A novel moderately thermophilic, organotrophic, microaerophilic, facultatively chemolithotrophic bacterium, designated strain 506 T, was isolated from a deep-sea hydrothermal vent site at 13degreesN in the East Pacific Rise. Cells were Gram-negative, non-motile rods. The organism grew in the temperature range 40-68degreesC, with an optimum at 60degreesC, and in the pH range 5.5-8.4, with an optimum around pH 7.5. The NaCl concentration for growth was in the range 10-50 g l(-1), with an optimum at 30 g l(-1). Strain 506 T grew chemoorganoheterotrophically with carbohydrates, proteinaceous substrates, organic acids and alcohols using oxygen or nitrate as electron acceptor. Alternatively, strain 506(T) was able to grow lithoheterotrophically w...