High arsenic concentrations occur naturally in groundwater in some locations and can result in serious health effects when the groundwater is used as a drinking water supply. The effects have been well documented in Bangladesh, where millions of people have been exposed to unacceptably high arsenic concentrations since the 1970s and serious health impacts, such as cancer, have emerged. Here in the USA, there are several problem areas, among them, parts of Maine. In 2001, an isolate named NP4, later identified by 16S rRNA sequencing as a member of the genus Sulfurospirillum, was obtained from a contaminated well in Northport Maine. The well is among a cluster of wells with very high arsenic concentrations, and with no known anthropogenic sources of arsenic. At the time of sampling, the total arsenic concentration in the water was 1400 ppb. The presence of NP4 in groundwater, and its ability to reduce arsenate as well as a variety of other electron acceptors, including Fe(III) and Mn(IV), prompted a fluorescence in situ hybridization (FISH) study to determine its prevalence in the environment. Well water was taken from wells in the Northport area and in the Branch Lake area of Ellsworth, Maine, where the groundwater has much lower concentrations of arsenic, but with some readings still higher than the drinking water standard of 10 ppb. In the Northport area, NP4 accounted for as much as 16% of the total suspended bacterial population. While NP4 as a percentage of total bacterial numbers does not correlate with total As concentrations in groundwater, it does correlate with As(III). A positive correlation was also found between Geobacter, a genus that includes many iron-reducing bacteria, and total arsenic. These results indicate that microorganisms may be important in arsenic mobilization and speciation in groundwater.
MacRae, Jean D.
"Microbes And Arsenic Contamination Of Groundwater In Maine: Is There A Link?,"
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy:
Vol. 11, Article 8.
Available at: http://scholarworks.umass.edu/soilsproceedings/vol11/iss1/8