Isolation and characterization of NP4, arsenate-reducing Sulfurospirillum, from Maine groundwater

Parts of New England have naturally high arsenic concentrations in groundwater. High arsenic correlates broadly with bedrock type, but levels are patchy, so other conditions must affect arsenic mobilization. Microorganisms capable of arsenate (As(V)) respiration, if present, could affect arsenic speciation and mobility in groundwater. An arsenate-reducing bacterium, designated NP4, was isolated from groundwater obtained from a well in Northport, Me., with extremely high (> 1,400 mu g L-1) arsenic. Sequencing of the 16S rDNA showed that NP4 groups with the Sulfurospirillum genus. It can grow using arsenate, nitrate, iron(III), selenate, manganese(IV), sulfite, sulfur or thiosulfate as terminal electron acceptors and lactate, formate and pyruvate as electron donors. It can also grow on fumarate or lactate alone. This Sulfurospirillum isolate is distinct from other members of the genus in its carbon and electron acceptor usage. The activity of this type of microorganism could negatively affect groundwater quality by converting As(V) to the more toxic and difficult to remove As(III) form.