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

Abstract:

[Objective] Investigate the effect of pH, 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. [Methods] 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 of A. 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, Acry_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. cryptum 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).

Key words:Acidiphilium cryptum, Hexavalent chromium reduction, Orthogonal experimental design, Real time-qPCR