Analysis of the LIV System of Campylobacter jejuni Reveals Alternative Roles for LivJ and LivK in Commensalism beyond Branched-Chain Amino Acid Transport

Abstract

Campylobacter jejuni is a leading cause of diarrheal disease in humans and an intestinal commensal in poultry and other agriculturally important animals. These zoonotic infections result in significant amounts of C. jejuni present in the food supply to contribute to disease in humans. We previously found that a transposon insertion in Cjj81176_1038, encoding a homolog of the Escherichia coli LivJ periplasmic binding protein of the leucine, isoleucine, and valine (LIV) branched-chain amino acid transport system, reduced the commensal colonization capacity of C. jejuni 81-176 in chicks. Cjj81176_1038 is the first gene of a six-gene locus that encodes homologous components of the E. coli LIV system. By analyzing mutants with in-frame deletions of individual genes or pairs of genes, we found that this system constitutes a LIV transport system in C. jejuni responsible for a high level of leucine acquisition and, to a lesser extent, isoleucine and valine acquisition. Despite each LIV protein being required for branched-chain amino acid transport, only the LivJ and LivK periplasmic binding proteins were required for wild-type levels of commensal colonization of chicks. All LIV permease and ATPase components were dispensable for in vivo growth. These results suggest that the biological functions of LivJ and LivK for colonization are more complex than previously hypothesized and extend beyond a role for binding and acquiring branched-chain amino acids during commensalism. In contrast to other studies indicating a requirement and utilization of other specific amino acids for colonization, acquisition of branched-chain amino acids does not appear to be a determinant for C. jejuni during commensalism.

Contribution of Amino Acid Catabolism to the Tissue Specific Persistence of Campylobacter jejuni in a Murine Colonization Model

“…Unlike other enteropathogenic bacteria C. jejuni is unable to use glucose as growth substrate [35] and only a subset of C. jejuni isolates harbor a fucP gene cluster that facilitates the catabolism of fucose [36], [37]. Instead of carbohydrates, the glucogenic amino acids aspartate, asparagine, glutamate, glutamine, proline and serine represent important nutrients fueling the in vitro growth of C. jejun i [38]–[40], [42], [43], [45], [55], [68].…”

“…While it is well documented that amino acids represent major energy and carbon sources for the in vitro growth of C. jejuni , only a few studies have examined the contribution of amino acid catabolism to bacterial colonization. For example, serine and aspartate catabolism were shown to be important for C. jejuni colonization of the avian gut [38], [45] and mutation of a putative branched amino acid transporter resulted in an attenuated colonization phenotype in chicken [20], [55]. The γ-glutamyltranspeptidase (GGT) dependent utilization of glutamine and glutathione by C. jejuni 81-176 supports the colonization of the murine intestine [51].…”

Characterization of Intracellular Growth Regulator icgR by Utilizing Transcriptomics To Identify Mediators of Pathogenesis in Shigella flexneri

“…LivHMGF are membrane components that are shared between both systems (47). Previous studies have demonstrated that liv mutants in Campylobacter jejuni are unable to colonize chicks (48) and that liv mutants in Streptococcus pneumoniae are attenuated in mice (49). These studies suggest a role for leucine, isoleucine, and valine transporters in in vivo growth and pathogenesis.…”

Identification of Bacterial Genes Expressed During Diatom-Bacteria Interactions Using an in Vivo Expression Technology Approach

“…Interestingly, the gene product of livK was already found upregulated in our previous proteomics study (Stahl and Ullrich, 2016). LivK is part of a branched amino acid uptake system transporting leucine, isoleucine, and valine (Adams et al, 1990;Ribardo and Hendrixson, 2011). LivK's functional involvement in branched amino acid transport in M. adhaerens HP15 is supported by the close proximity of genes encoding the inner membrane translocators LivH and LivG as well as the ATP binding components LivM and LivF (Adams et al, 1990).…”