Differential expression of sulfur assimilation pathway genes in Acidithiobacillus ferrooxidans under Cd2+ stress: evidence from transcriptional, enzymatic, and metabolic profiles
Differential expression of sulfur assimilation pathway genes in Acidithiobacillus ferrooxidans under Cd2+ stress: evidence from transcriptional, enzymatic, and metabolic profiles
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DOI：
10.1007/s00792-014-0728-8
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发表时间：
2015-01
期刊：
影响因子：
2.9
通讯作者：
Chunli Zheng;Minjie Chen;Zhanlong Tao;Li Zhang;Xue Feng Zhang;Jian-Ying Wang;Jianshe Liu
中科院分区：
文献类型：
--
作者：
Chunli Zheng;Minjie Chen;Zhanlong Tao;Li Zhang;Xue Feng Zhang;Jian-Ying Wang;Jianshe Liu
Acidithiobacillus ferrooxidansis a heavy metal-tolerant acidophilic chemolithotroph found in acidic mine effluent and is used commercially in the bioleaching of sulfide ores. In this work, we investigated the interplay between divalent cadmium (Cd2+) resistance and expression of genes involved in the sulfur assimilation pathway (SAP). We also investigated the response of the thiol-containing metal-chelating metabolites, cysteine and glutathione(GSH), to increasing Cd2+concentrations. During growth in the presence of 30 mM Cd2+, the concentrations of mRNA for 5 genes in the SAP pathway increased more than fourfold: these encode ATP sulfurylase (ATPS), adenosine 5′-phosphosulfate (APS) reductase, sulfite reductase (SiR), serine acetyltransferase (SAT) and O-acetylserine (thiol) lyase (OAS-TL). Increased transcription was also reflected in increased enzyme activities: those of SAT and adenosylphosphosulfate reductase (APR) reached a peak of 26- and 15.8-fold, respectively, compared to the control culture in the presence of 15 mM Cd2+. In contrast, the activity of OAS-TL, which is responsible for the biosynthesis of cysteine, was diminished. At the metabolite level, the intracellular cysteine and GSH contents nearly doubled. These results suggested that Cd2+induced transcription of SAP genes, while directly inhibiting the activities of some enzymes (e.g., OAS-TL). Overall, these results are consistent with a detoxification/resistance mechanism involving enhanced sulfur uptake and sequestration of Cd2+by cysteine and glutathione.
