Burkholderia insulsa sp. nov., a facultatively chemolithotrophic bacterium isolated from an arsenic-rich shallow marine hydrothermal system

Enrichment cultures inoculated with hydrothermally influenced nearshore sediment from Papua New Guinea led to the isolation of an arsenic-tolerant, acidophilic, facultatively aerobic bacterial strain designated PNG-AprilT. Cells of this strain were Gram-stain-negative, rod-shaped, motile and did not form spores. Strain PNG-AprilT grew at temperatures between 4 °C and 40 °C (optimum 30–37 °C), at pH 3.5 to 8.3 (optimum pH 5–6) and in the presence of up to 2.7 % NaCl (optimum 0–1.0 %). Both arsenate and arsenite were tolerated up to concentrations of at least 0.5 mM. Metabolism in strain PNG-AprilT was strictly respiratory. Heterotrophic growth occurred with O2 or nitrate as electron acceptors, and aerobic lithoautotrophic growth was observed with thiosulfate or nitrite as electron donors. The novel isolate was capable of N2-fixation. The respiratory quinones were Q-8 and Q-7. Phylogenetically, strain PNG-AprilT belongs to the genus Burkholderia and shares the highest 16S rRNA gene sequence similarity with the type strains of Burkholderia fungorum (99.8 %), Burkholderia phytofirmans (98.8 %), Burkholderia caledonica (98.4 %) and Burkholderia sediminicola (98.4 %). Differences from these related species in several physiological characteristics (lipid composition, carbohydrate utilization, enzyme profiles) and DNA–DNA hybridization suggested the isolate represents a novel species of the genus Burkholderia , for which we propose the name Burkholderia insulsa sp. nov. The type strain is PNG-AprilT ( = DSM 28142T = LMG 28183T).

Sulfurivirga caldicuralii gen. nov., sp. nov., a novel microaerobic, thermophilic, thiosulfate-oxidizing chemolithoautotroph, isolated from a shallow marine hydrothermal system occurring in a coral reef, Japan

Novel thermophilic bacteria, designated strains VW1 and MM1T, were isolated from hydrothermal fluid and microbial mat samples, respectively, collected from a shallow marine hydrothermal system (water depth 22 m) occurring in coral reefs off Taketomi Island, Okinawa, Japan. Cells of the two novel strains were motile rods with a single polar flagellum in the exponential growth phase. In a medium that included elemental sulfur, cells of the two strains became non-motile with oval to spherical cell shapes. For both strains, growth occurred at between 30 and 60 °C (optimum temperature of 50–55 °C; 60–80 min doubling time) and between pH 5.5 and 7.1 (optimum pH 6.0). The isolates were microaerobic chemolithoautotrophs capable of using thiosulfate or tetrathionate as the sole energy source, O2 as the sole electron acceptor and CO2 as the sole carbon source. Organic substrates, such as yeast extract and tryptone, inhibited growth of both strains. The G+C contents of genomic DNA were 51.3 and 49.5 mol% for strains VW1 and MM1T, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the two strains were closely related to each other (99.9 % sequence similarity) and were distantly related to other previously described genera within the Gammaproteobacteria. The novel isolates could also be differentiated from other gammaproteobacterial genera on the basis of their physiological properties. It is suggested that the novel isolates represent the type species of a new genus, for which the name Sulfurivirga caldicuralii gen. nov., sp. nov. (type strain MM1T=JCM 13439T=DSM 17737T) is proposed.