隐藏嗜酸菌Acidiphilium cryptum XTS的Cr(Ⅵ)还原特性及相关基因的差异表达

Reduction characteristics and differential expression of Acidiphilium cryptum XTS Cr(Ⅵ)-reduced related gene

【目的】考察p H值、初始Cr(VI)浓度、Fe(III)的加入及氧气含量对隐藏嗜酸菌Acidiphilium cryptum XTS还原Cr(VI)的影响及其六价铬还原相关基因在不同培养条件下的差异表达。【方法】采用正交试验法L9(34)优选Cr(VI)还原最适条件;根据模式菌A.cryptum JF-5同源功能基因序列设计引物,对菌株XTS中的六价铬还原相关基因Acry_2099在不同培养条件下的基因差异表达进行分析。【结果】p H为2.9,初始Cr(VI)浓度为80 mg/L,Fe(III)浓度为100 mg/L的条件是该菌株还原Cr(VI)的最优化配合比,在该条件下处理24 h,Cr(VI)的还原率达到67.48%;从菌株XTS中成功克隆了Acry_2099基因,其序列与模式菌A.cryptum JF-5的同源功能基因序列一致性达到了99.7%;在不同p H值、初始Cr(VI)浓度及氧气含量下Acry_2099基因表达上调情况与Cr(VI)还原速率呈一致趋势,证明Acry_2099很可能参与还原Cr(VI)的代谢途径。虽然加入Fe(III)能促进Cr(VI)的还原,但是铁的加入对Acry_2099基因表达水平没有显著的影响。【结论】A.cryptum XTS对Cr(VI)的还原与p H值、初始Cr(VI)浓度、Fe(III)的存在等因素有关,较低的p H和较高的初始Cr(VI)浓度对该菌还原Cr(VI)具有促进作用。

[Objective] Investigate the effect ofpH, initial Cr（VI） concentration, the existence of Fe（Ⅲ） and oxygen concentration on Cr（Ⅵ） reduction conducted by A. cryptum XTS, and monitor differential expression of the functional gene involved in Cr（Ⅵ） reduction process. [Methodsl The orthogonal experiment L9（34） has been utilized to find the optimal condition for Cr（Ⅵ） reduction; The sequence of gene Acry_2099, which is thought to be involved in Cr（Ⅵ） reduction pathway ofA. cryptum XTS has been cloned and analyzed. [Results] It has been shown that the optimal condition of Cr（Ⅵ） reduction by A. cryptum XTS is at pH 2.9 under the help of 100 mg/L ferric ion with initial 80 mg/L Cr（Ⅵ）. In this condition, 67.48% Cr（Ⅵ） has been reduced in 24 hours. In addition, Aery 2099 has been cloned and its sequence shares 99.7% similarity with its homolog in A. cryptum JF-5, the model A. cryptum species. The alternation of Acry_2099 expression level correlates with the ability of Cr（Ⅵ） reduction in different condition including different pH, initial Cr（Ⅵ） concentration as well as oxygen concentration, which suggests Acry_2099 may be involved in Cr（Ⅵ） reduction pathway. Even though the addition of ferric iron can enhance the Cr（Ⅵ） reduction by A. eryptum XTS, ferric iron addition have no obvious influence on Acry 2099 gene expression. [Conclusion] The environmental factors including pH, initial Cr（Ⅵ） concentration, the existence of Fe（Ⅲ） and oxygen concentration greatly affect the ability of reducing Cr（Ⅵ） by A. cryptum XTS. To be specific, low pH and high initial Cr（Ⅵ） concentration promotes A. cryptum XTS ability to reduce Cr（Ⅵ）.