Two respiratory enzyme systems in Campylobacter jejuni NCTC 11168 contribute to growth on l‐lactate

Abstract

Campylobacter jejuni, a major food-borne intestinal pathogen, preferentially utilizes a few specific amino acids and some organic acids such as pyruvate and L- and D-lactate as carbon sources, which may be important for growth in the avian and mammalian gut. Here, we identify the enzymatic basis for C. jejuni growth on L-lactate. Despite the presence of an annotated gene for a fermentative lactate dehydrogenase (cj1167), no evidence for lactate excretion could be obtained in C. jejuni NCTC 11168, and inactivation of the cj1167 gene did not affect growth on lactate as carbon source. Instead, L-lactate utilization in C. jejuni NCTC 11168 was found to proceed via two novel NAD-independent L-LDHs; a non-flavin iron-sulfur containing three subunit membrane-associated enzyme (Cj0075c-73c), and a flavin and iron-sulfur containing membrane-associated oxidoreductase (Cj1585c). Both enzymes contribute to growth on L-lactate, as single mutants in each system grew as well as wild-type on this substrate, while a cj0075c cj1585c double mutant showed no L-lactate oxidase activity and did not utilize or grow on L-lactate; D-lactate-dependent growth was unaffected. Orthologues of Cj0075c-73c (LldEFG/LutABC) and Cj1585c (Dld-II) were recently shown to represent two novel families of L- and D-lactate oxidases; this is the first report of a bacterium where both enzymes are involved in L-lactate utilization only. The cj0075c-73c genes are located directly downstream of a putative lactate transporter gene (cj0076c, lctP), which was also shown to be specific for L-lactate. The avian and mammalian gut environment contains dense populations of obligate anaerobes that excrete lactate; our data indicate that C. jejuni is well equipped to use L- and D-lactate as both electron-donor and carbon source.

Selenium-Dependent Biogenesis of Formate Dehydrogenase in Campylobacter jejuni Is Controlled by the fdhTU Accessory Genes

“…Inactivation and complementation of C. jejuni genes was performed essentially as described previously (36). Specific C. jejuni genes were inactivated by the replacement and insertion of antibiotic resistance cassettes (kanamycin or chloramphenicol).…”

FdhTU-Modulated Formate Dehydrogenase Expression and Electron Donor Availability Enhance Recovery ofCampylobacter jejunifollowing Host Cell Infection

“…C. jejuni has a branched respiration system and is able to use a wide range of compounds as electron donors and acceptors (26,30,56,76,81). Furthermore, formate, sulfite, and hydrogen gas are abundant as by-products of commensal bacterial fermentative metabolism, from normal metabolism of amino acids, and as food additives (12,17,77).…”

An Unconventional Hexacoordinated Flavohemoglobin from Mycobacterium tuberculosis

“…Spectrofluorometric Analysis of FAD Associated with MtbFHb-The potential association of FAD with MtbFHb, MtbFHb RD , and MtbFHb FAD was checked by published procedure (23). Briefly, the flavin cofactor associated with the protein was extracted after boiling for 5 min and centrifuging at 14,000 rpm for 20 min.…”