Relationship between rates of respiratory proton extrusion and ATP synthesis in obligately alkaliphilic Bacillus clarkii DSM 8720(T).

To elucidate the energy production mechanism of alkaliphiles, the relationship between the rate of proton extrusion via the respiratory chain and the corresponding ATP synthesis rate was examined in obligately alkaliphilic Bacillus clarkii DSM 8720(T) and neutralophilic Bacillus subtilis IAM 1026. The oxygen consumption rate of B. subtilis IAM 1026 cells at pH 7 was approximately 2.5 times higher than that of B. clarkii DSM 8720(T) cells at pH 10. The H⁺/O ratio of B. clarkii DSM 8720(T) cells was approximately 1.8 times higher than that of B. subtilis IAM 1026 cells. On the basis of oxygen consumption rate and H⁺/O ratio, the rate of proton translocation via the respiratory chain in B. subtilis IAM 1026 is expected to be approximately 1.4 times higher than that in B. clarkii DSM 8720(T). Conversely, the rate of ATP synthesis in B. clarkii DSM 8720(T) at pH 10 was approximately 7.5 times higher than that in B. subtilis IAM 1026 at pH 7. It can be predicted that the difference in rate of ATP synthesis is due to the effect of transmembrane electrical potential (Δψ) on protons translocated via the respiratory chain. The Δψ values of B. clarkii DSM 8720(T) and B. subtilis IAM 1026 were estimated as -192 mV (pH 10) and -122 mV (pH 7), respectively. It is considered that the discrepancy between the rates of proton translocation and ATP synthesis between the strains used in this study is due to the difference in ATP production efficiency per translocated proton between the two strains caused by the difference in Δψ.

Glaciecola chathamensis sp. nov., a novel marine polysaccharide-producing bacterium.

Two novel exopolysaccharide-producing bacteria, strains S18K6(T) and S18K5, were isolated from Pacific Ocean sediment. The isolates were Gram-negative, motile, strictly aerobic chemoheterotrophic bacteria. The DNA G+C contents of strains S18K6(T) and S18K5 were 44.8 and 46.3 mol%, respectively. DNA-DNA relatedness between the two strains was 70 %. Major fatty acids were hexadecanoic acid (C(16 : 0)), hexadecenoic acid (C(16 : 1)omega7c) and octadecenoic acid (C(18 : 1)omega7c). 16S rRNA gene sequence, chemotaxonomic and morphological data indicated that these strains clearly belonged to the genus Glaciecola. Based on phenotypic properties and DNA-DNA hybridization data, strains S18K6(T) and S18K5 are considered to represent a novel species of the genus Glaciecola, for which the name Glaciecola chathamensis sp. nov. is proposed. The type strain is S18K6(T) (=JCM 13645(T)=NCIMB 14146(T)).