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= Perchlorate-Reducing Bacteria = Perchlorate-Reducing Bacteria (PRB) or Dissimilatory perchlorate-reducing bacteria (DPRB) can perform anaerobic, facultative, or microaerobic processes which result in the reduction or elimination of perchlorate, and may play a role in the remediation of perchlorate-containing pollution. Perchlorate-reducing bacteria utilize the reductase enzyme, which reduces perchlorate to chlorate, and chlorate to chlorite which are environmentally innocuous. Chlorite is rapidly removed by another enzyme, chlorite dismutase, producing molecular oxygen and chloride. Alternatively, the superoxide chlorite enzyme changes chlorite to chloride and molecular oxygen. Perchlorate degrading reactions are enhanced by electron donors such as acetate and hydrogen, and most strains of PRB can use nitrate as an electron acceptor.

Ecological Importance
Perchlorate (ClO4-) salts are ingredients in solid rocket fuels, highway safety flares, air bag inflators, fireworks, and matches. Although it is a strong oxidant, perchlorate is extremely persistent in the environment due to the high activation energy associated with its reduction. It is also highly soluble and mobile in groundwater, which can lead to widespread contamination after a release. Perchlorate-reducing bacteria, regenerable and single-pass ion exchange, reverse osmosis, and fixed-bed and fluidized-bed biological treatment can all remove perchlorate from drinking water sources.

The major toxic effect of perchlorate in humans is thyroid disruption, which can affect heart rate, mood, energy level, metabolism, bone health, and pregnancy. Perchlorate competitively inhibits the sodium-iodide symporter (NIS), an intrinsic membrane glycoprotein responsible for the uptake of iodide into the thyroid, rendering it very harmful for human health. As perchlorate levels in drinking water remain to be a growing issue, the Perchlorate Detection Limit for Purposes of Reporting (DLR) has decreased from 2 ppb to 1 ppb as of January 1, 2024.

Uses
Perchlorate reducing bacteria (PRB) play a crucial role in bioremediation efforts aimed at mitigating the environmental impact of perchlorate pollution. Given the widespread presence of perchlorate in soil, groundwater, and drinking water sources across the US, perchlorate-reducing bacteria offers a sustainable solution for treating contaminated sites and safeguarding public health. One example is the use of perchlorate reducing bacteria in wastewater treatment plants, where the bacteria is employed to remove perchlorate before discharge into the environment. Moreover, certain PRB strains, such as PRB2 and PRB4, exhibit versatile metabolic capabilities, capable of not only reducing perchlorate but also chlorate, nitrate, and nitrite, utilizing acetate as the primary electron donor.

Phylogeny
Perchlorate reducing bacteria (PRB) exhibit a phylogenetic diversity primarily within the Proteobacteria domain, spanning five genera across the Alpha-, Beta-, and Epsilonproteobacteria classes. Beta-proteobacteria represent the most common class among PRB. The evolutionary trajectory suggests recent evolution and potential horizontal transfer of perchlorate reduction genes. Unique physiological traits, such as those observed in Dechlorospirillum sp. Strain VDY, underscore the diversity within PRB. Understanding PRB phylogeny not only sheds light on their evolutionary history but also informs their ecological roles and potential applications in bioremediation. Illustrating this evolutionary journey could enhance comprehension of PRB's adaptability and ecological significance.