Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada.
Can J Microbiol. 2012 Apr;58(4):402-12. doi: 10.1139/w2012-010. Epub 2012 Mar 21.
Freeze-thaw stress has previously been shown to alter soil community structure and function. We sought to further investigate this stress on enriched microbial consortia with the aim of identifying microbes with ice-associating adaptations that facilitate survival. Enrichments were established to obtain culturable psychrotolerant microbes from soil samples from the latitudinal extremes of the Canadian Shield plateau. The resulting consortia were subjected to consecutive freeze-thaw cycles, and survivors were putatively identified by their 16S rRNA gene sequences. Even though the northerly site was exposed to longer, colder winters and large spring-time temperature fluctuations, the selective regime similarly affected both enriched consortia. Quantitative PCR and metagenomic sequencing were used to determine the frequency of a subset of the resistant microbes in the original enrichments. The metagenomes showed 22 initial genera, only 6 survived and these were not dominant prior to selection. When survivors were assayed for ice recrystallization inhibition and ice nucleation activities, over 60% had at least one of these properties. These phenotypes were not more prevalent in the northern enrichment, indicating that regarding these adaptations, the enrichment strategy yielded seemingly functionally similar consortia from each site.
先前的研究表明，冻融胁迫会改变土壤群落结构和功能。本研究旨在进一步探究这种胁迫对富集微生物群落的影响，以鉴定出具有冰结合适应性从而促进生存的微生物。本研究从加拿大盾地高原的南北极土壤样本中获得可培养的耐冷微生物，建立了富集培养以获取耐冷微生物。所得的混合培养物经过连续的冻融循环，根据 16S rRNA 基因序列推测存活的微生物。尽管北方站点经历了更长、更冷的冬季和春季较大的温度波动，但选择压力同样影响了两个富集培养物。采用定量 PCR 和宏基因组测序来确定原始富集物中抗性微生物的亚群的频率。宏基因组分析显示了 22 个初始属，只有 6 个属在选择前存活下来且并不占优势。对存活微生物进行冰晶再结晶抑制和冰核活性分析，超过 60%的微生物具有至少一种这些特性。在北方的富集物中并没有更普遍的存在这些特性，这表明在这些适应性方面，富集策略从每个地点都产生了看似功能相似的混合培养物。
