Genomic-sequence comparison of two unrelated isolates of the human gastric pathogen Helicobacter pylori.

Helicobacter pylori, one of the most common bacterial pathogens of humans, colonizes the gastric mucosa, where it appears to persist throughout the host's life unless the patient is treated. Colonization induces chronic gastric inflammation which can progress to a variety of diseases, ranging in severity from superficial gastritis and peptic ulcer to gastric cancer and mucosal-associated lymphoma. Strain-specific genetic diversity has been proposed to be involved in the organism's ability to cause different diseases or even be beneficial to the infected host and to participate in the lifelong chronicity of infection. Here we compare the complete genomic sequences of two unrelated H. pylori isolates. This is, to our knowledge, the first such genomic comparison. H. pylori was believed to exhibit a large degree of genomic and allelic diversity, but we find that the overall genomic organization, gene order and predicted proteomes (sets of proteins encoded by the genomes) of the two strains are quite similar. Between 6 to 7% of the genes are specific to each strain, with almost half of these genes being clustered in a single hypervariable region.

Partial characterization of a Candida albicans fimbrial adhesin.

Candida albicans is the primary etiologic agent of candidiasis, a disease that can vary from superficial mucosal lesions to life-threatening systemic or disseminated diseases. Strains of C. albicans have been reported to possess long, thin filamentous protein cell surface appendages termed fimbriae (R.B. Gardiner, M. Canton, and A. W. Day, Bot. Gaz. 143:534-541, 1982). These fimbriae were isolated, purified, and partially characterized. The major structural subunit of the fimbriae is a glycoprotein which consists of 80 to 85% carbohydrate (consisting primarily of D-mannose) and 10 to 15% protein. The molecular weight of the glycosylated fimbrial subunit is approximately 66,000, while unglycosylated protein has an approximate molecular weight of 8,644. The fimbriae function as adhesins mediating C. albicans binding to human buccal epithelial cells. Amino acid analysis of the purified fimbrial subunit indicates that the fimbrial subunit is composed of 50% hydrophobic amino acid residues. The N terminus of the fimbrial subunit is blocked to N-terminal sequencing.

Thin, aggregative fimbriae mediate binding of Salmonella enteritidis to fibronectin.

The binding of human fibronectin and Congo red by an autoaggregative Salmonella enteritidis strain was found to be dependent on its ability to produce thin, aggregative fimbriae, named SEF 17 (for Salmonella enteritidis fimbriae with an apparent fimbrin molecular mass of 17 kDa). Two other fimbrial types produced by S. enteritidis, SEF 14 and SEF 21, were not responsible for the aggregative phenotype or for fibronectin binding. SEF 17-negative TnphoA mutants which retained the ability to produce SEF 14 and SEF 21 were unable to bind human fibronectin or Congo red and lost the ability to autoaggregate. Only purified SEF 17 but not purified SEF 14 or SEF 21 bound fibronectin in a solid-phase binding assay. Furthermore, only SEF 17 was able to inhibit fibronectin binding to S. enteritidis whole cells in a direct competition enzyme-linked immunosorbent assay. These results indicate that SEF 17 are the fimbriae responsible for binding fibronectin by this enteropathogen.