Oremland R S, Blum J S, Bindi A B, Dowdle P R, Herbel M, Stolz J F
U.S. Geological Survey, Menlo Park, California 94025, USA.
Appl Environ Microbiol. 1999 Oct;65(10):4385-92. doi: 10.1128/AEM.65.10.4385-4392.1999.
Washed-cell suspensions of Sulfurospirillum barnesii reduced selenate [Se(VI)] when cells were cultured with nitrate, thiosulfate, arsenate, or fumarate as the electron acceptor. When the concentration of the electron donor was limiting, Se(VI) reduction in whole cells was approximately fourfold greater in Se(VI)-grown cells than was observed in nitrate-grown cells; correspondingly, nitrate reduction was approximately 11-fold higher in nitrate-grown cells than in Se(VI)-grown cells. However, a simultaneous reduction of nitrate and Se(VI) was observed in both cases. At nonlimiting electron donor concentrations, nitrate-grown cells suspended with equimolar nitrate and selenate achieved a complete reductive removal of nitrogen and selenium oxyanions, with the bulk of nitrate reduction preceding that of selenate reduction. Chloramphenicol did not inhibit these reductions. The Se(VI)-respiring haloalkaliphile Bacillus arsenicoselenatis gave similar results, but its Se(VI) reductase was not constitutive in nitrate-grown cells. No reduction of Se(VI) was noted for Bacillus selenitireducens, which respires selenite. The results of kinetic experiments with cell membrane preparations of S. barnesii suggest the presence of constitutive selenate and nitrate reduction, as well as an inducible, high-affinity nitrate reductase in nitrate-grown cells which also has a low affinity for selenate. The simultaneous reduction of micromolar Se(VI) in the presence of millimolar nitrate indicates that these organisms may have a functional use in bioremediating nitrate-rich, seleniferous agricultural wastewaters. Results with (75)Se-selenate tracer show that these organisms can lower ambient Se(VI) concentrations to levels in compliance with new regulations proposed for release of selenium oxyanions into the environment.
当巴恩斯硫螺旋菌的洗细胞悬液与硝酸盐、硫代硫酸盐、砷酸盐或富马酸盐作为电子受体一起培养时，能还原硒酸盐[Se(VI)]。当电子供体浓度受到限制时，与在硝酸盐培养的细胞中观察到的情况相比，在以Se(VI)培养的细胞中全细胞的Se(VI)还原率大约高四倍；相应地，在硝酸盐培养的细胞中硝酸盐还原率比在Se(VI)培养的细胞中大约高11倍。然而，在这两种情况下都观察到了硝酸盐和Se(VI)的同时还原。在非限制电子供体浓度下，悬浮有等摩尔硝酸盐和硒酸盐的硝酸盐培养细胞实现了氮和硒含氧阴离子的完全还原去除，大部分硝酸盐还原先于硒酸盐还原。氯霉素不抑制这些还原反应。能进行Se(VI)呼吸的嗜盐碱杆菌砷硒芽孢杆菌给出了类似的结果，但其Se(VI)还原酶在硝酸盐培养的细胞中不是组成型的。还原亚硒酸盐的亚硒酸盐还原芽孢杆菌未观察到Se(VI)的还原。对巴恩斯硫螺旋菌细胞膜制剂进行动力学实验的结果表明，存在组成型的硒酸盐和硝酸盐还原，以及在硝酸盐培养的细胞中存在一种可诱导的高亲和力硝酸盐还原酶，该酶对硒酸盐也有低亲和力。在毫摩尔浓度的硝酸盐存在下微摩尔浓度的Se(VI)同时还原表明，这些微生物可能在生物修复富含硝酸盐、含硒的农业废水中具有实际用途。用(75)Se-硒酸盐示踪剂得到的结果表明，这些微生物可以将环境中的Se(VI)浓度降低到符合新提出的将硒含氧阴离子释放到环境中的法规水平。
