Novel autotrophic arsenite-oxidizing bacteria isolated from soil and sediments

Abstract

Arsenic oxidation is recognized as being mediated by both heterotrophic and chemoautotrophic microorganisms. Enrichment cultures were established to determine whether chemoautotrophic microorganisms capable of oxidizing arsenite As(III) to arsenate As(V) are present in selected contaminated but nonextreme environments. Three new organisms, designated as strains OL-1, S-1 and CL-3, were isolated and found to oxidize 10 mM arsenite to arsenate under aerobic conditions using CO2-bicarbonate (CO2/HCO3-) as a carbon source. Based on 16S rRNA gene sequence analyses, strain OL-1 was 99% most closely related to the genus Ancylobacter, strain S-1 was 99% related to Thiobacillus and strain CL-3 was 98% related to the genus Hydrogenophaga. The isolates are facultative autotrophs and growth of isolated strains on different inorganic electron donors other than arsenite showed that all three had a strong preference for several sulfur species, while CL-3 was also able to grow on ammonium and nitrite. The RuBisCO Type I (cbbL) gene was positively amplified and sequenced in strain CL-3, and the Type II (cbbM) gene was detected in strains OL-1 and S-1, supporting the autotrophic nature of the organisms.

Arsenite Oxidation in Ancylobacter dichloromethanicus As3-1b Strain: Detection of Genes Involved in Arsenite Oxidation and CO2 Fixation

“…Ancylobacter dichloromethanicus strain As3-1b can be considered as facultative chemolithotroph being able to grow either chemolithotrophically or chemoorganotrophically, similarly to the previously identified As(III)-oxidizers [10,18,20,25]. The isolation of A. dichloromethanicus As3-1b from an agricultural As-polluted soil strengthens the finding that chemolithotrophic As(III) oxidizing bacteria are not restricted to extreme environments [8,11,12,20], in accordance with Garcia-Dominguez et al [10].…”

“…For numerous bacterial strains (heterotrophic arsenite-oxidizers), the oxidation of As(III) is considered a detoxification mechanism, even if in these bacteria, As(III) may be used as a supplemental energy source [3]. In contrast, certain strains are able to use arsenite as the source of energy and reducing power (chemolithotrophic arsenite-oxidizers) to grow in the presence of carbon dioxide under both aerobic [4,9,10,25] and nitrate-reducing [20] conditions. CO 2 fixation in chemolithotrophic bacteria generally occurs through the Calvin-Benson-Bassham cycle mediated by ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), which occurs in ecologically and evolutionary diverse organisms from all domains of life.…”

Functions and Unique Diversity of Genes and Microorganisms Involved in Arsenite Oxidation from the Tailings of a Realgar Mine

“…In general, most of the autotrophic oxidizers tend to be members of Alphaproteobacteria and the heterotrophic strains belong to Betaproteobacteria (22,24). Consistent with this observation, all of the four chemoautotrophic arsenite-oxidizing strains isolated from the tailings belong to Alphaproteobacteria.…”

“…Many bacteria are also able to reduce arsenate as a means of detoxification using ArsC, an arsenate reductase that is capable of converting intracellular arsenate into arsenite, which is further transported out of the cell by an energy-dependent efflux process (14-16). Arsenite-oxidizing bacteria (AOB) can oxidize As(III) into As(V) under aerobic or anaerobic conditions (17)(18)(19)(20)(21)(22)(23)(24)(25). Under aerobic conditions, AOB are able to convert As(III) into As(V) by using As(III) as an electron donor and oxygen as an electron acceptor (19-23); under anaerobic conditions, some AOB can convert As(III) into As(V) by using As(III) as an electron donor and nitrate, selenate, or chlorate as an electron acceptor (18,(24)(25)(26)(27).…”

“…Arsenite-oxidizing bacteria (AOB) can oxidize As(III) into As(V) under aerobic or anaerobic conditions (17)(18)(19)(20)(21)(22)(23)(24)(25). Under aerobic conditions, AOB are able to convert As(III) into As(V) by using As(III) as an electron donor and oxygen as an electron acceptor (19)(20)(21)(22)(23); under anaerobic conditions, some AOB can convert As(III) into As(V) by using As(III) as an electron donor and nitrate, selenate, or chlorate as an electron acceptor (18,(24)(25)(26)(27). AOB are either chemoautotrophic, using carbon dioxide as the sole carbon source, or heterotrophic, using organic carbon as the sole carbon source.…”