Genomic plasticity of Acidithiobacillus caldus SM-1 at different temperatures

Abstract:

[Objective] The aim of this study is to gain the acclimated strain of Acidithiobacillus caldus SM-1 with high activity when growing at the temperatures below the optimum, and elaborate its genomic plasticity and adaptation at different temperatures.[Methods] Strains were incubated at 37℃, 40℃ and 45℃. We used 454 genome resequencing technology to find the single nucleotide mutant sites in genome. The genes including mutant sites were studied to understand their relationship with the temperature adaptation.[Results] By long-term breeding, we obtained strains with higher viability than unacclimated strain at temperatures (37℃), which is lower than initial optimum growth temperature (45℃). Resequencing results showed the genome of SM-1 with high plasticity. In the genome of different strains (incubated at 37℃, 40℃ and 45℃), 418, 384 and 347 single nucleotide mutation sites were accumulated, respectively. Among them, 20 mutant sites were commonly occurred in the three strains. The genes they affected are involved in heavy metals and toxic resistance system, DNA methylation and protein acylation, and nucleic acid metabolism. In comparison, the specific mutations of the strains, grown at the 37℃ and 40℃, were related to energy metabolism, signal transduction and DNA/RNA stability. Three genes contained mutant sites are common in L37 and M40, of which, Atc_1031 and Atc_1623 encode proteins related to transposon insertion, Atc_1130 encodes a hypothetical protein that is similar to the out membrane protein assembly factor B or the disulfide bond formation protein with 23% and 35% similarity. In addition, some single nucleotide mutations cause the amino acid changes of the related proteins during the adaption.[Conclusion] The genome of At. caldus SM-1 showed highly plasticity at different temperatures. The study provided a set of genomic data for understanding the temperature adaptability molecular mechanism of microorganisms. The study revealed that At. caldus SM-1 evolved to fit lower temperature through multiple pathways, not only by the general environment adaptation mechanism of microorganism, but also by the specific pathway of the strain.