The pattern and kinetics of substrate metabolism of Campylobacter jejuni and Campylobacter coli K.A.S. Mohammed, R.J. Miles* and M.A. Halablab Department of Life Sciences, King’s College London, Franklin-Wilkins Building, London, UK 2003/0360: received 30 April 2003, revised 1 June 2004 and accepted 1 June 2004 ABSTRACT K.A.S. MOHAMMED, R.J. MILES AND M.A. HALABLAB. 2004. Aims: The main aim was to investigate the patterns and kinetics of substrate oxidation by Campylobacter jejuni and C. coli. Methods and Results: Substrate oxidation profiles by 100 strains were determined using oxygen electrode system. All the isolates tested oxidized formate, L-lactate, cysteine, glutamine and serine with high oxidation rates and high affinity but varied in their ability to oxidize citric acid cycle intermediates, aspartic acid and serine. Conclusions: Based on the oxidation ability of a-ketoglutarate, succinate, fumarate and aspartic acid, Campylobacter strains tested were divided into three distinct metabolic categories. The first group was able to metabolize a-ketoglutarate, succinate, fumarate and aspartic acid; the second group was unable to oxidize a-ketoglutarate; and the third group was unable to oxidize, succinate, fumarate, and aspartic acid. Furthermore, serine oxidation rate enabled the differentiation of C. jejuni and C. coli. Significance and Impact of the Study: Overall, the results highlights the extensive metabolic diversity between and within Campylobacter species. In addition, the kinetic data of oxidized substrates obtained may improve the isolation procedures of the organism. Keywords: Campylobacter, citric acid cycle, kinetics, metabolism, oxygen electrode. INTRODUCTION A number of Campylobacter species may be involved in human gastrointestinal disease, but the majority are caused by C. jejuni and C. coli (Tauxe 1992; Frost et al. 2002). Despite its importance in disease, the metabolism and the physiology of Campylobacter is poorly understood. In particular, energy metabolism and the significance of potential energy substrate is still not completely known. This lack of information impeded the full elucidation of survival, transmission and the pathogenicity of Campylobac- ter. Previous studies on Campylobacter metabolism (Alexan- der 1957; Kiggins and Plastridge 1958; Zemjanis and Hoyt 1960; Smibert 1963; Hoffman 1979; Veron et al. 1981; Elharrif and Megraud 1986; Karmali et al. 1986; Westfall et al. 1986; Mendz et al. 1997) were, mostly, based on investigation of substrate utilization in growth media and rarely derived kinetics data of these substrates studied. It was found that citric acid cycle (CAC) intermediates, but not carbohydrates, can serve as excellent energy source for Campylobacter (Alexander 1957). Kiggins and Plastridge 1958 demonstrated rapid oxygen uptake with all members of the CAC when the crude cellular extract of C. fetus was employed; whereas whole cells showed only slight or no oxygen uptake with citrate, cis-aconitate, isocitrate and ketogluterate. Employing oxygen electrode apparatus, Hoff- man 1979 determined the oxygen uptake rate for three strains of C. fetus in response to CAC intermediates. In addition to the latter, campylobacters were able to oxidize at least six different amino acids. (Alexander 1957; Kiggins and Plastridge 1958; Elharrif and Megraud 1986). Most of these Correspondence to: M.A. Halablab, Department of Life Sciences, King’s College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NN, UK (e-mail: mahmoud.halablab@kcl.ac.uk). *Deceased 25 October 2001. ª 2004 The Society for Applied Microbiology Letters in Applied Microbiology 2004, 39, 261–266 doi:10.1111/j.1472-765X.2004.01574.x