Lee Changsoo, Kim Jaai, Do Hyojin, Hwang Seokhwan
School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Nam-gu, Pohang, Kyungbuk 790-784, Republic of Korea.
Water Res. 2008 Feb;42(4-5):1254-62. doi: 10.1016/j.watres.2007.09.017. Epub 2007 Sep 25.
Changes in microbial community structure, associated with changes in process performance, were investigated with respect to the sludge retention time (SRT) in bioreactors treating thiocyanate. Among the seven reactors operated at 0.8-3.0 d SRTs, respectively, the reactor at 2.0 d SRT displayed the maximal thiocyanate removal rate of 240.2mg/L/d. However, the thiocyanate removal efficiency suddenly decreased from 96.1% to 43.1% when the SRT was reduced from 2.0 to 1.8d, corresponding to a 50.1% drop in the removal rate. Microbial communities in the reactors operated at short SRTs, near washout, were analyzed by denaturing gradient gel electrophoresis (DGGE) based on bacterial 16S rRNA genes. All band sequences recovered were assigned to two phyla, Proteobacteria and Bacteriodetes. A Thiobacillus-like microorganism was commonly detected in all the reactors and is suggested to be the main organism responsible for thiocyanate decomposition. Several DGGE band sequences were closely related to the environmental clones detected in environments rich in sulfur and/or nitrogen compounds. Statistical analysis of the DGGE profiles demonstrated that the structure of thiocyanate-degrading communities, as well as the process performance, changed with change in SRT. The microbial community profiles were not always more closely related to those at similar SRT than those at less similar SRT on the non-metric multidimensional scaling (NMDS) map. This was also supported by clustering analysis. These results were contrary to the general notion that the community structures in continuous systems will be controlled by the washout of microbial populations. Our experimental results suggest that the structure of a microbial thiocyanate-degrading community at a given SRT would not be determined only by the washout effect.
在处理硫氰酸盐的生物反应器中，研究了与工艺性能变化相关的微生物群落结构随污泥停留时间（SRT）的变化情况。在分别以0.8 - 3.0天SRT运行的七个反应器中，SRT为2.0天的反应器显示出最大硫氰酸盐去除率，为240.2mg/L/天。然而，当SRT从2.0天降至1.8天时，硫氰酸盐去除效率突然从96.1%降至43.1%，相应地去除率下降了50.1%。基于细菌16S rRNA基因，通过变性梯度凝胶电泳（DGGE）分析了在接近洗出的短SRT下运行的反应器中的微生物群落。回收的所有条带序列被归为两个门，变形菌门和拟杆菌门。在所有反应器中均普遍检测到一种类似硫杆菌的微生物，据推测它是负责硫氰酸盐分解的主要生物体。几个DGGE条带序列与在富含硫和/或氮化合物的环境中检测到的环境克隆密切相关。对DGGE图谱的统计分析表明，硫氰酸盐降解群落的结构以及工艺性能随SRT的变化而变化。在非度量多维尺度（NMDS）图上，微生物群落图谱与相似SRT下的图谱并不总是比与不太相似SRT下的图谱更密切相关。聚类分析也支持了这一点。这些结果与连续系统中群落结构将由微生物种群的洗出控制这一普遍观念相反。我们的实验结果表明，在给定SRT下，微生物硫氰酸盐降解群落的结构不会仅由洗出效应决定。
