Bioavailibility of Toxicants as Reflected in the In Situ Microbial Community Ecology and Relationship to Defensible End-Points

9814813白色污染有机化合物或金属对土壤和水的污染已被证明会改变环境中微生物的天然群落的组成。微生物群落从污染物影响中的恢复以及对环境的可能修复取决于许多因素，包括生物因素和非生物因素，这些因素在不同的时间范围和空间尺度上发挥作用。恢复和补救过程的一个关键决定因素是受影响的初始微生物群落的组成，包括分类代表性、个体种群的丰度和代谢状态。评估、表征和跟踪构成当地群落的所有微生物物种的能力已经通过分析两大类细菌化合物的现代分子方法大大增强：细菌细胞壁脂质和各种核糖体基因（通常是16S rRNA基因）的DNA序列。由于不需要在实验室中培养细菌，这些分子方法可以快速、准确地鉴定土壤或水样中的微生物种群，并初步指示其相对丰度和代谢状态。作为开发“标志性脂质生物标志物”方法的先驱，白色博士和他的同事们现在正在将该技术扩展到包括DNA序列分析，并将这些方法应用于对比密歇根州Wurtsmith空军基地和路易斯安那州Cocodrie沼泽两个主要现场位置的污染和未污染场地的研究，这两个地点都受到持续的碳氢化合物污染。一个总体目标是检验以下假设：随着污染物在空间（污染物浓度梯度）或时间（微生物生长和代谢的几个季节）中衰减，微生物群落组成将以定向和可预测的方式变化。正在检验的一个辅助假设是，是否有“哨兵”微生物物种表明特定的补救状态。针对污染土壤或沃茨的有效生物修复策略的发展已经从依赖于单一药剂（添加一种特定的细菌物种）的“银弹”方法转向更加生态的方法，该方法强调环境中微生物群落成员之间的代谢动力学。快速，准确地识别存在于当地社区的微生物的全方位越来越可能与使用现代分子方法的细胞壁脂质分析和诊断基因区域的DNA测序。反过来，微生物群落组成的表征可能会揭示与环境补救的各种状态相关的“哨兵”物种的独特组合。

9814813White Contamination of soil and water by polluting organic compounds or metals has been shown to alter the composition of native communities of microbes in the environment. Recovery by the microbial community from contaminant effects and possible remediation of the environment are dependent upon a host of factors, biotic and abiotic, operating over varying time frames and spatial scales. A critical determinant of the recovery and remediation process is the composition of the initial, affected microbial community, in terms of taxonomic representation, abundance of individual populations, and metabolic status. The ability to assess, characterize, and track all the microbial species comprising a local community has been greatly enhanced by modern molecular methods of analysis for two major classes of bacterial compounds: bacterial cell wall lipids, and the DNA sequence of various ribosomal genes (usually the 16S rRNA gene). Obviating the need to grow or culture the bacteria in the laboratory, these molecular methods can provide rapid, accurate identification of microbial populations within soil or water samples, and preliminary indications of their relative abundances and metabolic states. As a pioneer in the development of the "signature lipid biomarker" methodology, Dr. White and his colleagues are now expanding the technology to include DNA sequence analyses, and to apply these methods to the study of contrasting contaminated and uncontaminated sites at two major field locations, at Wurtsmith AFB in Michigan and at Cocodrie marsh in Louisiana, both subject to persistent hydrocarbon contaminations. One overall goal is to test the hypothesis that microbial community composition will change in a directional and predictable manner as contaminants are attenuated either in space (over a gradient of contaminant concentration) or through time (over several seasons of microbial growth and metabolism). An auxiliary hypothesis under test is whether there are "sentinel" species of microbes that signal particular states of remediation. The development of effective bioremediation strategies for contaminated soils or waters has been moving away from the "silver bullet" approach that relies upon a single agent (adding one particular bacterial species) to a more ecological approach that emphasizes metabolic dynamics among microbial community members in the environment. Rapid, accurate identification of the full range of microbes present in local communities increasingly is possible with the use of modern molecular methods of cell wall lipid analysis and DNA sequencing of diagnostic gene regions. In turn, the characterization of microbial community composition may reveal distinctive assemblages of "sentinel" species that correlate with various states of environmental remediation.