Variations inCampylobacter jejuniFlagellin, and Flagellin Genes, DuringIn VivoandIn VitroPassage

Active migration into the subcellular space precedes Campylobacter jejuni invasion of epithelial cells

The bacterial pathogen Campylobacter jejuni invades mucosal cells via largely undefined and rather inefficient (0.01-2 bacteria per cell) mechanisms. Here we report a novel, highly efficient C. jejuni infection pathway resulting in 10-15 intracellular bacteria per cell within 3 h of infection. Electron microscopy, pulse-chase infection assays and time-lapse multiphoton laser confocal microscopy demonstrated that the mechanism involved active and rapid migration of the pathogen into the subcellular space (termed 'subvasion'), followed by bacterial entry ('invasion') at the cell basis. Efficient subvasion was maximal after repeated rounds of selection for the subvasive phenotype. Targeted mutagenesis indicated that the CadF, JlpA or PEB1 adhesins were not required. Dissection of the selected and parental phenotypes by SDS-PAGE yielded comparable capsule polysaccharide and lipooligosaccharide profiles. Proteomics revealed reduced amounts of the chemotaxis protein CheW for the subvasive phenotype. Swarming assays confirmed that the selected phenotype exhibited altered migration behaviour. Introduction of a plasmid carrying chemotaxis genes into the subvasive strain yielded wild-type subvasion levels and migration behaviour. These results indicate that alterations in the bacterial migration machinery enable C. jejuni to actively penetrate the subcellular space and gain access to the cell interior with unprecedented efficiency.

The iron-responsive regulator Fur of Campylobacter jejuni is expressed from two separate promoters

A lacZ-based reporter gene system was used to identify the promoter of the Campylobacter jejuni iron-responsive gene regulator Fur. In other Gram-negative bacteria, the fur promoter is usually located directly upstream of the fur gene and is often autoregulated in response to iron. In this study we demonstrate that expression of the C. jejuni fur gene is controlled from two promoters located in front of the first and second open reading frames upstream of fur. Neither of these promoters was iron-regulated, and the presence of both promoters in front of fur gives higher expression of the lacZ reporter than with either promoter alone. Expression from two distal promoters might be a mechanism for regulating the level of the C. jejuni Fur protein in response to unknown stimuli.

Future research in peptic ulcer disease

For the past 10 years, research into peptic ulcer disease has focused on the surprising suggestion that gastritis and peptic ulcers may be caused by the bacterium Helicobacter pylori. However, the time has now come to reappraise research directions, as a causal link has been established, and even the most ardent sceptics now accept that H. pylori infection is the major factor in most cases of peptic ulcer disease. As with any established microbial disease, we need to understand the epidemiology and mechanisms of pathogenesis, but the major focus should be towards improving therapies and defining the long-term outcome of H. pylori eradication. To devise novel therapeutic agents effectively, we must increase our knowledge of the basic physiology of H. pylori and its ecology in the stomach. This has been a surprisingly neglected area of research and major questions remain. Why does the organism flourish in different areas of the gastric mucosa when gastric pH is increased? Is a change in pH the reason for the potentiating effects of acid-inhibitory agents on anti-H. pylori activity? Will knowledge of the host and bacterial factors that initiate ulcerogenesis allow us to better predict H. pylori-associated ulcers by using non-invasive methods? As H. pylori is a major gastroduodenal pathogen, can we eliminate the infection from selected populations? What are the criteria that will allow therapeutic intervention? The first steps have been taken in the development of an effective vaccine, but who should be immunized?(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic manipulation of Campylobacter: evaluation of natural transformation and electro-transformation

Two methods, natural transformation and electro-transformation, for the introduction of DNA into nine strains of Campylobacter jejuni were compared. Both methods were successful with a limited number of strains. Natural transformation was efficient only for the introduction of C. jejuni chromosomal DNA, while electro-transformation was also applicable for the introduction of Escherichia coli-derived vector DNA into at least one C. jejuni strain. The efficiency of DNA recombination after entry was determined using C. jejuni chromosomal DNA containing disrupted flagellin genes of C. jejuni or suicide vectors containing a portion of these genes. In the latter case, DNA recombination occurred with as little as 200-bp homology present, indicating that only short homologous DNA segments are required.