title: Differential gene expression in response to copper in Acidithiobacillus ferrooxidans strains possessing dissimilar copper resistance.
abstract: Locus afe_0454 from Acidithiobacillus ferrooxidans (At.ferrooxidans) is annotated as related to copper resistance in The Institute for Genomic Research database. In our study, two At.ferrooxidans strains, 26(#) and DC, with different levels of copper ion resistance were isolated from acid mine drainages at two major copper mines in China, and their copper-resistance capacity was determined. The 26(#) strain had a copper-tolerance level of 0.22 mol/L, whereas the DC strain had a lower copper-tolerance level of 0.04 mol/L. The mutant 26(#) was generated from strain 26(#), and its copper-tolerance level was 0.25 mol/L. Using real-time quantitative reverse transcription polymerase chain reaction, differential expression of the afe_0454 gene during copper ion stress of these three strains was investigated. The results showed that the expression of afe_0454 was increased under copper ion stress, indicating that the afe_0454 gene is sensitive to copper levels. Furthermore, the afe_0454 gene expression ratio varied in the different copper-resistant strains. Gene expression was highest in the highest copper-resistant strain. The deduced amino acid sequence of the afe_0454 gene was 56.87% non-polar, indicating the AFE_0454 protein was hydrophobic. Searching with the AFE_0454 protein in The Institute for Genomic Research database showed that the structure of the copper resistance protein D (CopD), which transports copper ions outside of the cell, had the highest sequence identity (46%). Bioinformatics analysis showed that the AFE_0454 protein has eight transmembrane helixes and was predicted to be localized to the plasma membrane. These results strongly suggested that the AFE_0454 protein is likely a transmembrane protein and might be directly involved in copper ion resistance.
authors.affiliation: School of Minerals Processing & Bioengineering, Central South University, Changsha, China. xueling0714@yahoo.com.cn
authors.forename: Xueling
authors.initials: X
authors.lastname: Wu
authors.forename: Qi
authors.initials: Q
authors.lastname: Hu
authors.forename: Dongmei
authors.initials: D
authors.lastname: Hou
authors.forename: Bo
authors.initials: B
authors.lastname: Miao
authors.forename: Xueduan
authors.initials: X
authors.lastname: Liu
mesh_terms: D042763:Acidithiobacillus / Q000187:drug effects / Q000235:genetics*; D000595:Amino Acid Sequence; D002681:China; D003300:Copper / Q000378:metabolism* / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D008565:Membrane Proteins; D003300:Copper