Chlorate Metabolism in Pure Cultures of Escherichia coli O157:H7 Pretreated with either Nitrate or Chlorate

Abstract

Previous research has suggested that nitrate-respiring pathogens such as Escherichia coli O157:H7 and Salmonella spp. are susceptible to chlorate salts due to the conversion of chlorate to chlorite by respiratory nitrate reductase. This study was conducted to determine the effect of chlorate on E. coli O157:H7 growth and chlorate biotransformation and to determine whether chlorite is produced in anaerobic culture of E. coli O157:H7. Final concentrations of E. coli O157:H7 were generally decreased by about 2 log units in incubations containing > or =5 mM chlorate, except when bacteria were pretreated with 10 mM chlorate. [(36)Cl]Chlorate metabolism by pure cultures of E. coli O157:H7 was not measurable above chlorate concentrations of 5 mM, but measurable chlorate reduction occurred in cultures containing 0.5, 1, or 5 mM [(36)Cl]chlorate. Pretreatment of E. coli O157:H7 with 5 mM nitrate did not increase the rate of chlorate conversion to chloride, suggesting that nitrate did not induce nitrate reductase isoforms capable of metabolizing chlorate in E. coli O157:H7. Pure cultures of E. coli O157:H7 preconditioned with 10 mM chlorate had an attenuated ability to transform [(36)Cl]chlorate to [(36)Cl]chloride with measurable chlorate reduction only occurring in 0.5 mM chlorate treatments. The hypothesis that E. coli O157:H7 is sensitive to chlorate by virtue of the reduction of chlorate to chlorite ion (ClO(2)(-)) was supported, but not proven, by the direct measurement of low concentrations of [(36)Cl]ClO(2)(-) in incubation media containing 0.5 mM [(36)Cl]ClO(3)(-). Collectively these results indicate that growth of E. coli O157:H7 in pure culture will be reduced in the presence of 5 mM or greater concentrations of sodium chlorate and that E. coli O157:H7 is capable of producing chlorite ions during the metabolism of chlorate.

Discovering the Importance of ClO• in a Coupled Electrochemical System for the Simultaneous Removal of Carbon and Nitrogen from Secondary Coking Wastewater Effluent

“…This result is consistent with the extent of contaminant mineralization observed with the remarkable decay in the TOC value during the longer electrolysis time (Figure S4). Note that the 6 h of treatment did not induce appreciably decreased toxicity compared with the untreated wastewater, possibly due to the presence of chlorate (Figure S2), which has been proven to be toxic to E. coli …”

“…Note that the 6 h of treatment did not induce appreciably decreased toxicity compared with the untreated wastewater, possibly due to the presence of chlorate (Figure S2), which has been proven to be toxic to E. coli. 42 Identification of the Predominant ClO • Radical and Elucidation of Its Role in Pollutant Removal. The EPR tests (with DMPO as the spin-trapping agent) were conducted to qualitatively identify the reactive radicals available in the coupled electrochemical system, as depicted in Figure 4a.…”

Effect of intravenous or oral sodium chlorate administration on the fecal shedding of Escherichia coli in sheep1,2

“…That is, nitrate reductase, which normally converts nitrate to nitrite under anaerobic conditions, may co-metabolize chlorate (ClO 3 -) to chlorite (ClO 2 -; Pichinoty et al, 1969;Stewart, 1988). Chlorite is considered to be the ultimate toxin in exposed bacteria and it has been indirectly (Pichinoty et al, 1969) and directly (Goksøyr, 1952;Smith et al, 2009) measured in cultures of chlorate exposed bacteria. Although aerobes and anaerobes may produce a number of nitrate reductases, only the membrane bound nitrate reductases are believed to metabolize chlorate (Bell et al, 1990(Bell et al, , 1993.…”

Distribution, Identification, and Quantification of Residues after Treatment of Ready-To-Eat Salami with 36Cl-Labeled or Nonlabeled Chlorine Dioxide Gas

“…Additionally, Smith et al were unable to recover any 36 Cl-chlorite residue after direct administration of >100 μg/g sodium 36 Cl-chlorite into tomatoes, indicating that chlorite is unstable, at least in tomato matrix. In contrast, Smith et al were able to detect the transient formation of 36 Cl-chlorite from 36 Cl-chlorate in pure cultures of Escherichia coli. Furthermore, chlorite residues were not measurable after treatment of tomatoes or cantaloupe , with 36 Cl-labeled chlorine dioxide gas.…”