REU: A Molecular Approach to Understanding the Genetic Response of Soil Microbial Populations Under Selection

密歇根州立大学的威廉·E·霍尔本博士和詹姆斯·M·蒂杰博士建议采用分子方法来理解基因生态学，并在施加选择压力的情况下进行交换--环境中的外来化学物质。过去的微生物生态学研究几乎没有提供关于土壤中微生物种群遗传变化的信息。这一疏漏尤其明显，并不是说基因工程微生物的释放问题引发了一些问题，而目前几乎没有数据来支持对风险的解释。为了研究这种变化，需要一种可以在DNA水平上遵循的有效和生态敏感的选择。研究人员选择了一种新能源--除草剂的生物降解作为研究系统。他们提出了一种假设，即在首次引入时，本地和土壤微生物种群在使用新能源方面并不是遗传优化的，但在反复暴露后，将选择增强种群使用这些化学物质能力的基因变化。通过使用基因特异性探针、DNA限制性内切酶分析、杂交和相关的分子方法，他们可以区分五种最可能的遗传反应：(I)导致基因表达改变的调控变化；(Ii)导致新的代谢活动的突变；(Iii)遗传信息的重排或放大；(4)将遗传信息转让给类似生物；(5)将遗传信息转让给异化生物。虽然这些类型的基因变化在实验室中发生几乎是毫无疑问的，但关于哪些是自然界中普遍发生的变化，以什么频率和在什么条件下发生，几乎没有信息。为了提供这些信息，他们建议使用化学药物、土壤微观世界、实地研究和对经过20年农化处理的种群进行回顾分析来研究这些变化。这种方法的连续体应该使他们能够推断实验室和现场之间关于机制和频率的信息。关于后者的信息完全缺乏。这是科学界几个团体(例如，监管机构)以及一个努力通过基因操作制造“安全的”新生物体及其产品的行业进行的极其及时和亟需的研究。调查人员和他们的组织因其在该领域的专业知识而闻名于世。

Drs. William E. Holben and James M. Tiedje of Michigan State University propose taking a molecular approach to understanding gene ecology and exchange under an applied selection pressure -xenobiotic chemicals in the environment. Past research in microbial ecology has provided virtually no information on genetic changes of microbial populations in soil. This omission is particularly apparent, not that the issue of release of genetically engineered microorganisms has raised questions for which little data exists to underpin interpretations of risk. To study such change, an effective and ecologically sensible selection that can be followed at the DNA level is needed. The investigators have chosen the biodegradtion of a new energy resource -- herbicides -- as the system of study. They proposed to test the hypothesis that the native and soil microbial population is not genetically optimized for use of a new energy resource when first introduced, but that after repeated exposure, genetic changes will be selected that enhance the ability of populations to use these chemicals. By using gene-specific probes, DNA restriction analysis, hybridization and related molecular methods, they can distinguish among the five most likely genetic responses: (i) regulatory changes resulting in altered gene expression; (ii) a mutation which results in a new metabolic activity; (iii) rearrangement or amplification of genetic information; (iv) transfer of genetic information to similar organisms; (v) transfer of genetic information to dissimilatory organisms. While there is little doubt that these types of genetic changes that occur in the laboratory, there is little information on which are to prevalent changes that occur in nature, at what frequency and under what conditions. To provide this information, they propose to study these changes using chemostats, soil microcosms, field studies and a retrospective analysis of populations after 20 years of agrochemical treatment. This continuum of approaches should allow them to extrapolate information on mechanism and frequency between laboratory and field. Information on the latter is entirely lacking. This is extremely timely and much needed research by several groups in the scientific community (e.g., regulatory agencies) as well as by an industry struggling to make "safe" new organisms and their products by genetic manipulation. The investigators and their organization are world renowened for their expertise in this field.