Characterization of (per)chlorate-reducing bacteria

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Chapter 1 Toxicity of chlorate and perchlorateIn plants and microorganisms, chlorate may compete with nitrate in the nitrate reductase system (van Wijk and Hutchinson, 1995).When fed to rats and mice in their drinking water, the effect of chlorate and chlorite causes oxidative damage to red blood cells, resulting in hemolytic anemia and methemoglobin formation (Condie, 1986;Gonce and Voudrias, 1994;Siddiqui, 1996; USEPA, 1999).Toxicological studies have demonstrated that perchlorate has a direct effect on iodide uptake by the thyroid gland and can result in fatal bone marrow disease (Stanbury and Wyngaarden, 1952;Achenbach et al., 2001).Therefore, the U.S.Environmental Protection Agency has put (per)chlorate on the drinking water candidate contaminant list (http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid-23292).To assure well-being of men, recent epidemiological studies recommended a maximum perchlorate contaminant level, that could result in a drinking water standard of 0.01 µM (Anonymous, 2002). Removal of chlorate and perchlorate from polluted sitesBy the use of (per)chlorate, these compounds often end up in the environment.Surface water concentrations of chlorate in the Netherlands have been reported to contain 0.38 mM in the river Meuse and 0.19 mM in the Rhine and IJssel rivers (Rosemarin et al., 1994;Versteegh et al., 1993).Chlorate and perchlorate have been detected as groundwater contaminants in the United States (USEPA, 1999).Concentrations of perchlorate in groundwater in Nevada have reached 3.7 * 10 6 µg/l, and as much as 165 µg/l has been found in water samples from Lake Mead (Gullick et al., 2001).A new ion chromatography procedure lowered the detection level to 0.04 µM which has led to the detection of perchlorate in a large number of ground water and surface water supplies (Jackson et al., 2000;Logan et al., 2001).Chlorate and perchlorate are highly soluble and chemically stable under environmental conditions (Urbansky, 1998).Removal of (per)chlorate from waste water or polluted sites is possible using different techniques.Chlorate removal from bleached effluents is possible using sulfur dioxide, but this results in an incomplete removal (Malmqvist and Welander, 1992).For removing perchlorate from drinking water, conventional water treatment technologies, such as ion exchange, carbon adsorption, have not been proven to be costefficient (Logan, 1998).Besides, these techniques produce a concentrated (per)chlorate waste that must be treated.For treatment of (per)chlorate contaminated sites and water sources, biotreatment may be recommended.Recently, removal of (per)chlorate by means of microbialWhen electrons flow from an electron donor to an electron acceptor with a more positive redox potential, free energy is released.The larger the difference between the reduction potentials of the two redox couples (∆E 0 ') the higher the free energy change.This can also be expressed as the Gibbs free energy (∆G 0 ', at pH 7 and 25ºC).The relation between ∆E 0 ' and ∆G 0 ' is written in the following equation:the number of electrons transferred F = Faraday constant (96.5 kJ * mol -1 * volt -1 ) Chapter 2 Pseudomonas chloritidismutans sp.nov., a non-denitrifying chlorate-reducing bacterium

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