McLean J, Beveridge T J
Department of Microbiology, College of Biological Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Appl Environ Microbiol. 2001 Mar;67(3):1076-84. doi: 10.1128/AEM.67.3.1076-1084.2001.
A pseudomonad (CRB5) isolated from a decommissioned wood preservation site reduced toxic chromate [Cr(VI)] to an insoluble Cr(III) precipitate under aerobic and anaerobic conditions. CRB5 tolerated up to 520 mg of Cr(VI) liter(-1) and reduced chromate in the presence of copper and arsenate. Under anaerobic conditions it also reduced Co(III) and U(VI), partially internalizing each metal. Metal precipitates were also found on the surface of the outer membrane and (sometimes) on a capsule. The results showed that chromate reduction by CRB5 was mediated by a soluble enzyme that was largely contained in the cytoplasm but also found outside of the cells. The crude reductase activity in the soluble fraction showed a K(m) of 23 mg liter(-1) (437 microM) and a V(max) of 0.98 mg of Cr h(-1) mg of protein(-1) (317 nmol min(-1) mg of protein(-1)). Minor membrane-associated Cr(VI) reduction under anaerobiosis may account for anaerobic reduction of chromate under nongrowth conditions with an organic electron donor present. Chromate reduction under both aerobic and anaerobic conditions may be a detoxification strategy for the bacterium which could be exploited to bioremediate chromate-contaminated or other toxic heavy metal-contaminated environments.
从一个已退役的木材防腐场地分离出的一株假单胞菌（CRB5），在有氧和厌氧条件下均可将有毒的铬酸盐[Cr(VI)]还原为不溶性的Cr(III)沉淀。CRB5能够耐受高达520毫克/升的Cr(VI)，并在铜和砷酸盐存在的情况下还原铬酸盐。在厌氧条件下，它还能还原Co(III)和U(VI)，并使每种金属部分内化。在外膜表面（有时）和荚膜上也发现了金属沉淀。结果表明，CRB5对铬酸盐的还原作用是由一种可溶性酶介导的，这种酶主要存在于细胞质中，但也存在于细胞外。可溶性部分的粗还原酶活性显示，其米氏常数（K(m)）为23毫克/升（437微摩尔），最大反应速度（V(max)）为0.98毫克Cr/小时·毫克蛋白质（317纳摩尔/分钟·毫克蛋白质）。在厌氧条件下，与膜相关的少量Cr(VI)还原可能解释了在存在有机电子供体的非生长条件下铬酸盐的厌氧还原。在有氧和厌氧条件下的铬酸盐还原可能是该细菌的一种解毒策略，可用于对铬酸盐污染或其他有毒重金属污染环境进行生物修复。
