Isolation of Tellurite- and Selenite-Resistant Bacteria from Hydrothermal Vents of the Juan de Fuca Ridge in the

Deep-ocean hydrothermal-vent environments are rich in heavy metals and metalloids and present excellent sites for the isolation of metal-resistant microorganisms. Both metalloid-oxide-resistant and metalloid-oxidereducing bacteria were found. Tellurite- and selenite-reducing strains were isolated in high numbers from ocean water near hydrothermal vents, bacterial films, and sulfide-rich rocks. Growth of these isolates in media containing K2TeO3 or Na2SeO3 resulted in the accumulation of metallic tellurium or selenium. The MIC of K2TeO3 ranged from 1,500 to greater than 2,500 g/ml, and the MIC of Na2SeO3 ranged from 6,000 to greater than 7,000 g/ml for 10 strains. Phylogenetic analysis of 4 of these 10 strains revealed that they form a branch closely related to members of the genus Pseudoalteromonas, within the -3 subclass of the Proteobacteria. All 10 strains were found to be salt tolerant, pH tolerant, and thermotolerant. The metalloid resistance and morphological, physiological, and phylogenetic characteristics of newly isolated strains are described. Selenium (Se), a naturally occurring element, is essential for biological systems at low concentrations and toxic at higher levels. Under aerobic conditions Se is present in several redox forms, including the elemental form Se; however, it exists predominantly in the high-valence toxic and soluble forms selenate (Se VI O4 2 ) and selenite (Se IV O3 2 ) (4). The roles of