Architecture of thermal adaptation in Exiguobacterium sibiricum strain 255-15: A genome and transcriptome approach. Exiguobacterium artemiae 255-15

Several microorganisms have wide temperature growth range and versatility to tolerate large thermal fluctuations in diverse environments. To better understand thermal adaptation of psychrotrophs, Exiguobacterium sibiricum strain 255-15 was used, a psychrotrophic bacterium that grows from -5°C to 39°C. Its genome is approximately 3 Mb in size, has a GC content of 47.7% and includes 2,978 putative protein-encoding genes (CDS). The genome and transcriptome analysis along with the organism's known physiology was used to better understand its thermal adaptation. A total of about 27%, 3.2% and 5.2% of E. sibiricum strain 255-15 CDS spotted on the DNA microarray yielded differentially expressed genes in cells grown at -2.5°C, 10°C and 39°C, respectively, when compared to cells grown at 28°C. The hypothetical and unknown genes represented 10.6%, 0.89% and 2.3% of the CDS differentially expressed when grown at -2.5°C, 10°C and 39°C versus 28°C. The transcriptome analyses showed that E. sibiricum is constitutively adapted to cold temperatures since little differential gene expression was observed at growth temperatures of 10°C and 28°C, but at the extremities of its Arrhenius growth profile, namely -2.5°C and 39°C, much more differential gene expression occurred. The genes that responded were more typically associated with stress response. Keywords: stress response to cold and hot temperatures Overall design: Six-condition experiment: -2.5°C vs10°C, -2.5°C vs 28°C, -2.5°C vs 39°C, 28°C vs10°C, 28°C vs 39°C, 10°C vs 39°C. Biological replicates: 6 replicates grown and harvested independently for each different temperature (-2.5°C, 10°C, 28°C and 39°C). One replicate per array.

多种微生物在多样生境中拥有宽泛的生长温度范围，且具备耐受剧烈温度波动的适应性。为深入解析嗜冷菌（psychrotrophs）的温度适应机制，本研究选用西伯利亚微小杆菌（Exiguobacterium sibiricum）255-15菌株——这是一种可在-5℃至39℃区间生长的嗜冷细菌。该菌株基因组大小约为3 Mb，GC含量为47.7%，共包含2978个推定蛋白质编码基因（CDS）。
本研究结合基因组与转录组分析，以及该菌株已知的生理特性，进一步解析其温度适应策略。
与在28℃下培养的细胞相比，在-2.5℃、10℃和39℃下培养的西伯利亚微小杆菌255-15菌株中，分别有约27%、3.2%和5.2%的CDS在DNA微阵列（DNA microarray）中被鉴定为差异表达基因。
在-2.5℃、10℃和39℃相较于28℃的培养条件下，差异表达基因中假定功能基因与未知功能基因分别占比10.6%、0.89%和2.3%。
转录组分析结果表明，西伯利亚微小杆菌对低温环境存在组成型适应：在10℃与28℃的生长温度下仅检测到极少量的差异基因表达；但在其阿伦尼乌斯生长曲线的极端温度区间，即-2.5℃和39℃，则出现了大量的差异基因表达。响应温度胁迫的基因大多与应激反应相关。
关键词：冷热温度应激反应
整体实验设计：共设置6组对比实验，分别为-2.5℃ vs 10℃、-2.5℃ vs 28℃、-2.5℃ vs 39℃、28℃ vs 10℃、28℃ vs 39℃、10℃ vs 39℃。生物学重复：针对-2.5℃、10℃、28℃及39℃四种培养温度，每种温度均独立培养并收获6个生物学重复；每个DNA微阵列对应1个生物学重复。