Redox transformations of arsenic oxyanions in periphyton communities

Applied and Environmental Microbiology
By: , and 



Periphyton (Cladophora sp.) samples from a suburban stream lacking detectable dissolved As were able to reduce added As(V) to As(III) when incubated under anoxic conditions and, conversely, oxidized added As(III) to As(V) with aerobic incubation. Both types of activity were abolished in autoclaved controls, thereby demonstrating its biological nature. The reduction of As(V) was inhibited by chloramphenicol, indicating that it required the synthesis of new protein. Nitrate also inhibited As(V) reduction, primarily because it served as a preferred electron acceptor to which the periphyton community was already adapted. However, part of the inhibition was also caused by microbial reoxidation of As(III) linked to nitrate. Addition of [14C]glucose to anoxic samples resulted in the production of 14CO2, suggesting that the observed As(V) reduction was a respiratory process coupled to the oxidation of organic matter. The population density of As(V)-reducing bacteria within the periphyton increased with time and with the amount of As(V) added, reaching values as high as ∼106 cells ml−1 at the end of the incubation. This indicated that dissimilatory As(V) reduction in these populations was linked to growth. However, As(V)-respiring bacteria were found to be present, albeit at lower numbers (∼102 ml−1), in freshly sampled periphyton. These results demonstrate the presence of a bacterial population within the periphyton communities that is capable of two key arsenic redox transformations that were previously studied in As-contaminated environments, which suggests that these processes are widely distributed in nature. This assumption was reinforced by experiments with estuarine samples of Cladophora sericea in which we detected a similar capacity for anaerobic As(V) reduction and aerobic As(III) oxidation.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Redox transformations of arsenic oxyanions in periphyton communities
Series title Applied and Environmental Microbiology
DOI 10.1128/AEM.70.11.6428-6434.2004
Volume 70
Issue 11
Year Published 2004
Language English
Publisher ASM
Contributing office(s) Toxic Substances Hydrology Program
Description 7 p.
First page 6428
Last page 6434
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