极端嗜酸硫杆菌Acidithiobacillus spp.种群的遗传多态性及分子地理学研究

目前国内外对陆生环境微生物种群内微多样性及谱系地理分化的研究报道较少。由于栖息环境的隔离和极端的生存条件，极端微生物成为研究材料的首选。我们前期研究发现，地理分布较广的极端嗜酸细菌Acidithiobacillus ferrooxidans存在显著的种群遗传多态性，但不清楚地理隔离和生态位差异对其系统发育和种群分化的影响。本项目根据种群遗传学、生态学原理，采用持家基因多序列分析、分子指纹分型、宏基因组文库构建及生理生态参数的测定，通过生态型模拟(ES)和AdaptML软件分析亚种群生态生理参数与遗传多态性参数的相关性，在不同空间尺度范围，阐明异质环境的生态位和地理隔离对亲缘关系非常相近亚种群的产生和分化的作用及成种模式；同时采用q-PCR、RT-PCR分析不同选择环境对核心基因和适应性基因在转录水平上的差异，揭示环境选择对种群分化的影响。为了解微生物谱系地理和多样性维持机制提供理论依据。

Microorganisms are the most abundant and potentially most diverse organisms in the biosphere. However, to date, knowledge of the origin, maintenance and distribution of diversity on terrestrial microorganisms remains limited. Biogeography constitutes a cornerstone approach for studying biodiversity patterns at different taxonomic levels in the prokaryotic world. In this regard, the importance of geographic barriers influencing microbial speciation is subjected to great debate. .A DNA sequence-based approach can help overcome these challenges, because the bacteria falling into sequence clusters can correspond to ecologically distinct populations. The ecotype model is highly attractive as it describes evolutionary and ecological principles that might account for microbial population structures and speciation. To date, research on bacterial population genetics has been restricted almost entirely to pathogenic and relevant symbiotic bacteria，knowledge about the relevance of pedigree geography and ecological strategies in natural populations of free-living bacteria is extremely limited..We recently showed that the extremely acidophilic bacterium Acidithiobacillus ferrooxidans can be isolated from different parts of the world in sites as diverse as mining area, hot sulfur spring. Moreover, since their natural habitats are ecologically extremely diverse, different Acidithiobacillus ferrooxidans strains exhibit a high degree of interstrain genetic variability. The extreme conditions and geographical isolation of its environments are optimal circumstances for observing allopatric speciation..In this work, we are going to evaluate the importance of different evolutionary forces in shaping the genetic structure of Acidithiobacillus ferrooxidans populations distributed in six acidic mining areas, by using phylogenetic and population genetics approaches based on multilocus sequence analyses coupled to genomic fingerprintings (PFGE, rep-PCR, AFLP)..To conclude, our specific objectives are: (ⅰ)to identifying the smallest sequence clusters corresponding to ecologically meaningful putative ecotypes, and test whether putative ecotypes exhibit specie-like properties.(ⅱ) to clarify whether putative ecotypes of Acidithiobacillus populations coexist in a particular environment, indicating the occurrence of sympatric differentiation among closely related iron-oxidizing Acidithiobacillus populations.(ⅲ)to examine to which degree geographic distance has an influence on genitic structure in Acidithiobacillus spp. and test whether barriers to dispersal or ecological selection are primarily responsible for its differentiation.(ⅳ)To test whether there has been genetic divergence and local adaptation of Acidithiobacillus populations to prevailing environmental conditions.