Santini, JM; Stolz, JF; Macy, JM
A new strictly anaerobic arsenate-respiring bacterium has been isolated from arsenic-contaminated mud obtained from a gold mine in Bendigo, Australia. This organism, designated JMM-4, was found to be a Gram-positive, spore-forming rod, 0.6 x 2.5-3 mum, motile by means of flagella that are subpolar or along one side of the cell. JMM-4 grows using arsenate as the terminal electron acceptor and lactate as the electron donor. Arsenate is reduced to arsenite and the lactate is oxidized to CO2 via the intermediate, acetate. The doubling time for exponential growth with arsenate (5 mM) and lactate (5 mM) was 4.3 +/- 0.2 h. Alternative electron donors used by JMM-4 when grown with arsenate as the terminal electron acceptor are acetate, pyruvate, succinate, malate, glutamate, and hydrogen (with acetate as carbon source). Apart from arsenate, nitrate can serve as an alternative electron acceptor. Optimal growth occurs at pH 7.8 with a sodium chloride concentration of 1.2 g . l(1). Based upon 16S rRNA gene sequence analysis, JMM-4 falls within the low G+C, Gram-positive, aerobic, spore-forming bacilli cluster and is most closely related to the previously described haloalkalophilic arsenate/selenate respiring-bacterium Bacillus arsenicoselenatis. The physiological differences between JMM-4 and B. arsenicoselenatis however suggest that JMM-4 is a new species of Bacillus.