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^Tconsisted 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 Rhodospirillaceaewithin the Alphaproteobacteria, but is not closely related to the genusMagnetospirillum. 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).