Strain DVT, a halotolerant, Gram-negative, facultatively anaerobic bacterium, was isolated from a hypersaline pond located in Death Valley, California. The cells were non-spore-forming, motile, curved rods (1.0-1.8 x 0.5-0.6 microns) and occurred singly, in pairs or rarely in chains. Strain DVT was oxidase-, catalase-, Voges-Proskauer-, amylase-, gelatinase- and lipase-positive and indole-negative. Nitrate, sulfate and fumarate were not used as electron acceptors. Carbohydrates served as energy sources both aerobically and anaerobically. Strain DVT grew optimally at 37 degrees C (temperature range 20-50 degrees C) with 2.5% NaCl (NaCl range 0-12.5%) and pH 7.3 (pH range of 5.5-8.5) in a glucose/yeast extract medium with a doubling time of 20 min (aerobically) or 41 min (anaerobically). The end products of glucose fermentation were ethanol, isobutyrate, propionate, lactate, formate and CO2. Strain DVT was resistant to penicillin, D-cycloserine, streptomycin and tetracycline (200 micrograms ml-1). The G + C content was 50 mol%. 16S rRNA gene sequence analysis indicated that it was closely related to Salinivibrio costicola (97.7%) and this was confirmed by DNA-DNA hybridization (93% relatedness). However, phenotypic characteristics such as halotolerance, gas production, growth at 50 degrees C, antibiotic resistance, sugar-utilization spectrum and phylogenetic signatures are sufficiently different from Salinivibrio costicola to warrant designating strain DVT as a new subspecies of Salinivibrio costicola, Salinivibrio costicola subsp. vallismortis subsp. nov. (= DSM 8285T).