An integrated computational and experimental study shows that C. jejuni M1cam can use organic acids and hydrogen for survival

Abstract S4

Presenter: Emily Stoakes (University of Cambridge)

Authors: Emily Stoakes (1), George M Savva (2), Ruby Coates (1), Noemi Tejera (2) Andrew Grant (1), John Wain (2,3) and Dipali Singh (2)

• 1 Department of Veterinary Medicine, University of Cambridge, Cambridge
• 2 Quadram Institute Bioscience, Norwich Research Park, Norwich
• 3 Norwich Medical School, University of East Anglia, Norwich

Campylobacter jejuni is the leading cause globally of acute bacterial gastroenteritis. In the UK contaminated poultry is the leading route into humans. High levels of Campylobacter are found in the chicken ceca and this is hypothesized to act as a hydrogen sink with Campylobacter using hydrogen as an electron donor. Campylobacter loads can be reduced through use of organic acids in chicken feed or during processing before human consumption. Organic acid washes, such as 1-2% malic, lactic, citric, tartaric, propionic and acetic acids have all been shown to reduce Campylobacter loads to varying degrees. In this study, we test the hypothesis that organic acids might promote C. jejuni survival. Independent experimental and computational approaches were used to understand the survival and metabolic capability of C. jejuni M1cam when incubated with 97 different organic acids and carbon sources in both a hydrogen rich environment and an environment containing no hydrogen. This was investigated through assaying respiration and survival using a Biolog phenotypic microarray (PM) 1 plate and independently by a genome-scale metabolic model to understand the metabolism of these sources. Respiration was assayed through the reduction of tetrazolium dye, a colour-change marker of NADH/NADPH reduction, indicating metabolic activity. Survival was assayed by measuring CFU/ml on 23 different carbon sources with and without hydrogen, and by a high-throughput 1 l growth streak assay for the remainder. Both our genome-scale metabolic model and assay under hydrogen conditions confirmed that C. jejuni M1cam can respire and survive using hydrogen as an electron donor even in the absence of carbon sources. Our results also showed that C. jejuni M1cam was able to respire and survive using organic acids such as malic, lactic, pyruvic acids, intermediates of the citric acid cycle. On the other hand, it was not able to respire, and thus survive, on organic acids such as Tween 80, propionic, tartaric acids. This was independently confirmed by our genome-scale computational model. This study suggests that organic acids may provide nutrient sources and allow longer survival for Campylobacter if used during food processing.

Presenting in Speaking session 4 - Survival and application