Aerobic Metabolism in Vibrio cholerae Is Required for Population Expansion during Infection

Abstract

Vibrio cholerae replicates to high cell density in the human small intestine, leading to the diarrheal disease cholera. During infection, V. cholerae senses and responds to environmental signals that govern cellular responses. Spatial localization of V. cholerae within the intestine affects nutrient availability and metabolic pathways required for replicative success. Metabolic processes used by V. cholerae to reach such high cell densities are not fully known. We sought to better define the metabolic traits that contribute to high levels of V. cholerae during infection. By disrupting the pyruvate dehydrogenase (PDH) complex and pyruvate formate-lyase (PFL), we could differentiate aerobic and anaerobic metabolic pathway involvement in V. cholerae proliferation. We demonstrate that oxidative metabolism is a key contributor to the replicative success of V. cholerae in vivo using an infant mouse model in which PDH mutants were attenuated 100-fold relative to the wild type for colonization. Additionally, metabolism of host substrates, including mucin, was determined to support V. cholerae growth in vitro as a sole carbon source, primarily under aerobic growth conditions. Mucin likely contributes to population expansion during human infection as it is a ubiquitous source of carbohydrates. These data highlight oxidative metabolism as important in the intestinal environment and warrant further investigation of how oxygen and other host substrates shape the intestinal landscape that ultimately influences bacterial disease. We conclude from our results that oxidative metabolism of host substrates is a key driver of V. cholerae proliferation during infection, leading to the substantial bacterial burden exhibited in cholera patients. IMPORTANCE Vibrio cholerae remains a challenge in the developing world and incidence of the disease it causes, cholera, is anticipated to increase with rising global temperatures and with emergent, highly infectious strains. At present, the underlying metabolic processes that support V. cholerae growth during infection are less well understood than specific virulence traits, such as production of a toxin or pilus. In this study, we determined that oxidative metabolism of host substrates such as mucin contribute significantly to V. cholerae population expansion in vivo. Identifying metabolic pathways critical for growth can provide avenues for controlling V. cholerae infection and the knowledge may be translatable to other pathogens of the gastrointestinal tract.

Oxidative respiration through the bd-I and cbb3 oxidases is required for Vibrio cholerae pathogenicity and proliferation in vivo

“…However, the contribution of ArcA to El Tor V. cholerae colonization and pathogenicity has yet to be explored. It is not unlikely there may be different mechanisms of ArcA regulation between Classical and El Tor V. cholerae, as the Classical biotype is incapable of producing cholera toxin under anaerobiosis [53] whereas the El Tor biotype can produce cholera toxin anaerobically [6]. Oxygen sensing may also drive a chemotactic response in V. cholerae through aerotactic chemoreceptors Aer1 [54] and Aer2 [55], however this oxygen response pathway is unlikely to be required in vivo as non-chemotactic V. cholerae nevertheless colonize the infant mouse intestine [56].…”

“…Respiration in V. cholerae is achieved aerobically through the terminal reduction of molecular oxygen or anaerobically through the terminal reduction of various alternative electron acceptors [4,5]. Recent evidence suggests there is combined contribution of both aerobic and anaerobic metabolism to V. cholerae growth in vivo [6,7]. This may be attributed to the radial and longitudinal gradients of oxygen availability in the intestinal tract enabling metabolism through both pathways in response to in vivo localization [8].…”

The Interface of Vibrio cholerae and the Gut Microbiome

“…158 V. cholerae uses pyruvate dehydrogenase (PDH) to expand in the small intestine, rather than pyruvate formate-lyase (PFL) mediated anaerobic metabolism to convert pyruvate to acetyl coenzyme A (acetyl-CoA), which provides growth support during infection. 159 Moreover, the cholera toxin (CTX)-induced increase of cAMP can induce host cells to switch to anaerobic respiration, leading to host reduced consumption of oxygen. 160 However, under hypoxic conditions, V. cholerae is able to employ several alternative electron acceptors (AEA) such as fumarate, trimethylamine N-oxide (TMAO), and NO 3 .…”

“…180 Mucin degradation is also associated with the pathogenicity of enteric invaders. 159 Toxigenic strains of V. cholerae contain the nan cluster on the pathogenicity island VPI2, which allows the use of sialic acid as a carbon source. 181 Inactivation of sialic acid utilization caused a decreased colonization of V. cholerae in an infant mouse model, 182 while the mucus components GlcNAc and NeuAc promote V. cholerae motility.…”

“…183 Genes involved in the metabolism of those mucin glycans can be found in gut microbial commensals, such as species from Bacteroides, Lactobacillus, Bifidobacterium, and Akkermansia muciniphila. 159,184,185 Thus, the ability of different assemblages of commensal bacteria to metabolize mucin may be an important driver of V. cholerae fitness in the gut. Prior work highlights the potential for this interaction; the presence of mucin glycan utilizers in the gut such as A. muciniphila, Bacteroides intestinihominis, and the generalist carbohydrate utilizers Bacteroides thetaiotaomicron, and Bacteroides caccae can increase C. rodentium susceptibility due to the enhanced mucus degradation, 186 while other studies have used consortia of commensal metabolizes of mucus components to deny these resources to C. difficile and thus inhibit colonization.…”