Campylobacter jejuni is the main cause of bacterial acute gastroenteritis worldwide. In its colonization of the host intestinal tract, it encounters secreted mucins in the mucus layer and surface mucins in the epithelial cells. Mucins are complex glycoproteins that comprise the major component of mucus and give mucus its viscous consistency. MUC2 is the most abundant secreted mucin in the human intestine; it is a major chemoattractant for C. jejuni, and the bacterium binds to it. There are no studies on the transcriptional response of the bacterium to this mucin. Here, cell-culture techniques and quantitative RT-PCR were used to characterize in vitro the effects of MUC2 on C. jejuni growth and the changes in expression of 20 C. jejuni genes related to various functions. The genes encoding cytolethal distending toxin protein (cdtABC), vacuolating cytotoxin (vacB), C. jejuni lipoprotein (jlpA), Campylobacter invasion antigen (ciaB), the multidrug efflux system (cmeAB), putative mucin-degrading enzymes (cj1344c, cj0843c, cj0256 and cj1055c), flagellin A (flaA) and putative rod-shape-determining proteins (mreB and mreC) were upregulated, whereas those encoding Campylobacter adhesion fibronectin-binding protein (cadF) and sialic acid synthase (neuB1) were downregulated. These results showed that C. jejuni utilizes MUC2 as an environmental cue for the modulation of expression of genes with various functions including colonization and pathogenicity. INTRODUCTIONCampylobacter jejuni is a Gram-negative, spiral, motile bacterium that colonizes the intestine of vertebrates. The bacterium is the main cause of human acute bacterial gastroenteritis in both developing and developed countries (Allos, 2001). Common symptoms of human C. jejuni infection are diarrhoea, fever, vomiting and abdominal pain. C. jejuni infection is a leading cause of childhood morbidity and mortality in the developing world (Allos, 2001). It is associated with the development of intestinal mucosa-associated lymphoid tissue lymphoma (Lecuit et al., 2004) and with post-infection autoimmune diseases such as Guillain-Barré and Miller Fisher syndromes (Yuki & Koga, 2006). Its various pathogenic effects indicate that C. jejuni infection poses a significant global public health problem.The mucosal tissues of the gastrointestinal, respiratory, urinary and reproductive tracts, as well as the surfaces of several organs such as the eye, nose and mouth, are exposed to the external environment. The mucus layer present in these tissues provides protection to underlying mucosal epithelial cells against chemical, enzymic, microbial and mechanical insult (Neutra & Forstner, 1987;Strugala et al., 2003). The major components of the mucus layer are secreted gel-forming mucins, complex glycoproteins that give mucus its viscous consistency.Most pathogenic bacteria that colonize the gastrointestinal tract subvert the mucus barrier by effective motility through the gel and the use of enzymes capable of degrading mucin carbohydrates and/or mucins. MUC2 is the most common gel-f...

Helicobacter pylori infection is one of the most common chronic bacterial infections in humans. The association of other Helicobacter spp. with extragastric diseases in animals is well established, and a role of these bacteria in human liver disease is becoming clearer. Several case-control studies have reported possible associations of Helicobacter spp. with various liver diseases, including hepatocellular carcinoma, which is the fifth most common type of carcinoma among men worldwide, and the eighth most common among women. Thus, it is important to understand molecular mechanisms that may lead to hepatotoxicity or hepatocellular dysfunction in which Helicobacter spp. may play a role in inducing malignant transformation of liver cells.

The bacterium Wolinella succinogenes is the only known species of its genus. It was first isolated from cow ruminal fluid, and in cattle, it dwells in the reticulum and rumen compartments of the stomach. The global protein response of W. succinogenes to ox-bile was investigated with the aim to understand bile-tolerance mechanisms of the bacterium. Bacteria were grown in liquid media supplemented with different bile concentrations to determine its effects on growth and morphology. Proteomic analyses served to identify 14 proteins whose expression was modulated by the presence of 0.2% bile. Quantitative real-time PCR analyses of the expression of selected genes were employed to obtain independent confirmation of the proteomics data. Proteins differentially expressed revealed metabolic pathways involved in the adaptation of W. succinogenes to bile. The data suggested that bile stress elicited complex physiological responses rather than just specific pathways, and identified proteins previously unknown to be involved in the adaptation of bacteria to bile.