Campylobacter jejuni, from the delta-epsilon group of proteobacteria, is a microaerophilic, Gram-negative, flagellate, spiral bacterium-properties it shares with the related gastric pathogen Helicobacter pylori. It is the leading cause of bacterial food-borne diarrhoeal disease throughout the world. In addition, infection with C. jejuni is the most frequent antecedent to a form of neuromuscular paralysis known as Guillain-Barré syndrome. Here we report the genome sequence of C. jejuni NCTC11168. C. jejuni has a circular chromosome of 1,641,481 base pairs (30.6% G+C) which is predicted to encode 1,654 proteins and 54 stable RNA species. The genome is unusual in that there are virtually no insertion sequences or phage-associated sequences and very few repeat sequences. One of the most striking findings in the genome was the presence of hypervariable sequences. These short homopolymeric runs of nucleotides were commonly found in genes encoding the biosynthesis or modification of surface structures, or in closely linked genes of unknown function. The apparently high rate of variation of these homopolymeric tracts may be important in the survival strategy of C. jejuni.

Attenuated Vibrio cholerae vaccine strains specifically mutated in genes encoding cholera toxin (CT) are still capable of causing mild to moderate diarrhea. Culture supernatants of V. cholerae strains, both CT-positive and CT-negative, were examined in Ussing chambers, and a toxin was found that increases the permeability of the small intestinal mucosa by affecting the structure of the intercellular tight junction, or zonula occludens. The activity of this toxin is reversible, heat-labile, sensitive to protease digestion, and found in culture supernatant fractions containing molecules between 10 and 30 kDa in size. Production ofthis factor (named ZOT for zonula occludens toxin) correlates with diarrheagenicity of V. cholerae strains in volunteers and may represent another virulence factor of infectious diarrhea that must be eliminated to achieve a safe and effective live oral vaccine against cholera.Vibrio cholerae produces the copious diarrhea characteristic of cholera by means of a potent enterotoxin, cholera toxin (CT). The A subunit of CT, encoded by ctxA, stimulates adenylate cyclase in intestinal epithelial cells, which results in net secretion of fluid into the intestinal lumen (1). Initial recombinant V. cholerae vaccine strains, attenuated by removal of the ctxA gene, were greatly reduced in their ability to induce diarrhea in volunteers (2). However, despite the absence of CT, these strains were still capable of inducing an unacceptable amount of diarrhea. One such strain, V. cholerae CVD101, is a ctxA deletion mutant of V. cholerae strain 395 in which 94% of the sequence encoding the A1 peptide of CT has been removed (3). When evaluated in volunteer studies, CVD101 caused mild to moderate diarrhea (mean stool volume of 0.9 liter with a range of 0.3-to 2.1 liters) in 54% of subjects ingesting this organism (2). While greatly attenuated compared with the parent strain 395 [which induces a mean diarrheal stool volume of 5.5 liters with a range of 0.3-44 liters in >90% of volunteers (4)], the amount of diarrhea induced by CVD101 is still unacceptable for use of this strain as a vaccine.Given the magnitude of the diarrhea induced in the absence of CT, we hypothesized that V. cholerae produced a second toxin, which was still present in strains deleted of the ctxA sequence. To investigate this hypothesis, we examined V. cholerae strains with and without intact ctx genes by using rabbit intestinal tissue mounted in Ussing chambers, a classic technique for studying the process of transport across intestinal tissue (5, 6). The results indicate that V. cholerae produces a toxin that increases intestinal tissue conductance by altering the structure of intercellular tight junctions. Production of this toxin correlates with diarrheagenicity of V. cholerae strains in volunteers and may represent another virulence mechanism of infectious diarrhea. MATERIALS AND METHODSBacterial Strains and Growth Conditions. V. cholerae 395 is a classical Ogawa CT-positive strain that has been extensively studied in volunteer...

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Campylobacter jejuni is a zoonotic pathogen and the most common cause of bacterial foodborne diarrhoeal illness worldwide. To establish intestinal colonization prior to either a commensal or pathogenic interaction with the host, C. jejuni will encounter iron-limited niches where there is likely to be intense competition from the host and normal microbiota for iron. To gain a better understanding of iron homeostasis and the role of ferric uptake regulator (Fur) in iron acquisition in C. jejuni, a proteomic and transcriptome analysis of wild-type and fur mutant strains in iron-rich and iron-limited growth conditions was carried out. All of the proposed iron-transport systems for haemin, ferric iron and enterochelin, as well as the putative iron-transport genes p19, Cj1658, Cj0177, Cj0178 and cfrA, were expressed at higher levels in the wild-type strain under iron limitation and in the fur mutant in iron-rich conditions, suggesting that they were regulated by Fur. Genes encoding a previously uncharacterized ABC transport system (Cj1660-Cj1663) also appeared to be Fur regulated, supporting a role for these genes in iron uptake. Several promoters containing consensus Fur boxes that were identified in a previous bioinformatics search appeared not to be regulated by iron or Fur, indicating that the Fur box consensus needs experimental refinement. Binding of purified Fur to the promoters upstream of the p19, CfrA and CeuB operons was verified using an electrophoretic mobility shift assay (EMSA). These results also implicated Fur as having a role in the regulation of several genes, including fumarate hydratase, that showed decreased expression in response to iron limitation. The known PerR promoters were also derepressed in the C. jejuni Fur mutant, suggesting that they might be co-regulated in response to iron and peroxide stress. These results provide new insights into the effects of iron on metabolism and oxidative stress response as well as the regulatory role of Fur.