An extracellular [NiFe] hydrogenase mediating iron corrosion is encoded in a genetically unstable genomic island in Methanococcus maripaludis.

Certain methanogens deteriorate steel surfaces through a process called microbiologically influenced corrosion (MIC). However, the mechanisms of MIC, whereby methanogens oxidize zerovalent iron (Fe0), are largely unknown. In this study, Fe0-corroding Methanococcus maripaludis strain OS7 and its derivative (strain OS7mut1) defective in Fe0-corroding activity were isolated. Genomic analysis of these strains demonstrated that the strain OS7mut1 contained a 12-kb chromosomal deletion. The deleted region, termed "MIC island", encoded the genes for the large and small subunits of a [NiFe] hydrogenase, the TatA/TatC genes necessary for the secretion of the [NiFe] hydrogenase, and a gene for the hydrogenase maturation protease. Thus, the [NiFe] hydrogenase may be secreted outside the cytoplasmic membrane, where the [NiFe] hydrogenase can make direct contact with Fe0, and oxidize it, generating hydrogen gas: Fe0 + 2 H+ → Fe2+ + H2. Comparative analysis of extracellular and intracellular proteomes of strain OS7 supported this hypothesis. The identification of the MIC genes enables the development of molecular tools to monitor epidemiology, and to perform surveillance and risk assessment of MIC-inducing M. maripaludis.

Prevalence of esophageal candidiasis among patients treated with inhaled fluticasone propionate.

OBJECTIVES: Development of oropharyngeal candidiasis is a frequently reported adverse effect of inhaled corticosteroid use, but the prevalence of esophageal candidiasis is unknown. The aim of this study was to estimate the prevalence of esophageal candidiasis among patients treated with an inhaled corticosteroid, fluticasone propionate. METHODS: Upper GI endoscopy was performed on 49 patients treated with inhaled fluticasone propionate to examine the prevalence of esophageal candidiasis. Of the patients, 36 had bronchial asthma and 13 had chronic obstructive pulmonary disease. To compare the prevalence with control patients, upper GI endoscopy was performed on 700 consecutive patients without malignancy or immunosuppression. RESULTS: The prevalence of esophageal candidiasis was 37% among patients treated with inhaled fluticasone propionate, whereas only 0.3% of the control patients had the infection. The prevalence was especially high among patients with diabetes mellitus or those who were treated with a high dose of inhaled fluticasone propionate. Moreover, a reduction in the daily dose of inhaled fluticasone propionate eliminated the infection in four of five patients. CONCLUSIONS: Esophageal candidiasis is a common complication of inhaled corticosteroid use.