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

污染有机化合物或金属造成的土壤和水的白色污染已被证明会改变环境中本地微生物群落的组成。微生物群落从污染影响中恢复和可能的环境补救取决于许多因素，包括生物和非生物因素，这些因素在不同的时间框架和空间尺度上发挥作用。恢复和修复过程的一个关键决定因素是最初受影响的微生物群落的组成，包括分类代表、单个种群的丰度和代谢状态。对两大类细菌化合物：细菌细胞壁脂类和各种核糖体基因(通常是16S rRNA基因)的DNA序列的现代分子分析方法大大提高了评估、表征和跟踪组成一个局部群落的所有微生物物种的能力。这些分子方法不需要在实验室中培养或培养细菌，可以快速、准确地识别土壤或水样中的微生物种群，并初步表明它们的相对丰度和代谢状态。作为开发“标志性脂质生物标记物”方法的先驱，White博士和他的同事们现在正在扩展这项技术，以包括DNA序列分析，并将这些方法应用于对比密歇根州的Wurtsmith AFB和路易斯安那州的Cocodrie Marsh这两个主要野外地点的污染和未受污染的地点，这两个地点都受到持久性碳氢化合物污染的影响。一个总体目标是检验这样一个假设，即随着污染物在空间(在污染物浓度的梯度上)或随着时间(在微生物生长和新陈代谢的几个季节中)减弱，微生物群落组成将以定向和可预测的方式变化。一个正在测试的辅助假设是，是否存在发出特定补救状态信号的“哨兵”微生物物种。对受污染的土壤或水体制定有效的生物修复策略，已经不再是依赖单一制剂(添加一个特定细菌物种)的“银弹”方法，而是强调环境中微生物群落成员之间的代谢动力学的更生态的方法。随着细胞壁脂类分析和诊断基因区域DNA测序的现代分子方法的使用，快速、准确地鉴定存在于当地社区的各种微生物越来越成为可能。反过来，微生物群落组成的特征可能揭示与环境修复的不同状态相关的独特的“哨兵”物种组合。

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.