Magnetovibrio blakemorei gen. nov., sp. nov., a magnetotactic bacterium (Alphaproteobacteria: Rhodospirillaceae) isolated from a salt marsh.

A magnetotactic bacterium, designated strain MV-1(T), was isolated from sulfide-rich sediments in a salt marsh near Boston, MA, USA. Cells of strain MV-1(T) were Gram-negative, and vibrioid to helicoid in morphology. Cells were motile by means of a single polar flagellum. The cells appeared to display a transitional state between axial and polar magnetotaxis: cells swam in both directions, but generally had longer excursions in one direction than the other. Cells possessed a single chain of magnetosomes containing truncated hexaoctahedral crystals of magnetite, positioned along the long axis of the cell. Strain MV-1(T) was a microaerophile that was also capable of anaerobic growth on some nitrogen oxides. Salinities greater than 10 % seawater were required for growth. Strain MV-1(T) exhibited chemolithoautotrophic growth on thiosulfate and sulfide with oxygen as the terminal electron acceptor (microaerobic growth) and on thiosulfate using nitrous oxide (N2O) as the terminal electron acceptor (anaerobic growth). Chemo-organoautotrophic and methylotrophic growth was supported by formate under microaerobic conditions. Autotrophic growth occurred via the Calvin-Benson-Bassham cycle. Chemo-organoheterotrophic growth was supported by various organic acids and amino acids, under microaerobic and anaerobic conditions. Optimal growth occurred at pH 7.0 and 26-28 °C. The genome of strain MV-1(T) consisted of a single, circular chromosome, about 3.7 Mb in size, with a G+C content of 52.9-53.5 mol%.Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain MV-1(T) belongs to the family Rhodospirillaceae within the Alphaproteobacteria, but is not closely related to the genus Magnetospirillum. The name Magnetovibrio blakemorei gen. nov., sp. nov. is proposed for strain MV-1(T). The type strain of Magnetovibrio blakemorei is MV-1(T) ( = ATCC BAA-1436(T)  = DSM 18854(T)).