Isolation of Arsenite-Oxidizing Bacteria from Arsenic-Enriched Sediments from Camarones River, Northern Chile

Abstract

In Northern Chile, high arsenic concentrations are found in natural water, both natural and anthropogenic sources, a significant health risk. Nine bacterial strains were isolated from Camarones river sediments, located in Northern Chile, a river showing arsenic concentrations up to 1,100 microg/L. These strains were identified as Pseudomonas and they can oxidize arsenite (As(III)) to the less mobile arsenate (As(V)). The arsenite oxidase genes were identified in eight out of nine isolates. The arsenite oxidizing ability shown by the nine strains isolated from arsenic enriched sediments open the way to their potential application in biological treatment of effluents contaminated with arsenic.

Unsuspected Diversity of Arsenite-Oxidizing Bacteria as Revealed by Widespread Distribution of theaoxBGene in Prokaryotes

“…The aerobic arsenite oxidases involved in such processes are heterodimers consisting of a large subunit with a molybdenum center and a [3Fe-4S] cluster (AroA, AsoA, and AoxB) and a small subunit containing a Rieske-type [2Fe-2S] cluster (AroB, AsoB, and AoxA) (1, 13). The large subunit in these enzymes is similar to that found in other members of the dimethyl sulfoxide (DMSO) reductase family of molybdenum enzymes but is clearly phylogenetically divergent from the respiratory arsenate reductases (ArrA) or other proteins of the DMSO reductase family of molybdenum oxidoreductases, such as the new arsenite reductase described recently for Alkalilimnicola ehrlichii (25,31,40).aox genes have been identified in 25 bacterial and archaeal genera isolated from various arsenic-rich environments, most of which belong to the Alpha-, Beta-, or Gammaproteobacteria phylum (7,10,12,14,23,25,29,32,37). Recent studies based on environmental DNA extracted from soils, sediments, and geothermal mats with different chemical characteristics and various levels of arsenic contamination have suggested that the distribution and the diversity of arsenite-oxidizing microorganisms may be greater than previously suggested (6, 10, 14-16, 18, 28, 29).…”

“…aox genes have been identified in 25 bacterial and archaeal genera isolated from various arsenic-rich environments, most of which belong to the Alpha-, Beta-, or Gammaproteobacteria phylum (7,10,12,14,23,25,29,32,37). Recent studies based on environmental DNA extracted from soils, sediments, and geothermal mats with different chemical characteristics and various levels of arsenic contamination have suggested that the distribution and the diversity of arsenite-oxidizing microorganisms may be greater than previously suggested (6, 10, 14-16, 18, 28, 29).…”

Natural Arsenic in Global Groundwaters: Distribution and Geochemical Triggers for Mobilization

“…Three types of clay minerals have been used successfully to oxidize As(III), suggesting that the oxidation and adsorption of produced As(V) occur on the surface of clay minerals [101]. Moreover, the oxidation of trivalent As is found to be catalyzed by some microorganisms, including Pseudomonas arsenitoxidans, Alcaligenes faecalis, Cenibacterium arsenoxidans, Thermus sp., Thermus thermophilus, and Agrobacterium tumefaciens, using oxygen as the terminal electron acceptor [31,94,102,103]. Bacteria species attached to submerged macrophytes in a stream near geothermal sources are reported to be capable of mediating the rapid oxidation of As(III) [104], and the oxidation reaction may be expressed as follows [95]:…”

Bioprospecting arsenite oxidizing bacteria in the soil of the Comarca Lagunera

“…This metalloid occurs in different oxidation states: arsenate As (V), arsenite As (III), elemental As (0) and arsenide As (-III) (Tsai, Singh, & Chen, 2009). Arsenite is more toxic than arsenate, which is poorly soluble in water and is therefore less bioavailable (Valenzuela, Campos, Yañez, Zarror, & Mondaca, 2009). When there is a greater natural geological presence of arsenic, it is possible to find high levels of the element in groundwater, as is the case with Bangladesh, India, China, Taiwan, Mongolia, Chile, Argentina, Mexico and many places in the United States (Anawar et al, 2003;Campos, Valenzuela, Alcorta, Escalante, & Mondaca, 2007).…”