Project description:The study identified a total of 3169 gene transcripts (98.4% coverage). By comparing the anaerobic versus aerobic H2-oxidizing At. ferrooxidans cultures, a total of 371 DEGs were found. Of these, 168 DEGs were increased significantly during the aerobic growth on H2 (with O2 as the sole electron acceptor), while 203 DEGs increased significantly during anaerobic growth on H2 (with Fe3+ as the sole electron acceptor).
Project description:The outer-membrane c-type cytochrome Cyc2 is generally considered to be the initial electron acceptor in iron respiratory chain of Acidithiobacillus ferrooxidans ATCC 23270, a model microorganism in acidophilic bioleaching environment. In our work, however, the knockout of cyc2 did not result in impaired Fe(II) consumption or growth capacity. To screen the potential genes for alternative initial electron acceptors other than Cyc2, RNA-Seq was employed to compare global gene expressions in the A. ferrooxidans ATCC 23270 wild type and the Δcyc2 mutant grown on Fe(II) or switched energy source from S0 to Fe(II). The data focused on 29 up-regulated and 19 down-regulated genes in the mutant under both conditions, among which AFE_1428 was the most highest one. in-silico analysis also suggested that the product of AFE_1428 might act as an alternative initial electron acceptor when Cyc2 was absent, which needs to be further validated.
Project description:A 1.3-kb insertion sequence, termed ISAfe1 (U66426), from Acidithiobacillus ferrooxidans ATCC 19859 is described. ISAfe1 exhibits the features of a typical bacterial insertion sequence. It has 26-bp, imperfectly matched, terminal inverted repeats and an open reading frame (ORF) that potentially encodes a transposase (TPase) of 404 amino acids (AAB07489) with significant similarity to members of the ISL3 family of insertion sequences. A potential ribosome-binding site and potential -10 and -35 promoter sites for the TPase ORF were identified, and a +1 transcriptional start site was detected experimentally. A potential outwardly directed -35 site was identified in the right inverted repeat of ISAfe1. A second ORF (ORF B), of unknown function, was found on the complementary strand with significant similarity to ORF 2 of ISAe1 from Ralstonia eutropha. Southern blot analyses demonstrated that ISAfe1-like elements can be found in multiple copies in a variety of A. ferrooxidans strains and that they exhibit transposition. A codon adaptation index (CAI) analysis of the TPase of ISAfe1 indicates that is has a CAI of 0.726 and can be considered well adapted to its host, suggesting that ISAfe1 might be an ancient resident of A. ferrooxidans. Analysis of six of its target sites of insertion in the genome of A. ferrooxidans ATCC 19859 indicates a preference for 8-bp pseudopalindromic sequences, one of which resembles the termini of its inverted repeats. Evidence is presented here that is consistent with the possibility that ISAfe1 can promote both plasmid cointegrate formation and resolution in E. coli.
Project description:Cadmium is one of several heavy metals present in contaminated soils. Apparently, it has no biological role but can produce DNA damage, overexpression of stress response proteins and misfolded proteins, amongst other deleterial effects. Acidithiobacillus ferrooxidans is an acidophilic bacterium capable of resisting very high concentrations of heavy metals such as cadmium. This is important for industrial bioleaching processes where Cd+2 concentrations can be in the range of 5-100 mM. Cadmium resistance mechanisms in these microorganisms have not been fully characterized. A. ferrooxidans ATCC 53993 contains genes coding for possible metal resistance determinants such as efflux systems belonging to three families: P-type ATPases, RND transporters and cation diffusion facilitators (CDF). In addition, it has some extra copies of these genes in its exclusive genomic island (GI). Several of these putative genes were characterized in the present report by determining their transcriptional expression profiles and functionality. Moreover, a global quantitative proteomic analysis was carried out to further explore new cadmium resistance determinants in this biomining acidophile. Changes in iron oxidation pathways, upregulation of transport proteins (P-type ATPases and CDFs) and changes in ribosomal protein levels were seen. Finally, increased concentrations of exclusive putative cadmium ATPases present in strain ATCC 53993 GI and other non-identified proteins such as Lferr_0210, which forms part of a possible operon, could explain its greater resistance to cadmium compared to other acidophiles such as A. ferrooxidans ATCC 23270.