within the host, we identified multiple CsrA-interacting mRNAs associated with pathogenesis, including the following: aphA (26); flrC (27); epsC, which encodes a component of the type two secretion system that is responsible for the secretion of the cholera toxin (28); cobB, which encodes an NAD1 dependent deacetylase (29); and VCA0965, encoding a functional cyclic di-GMP synthase (30). Selected regulators are discussed in more detail below.…”

“…The acetate switch promotes the transition from acetate excretion during rapid growth to acetate assimilation when other, preferred, carbon sources become depleted. Expression of genes involved in the acetate switch, including genes encoding the two-component system CrbRS (VC0303/VC2702), a putative cation-acetate symporter system (VC2704/VC2705), acetyl-CoA synthase (VC0298) (50), and CobB (VC1509), which activates the acetyl-CoA synthase through deacetylation (29), was reduced in the csrA mutant at stationary phase, consistent with positive regulation of these genes by CsrA. Although the statistical threshold for inclusion in the data set (P , 0.05) was not met in every case for these genes, the overall trend in gene expression suggests that V. cholerae is no longer excreting acetate via glycolysis and mixed acid fermentation in stationary phase, but is instead taking up acetate from the medium and using it in the TCA cycle in a CsrA-dependent process.…”

Protein Acetylation in Bacteria

“…This Pat protein contains a regulatory domain of unknown function (~700 amino acids) attached to the catalytic GNAT domain (~200 amino acids). Recent work also highlights the importance of Acs acetylation and deacetylation during bacterial infections (44). Using Vibrio cholerae and Drosophila melanogaster as an infection model, it was found that dysregulation of Acs acetylation reduced V. cholera virulence.…”

“…Using Vibrio cholerae and Drosophila melanogaster as an infection model, it was found that dysregulation of Acs acetylation reduced V. cholera virulence. This work emphasizes the impact of protein acetylation on the physiology of pathogenic bacteria that affect human health across the world (44). While many studies characterizing Acs acetylation by Pat have similarities, there are also differences worth discussing here.…”

Mechanisms, Detection, and Relevance of Protein Acetylation in Prokaryotes

“…YfiQ is a conserved acetyltransferase (12) with homologs found across many bacterial species, including E. coli (69), Vibrio cholerae (5), Salmonella enterica (70), Yersinia pestis (10), Rhodopseudomonas palustris (71), Streptomyces lividans (72), and Streptomyces griseus (73). The best-understood role for YfiQ is acetylation of acetyl-CoA synthetase (Acs); acetylation inactivates Acs, preventing acetate consumption (70).…”