Dissimilatory perchlorate reduction: A review

Abstract

In the United States anthropogenic activities are mainly responsible for the wide spread perchlorate contamination of drinking water, surface water, groundwater, and soil. Even at microgram levels, perchlorate causes toxicity to flora and fauna and affects growth, metabolism and reproduction in humans and animals. Reports of antithyroid effects of perchlorate and its detection in common food items have raised serious public health concerns, leading to extensive decontamination efforts in recent years. Several physico-chemical removal and biological decontamination processes are being developed. Although promising, ion exchange is a non-selective and incomplete process as it merely transfers perchlorate from water to the resin. The perchlorate-laden spent resins (perchlorate 200-500 mg L(-1)) require regeneration resulting in production of concentrated brine (6-12% NaCl) or caustic waste streams. On the contrary, biological reduction completely degrades perchlorate into O(2) and innocuous Cl(-). High reduction potential of ClO(4)(-)/Cl(-) (E° =∼ 1.28 V) and ClO(3)(-)/Cl(-) pairs (E° =1.03 V) makes these contaminants thermodynamically ideal e(-) acceptors for microbial reduction. In recent years unique dissimilatory perchlorate reducing bacteria have been isolated and detailed studies pertaining to their microbiological, biochemical, genetics and phylogenetic aspects have been undertaken which is the subject of this review article while the various physico-chemical removal and biological reduction processes have been reviewed by others.

Phenotypic and Genotypic Description of Sedimenticola selenatireducens Strain CUZ, a Marine (Per)Chlorate-Respiring Gammaproteobacterium, and Its Close Relative the Chlorate-Respiring Sedimenticola Strain NSS

“…Most PRB are capable of reducing nitrate, whereas this metabolism is rare for CRB (11,(41)(42)(43)(44). In most cases, a separate nitrate reductase exists for this metabolism, although not all strains can couple nitrate reduction to growth, nor can all strains reduce nitrate completely to nitrogen gas (31,45).…”

Transport and degradation of perchlorate in deep vadose zone: implications from direct observations during bioremediation treatment

“…To promote anaerobic conditions in the unsaturated zone, a polyethylene liner covered with soil was placed over the dripper system after its installation. Ethanol was selected as the electron donor and carbon substrate because it is a natural, soluble compound that is commonly used by perchlorate-reducing bacteria (Bardiya and Bae, 2011). Moreover, it reduces potential increase in soil salinity associated with other common sources of electron donors such as acetate (Gal et al, 2008).…”

A novel perchlorate- and nitrate-reducing bacterium, Azospira sp. PMJ

“…PCRB have been isolated from various environments and are mostly facultatively anaerobic denitrifiers (Coates and Achenbach 2004). Known PCRB belong to α-, β-, and ε-Proteobacteria, and majority of PCRB are found in the two genera of β-Proteobacteria, Dechloromonas, and Azospira (formerly Dechlorosoma) (Achenbach et al 2001; Bardiya and Bae 2011;Coates and Achenbach 2004;Coates et al 1999;Wallace et al 1996). PCRB in the genus D e c h l o ro m o n a s i s s u b d i v i d e d i n t o R C B -t y p e (Dechloromonas aromatica RCB) and CKB-type (Dechloromonas agitata CKB) based on 16S ribosomal RNA (rRNA) gene sequence (Coates and Achenbach 2004).…”