Arsenic occurs in natural waters as arsenate and arsenite anions and is generally
considered to be toxic to biological
systems (ToxFAQs: Arsenic).
Sources of arsenic in the environment include
volcanic activity, coal burning, metal smelting, and acid mine
drainage. Organoarsenic compounds are also added to chicken feed as antibiotics.
Arsenate uptake typically occurs through phosphate transport systems, whereas
arsenite is often acquired
via aquaglyceroporins (reviewed by Rosen, 2002).
No essential biological function for arsenic has
been identified, but marine algae and
invertebrates can incorporate arsenic into complex organic molecules such as
arsenosugars and arsenobetaines (Kohlmeyer et al, 2002) and fungi and bacteria can produce volatile methylated arsenic
compounds (reviewed by Bentley and Chasteen, 2002).
Both microbial arsenate reduction and arsenite oxidation are well documented as detoxification mechanisms (reviewed by Mukhopadhyay et al, 2002). Additionally, some prokaryotes can use arsenate as a
terminal electron acceptor during anaerobic growth and others can utilize arsenite as an electron donor to
generate energy (reviewed by Oremland and Stoltz, 2003). In a Shewanella sp., respiratory arsenate reduction
and detoxifying arsenate reduction were found to be mediated by separate systems (Saltikov and Newman, 2003).
For more information:
Medline for arsenic metabolism AND bacteria
Salmassi TM, et al. Oxidation of Arsenite by Agrobacterium albertimagni, AOL15, sp. nov., Isolated from Hot Creek,
Geomicrobiology J. 2002;19:53-66.
Niggemyer A, Spring S, Stackebrandt E, Rosenzweig RF. Isolation
and characterization of a novel As(V)-reducing bacterium:
implications for arsenic mobilization and the genus
Appl Environ Microbiol. 2001 Dec;67(12):5568-80.
Tamas MJ, Wysocki R. Mechanisms involved in metalloid transport
and tolerance acquisition. Curr Genet. 2001;40:2-12.