Kourtev Peter S, Nakatsu Cindy H, Konopka Allan
Department of Biological Sciences, 915 W. State Street, Purdue University, West Lafayette, IN 47907-2054.
Appl Environ Microbiol. 2006 Jan;72(1):628-37. doi: 10.1128/AEM.72.1.628-637.2006.
Chromium (VI) is toxic to microorganisms and can inhibit the biodegradation of organic pollutants in contaminated soils. We used microcosms amended with either glucose or protein (to drive bacterial community change) and Fe(III) (to stimulate iron-reducing bacteria) to study the effect of various concentrations of Cr(VI) on anaerobic bacterial communities. Microcosms were destructively sampled based on microbial activity (measured as evolution of CO2) and analyzed for the following: (i) dominant bacterial community by PCR-denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene; (ii) culturable Cr-resistant bacteria; and (iii) enrichment of iron-reducing bacteria of the Geobacteraceae family by real-time PCR. The addition of organic C stimulated the activities of anaerobic communities. Cr(VI) amendment resulted in lower rates of CO2 production in glucose microcosms and a slow mineralization phase in protein-amended microcosms. Glucose and protein amendments selected for different bacterial communities. This selection was modified by the addition of Cr(VI), since some DGGE bands were intensified and new bands appeared in Cr(VI)-amended microcosms. A second dose of Cr(VI), added after the onset of activity, had a strong inhibitory effect when higher levels of Cr were added, indicating that the developing Cr-resistant communities had a relatively low tolerance threshold. Most of the isolated Cr-resistant bacteria were closely related to previously studied Cr-resistant anaerobes, such as Pantoea, Pseudomonas, and Enterobacter species. Geobacteraceae were not enriched during the incubation. The studied Cr(VI)-contaminated soil contained a viable anaerobic bacterial community; however, Cr(VI) altered its composition, which could affect the soil biodegradation potential.
六价铬对微生物有毒，会抑制污染土壤中有机污染物的生物降解。我们使用添加了葡萄糖或蛋白质（以驱动细菌群落变化）以及铁（III）（以刺激铁还原菌）的微观生态系统，来研究不同浓度的六价铬对厌氧细菌群落的影响。根据微生物活性（以二氧化碳的释放量来衡量）对微观生态系统进行破坏性采样，并分析以下内容：（i）通过16S rRNA基因的PCR-变性梯度凝胶电泳（DGGE）分析优势细菌群落；（ii）可培养的耐铬细菌；（iii）通过实时PCR分析地杆菌科铁还原菌的富集情况。添加有机碳刺激了厌氧群落的活性。添加六价铬导致葡萄糖微观生态系统中二氧化碳的产生速率降低，而在添加蛋白质的微观生态系统中矿化阶段缓慢。葡萄糖和蛋白质的添加选择了不同的细菌群落。这种选择因添加六价铬而改变，因为在添加六价铬的微观生态系统中，一些DGGE条带增强，并且出现了新的条带。在活性开始后添加的第二剂六价铬，当添加较高水平的铬时具有强烈的抑制作用，这表明正在形成的耐铬群落具有相对较低的耐受阈值。大多数分离出的耐铬细菌与先前研究的耐铬厌氧菌密切相关，如泛菌属、假单胞菌属和肠杆菌属。在培养过程中地杆菌科没有富集。所研究的受六价铬污染的土壤中含有一个有活力的厌氧细菌群落；然而，六价铬改变了其组成，这可能会影响土壤的生物降解潜力。
