Transport of the abundant intestinal amino acid glutamine by the enteric pathogen Campylobacter jejuni occurs via GutA (Cj0903), an AGCS family transporter

Glutamine is the most abundant amino acid in the human body, playing a crucial role in numerous cellular processes. Notably for enteric bacteria, glutamine is abundant in the intestines where it helps to maintain gut health of the host, therefore presenting itself as an accessible nutrient. <i>Campylobacter jejuni</i>, a largely non-saccharolytic organism, favours just a few amino acids for growth, and glutamine is particularly efficient as a nitrogen source. Despite this, a glutamine transporter has not been conclusively identified in this important human pathogen. By measuring the global transcriptomic response of <i>C. jejuni</i> to replete glutamine conditions, we identified several candidate transporters, ultimately characterising Cj0903, here named glutamine uptake transporter A, as the major glutamine transporter belonging to the alanine or glycine:cation symporter family. We show that this transporter is ubiquitous in thermotolerant <i>Campylobacter</i>, demonstrating a conserved ability to utilise exogenous glutamine. In contrast, the ammonium transporter Amt was only present in a subset of <i>C. jejuni</i>, and we confirmed that <i>amt</i> negative isolates do not effectively utilise ammonium as a nitrogen source.