Transcriptomic Analysis Reveals Sulfur Oxidation Mechanism In Acidithiobacillus Ferriphilus

The sulfide minerals exposed to water and oxygen when they heaped on the ore mountains,which was easy to produce acid mine drainage(AMD)containing a large quantity of heavy metal ions via chemical and biological oxidation reaction.However,the involvement of the Acidiphilics would accelerate the oxidative rates of sulfide minerals.The thesis identified the Acidithiobacillus ferrooxidans Z1 by sequencing it's 16S rRNA and constructing the 16S rRNA phylogenetic tree.The result indicated that the studied strain was more closely in phylogeny to the strain Acidithiobacillus ferriphilus M20,then named it A.ferriphilus SCUT-1 primarily.The Acidithiobacillus ferriphilus is chemoautotrophic bacterium,oxidizing ferrous ion and inorganic sulfides to obtain energy.Investigation of the sulfur oxidation mechanism in A.ferriphilus can help to have an overview knowledge of the formation mechanism of AMD involving of microoganism,and make basis for studying the producing and treating of AMD.The study inoculatd the strain A.ferriphilus SCUT-1 in 9K-FeSO4,obtain the bacteria at the log phase,and extract the bacteria's genome,being sequenced in pair-ends on the Illumina HiSeqTM 2500 platform.The genome sequencing results confirmed the validity of identifying the present strain as A.ferriphilus;and the genes involved in sulfur and ferrous iron oxidation are identified based on the genome analysis.Subsequently,the present strain was inoculated in 9K-FeSO4,9K-S?,9K-FeS2 medium respectively,then monitored the growth states and the changes in the concentration of the substrates.Extraction 3 RNA samples from each of the three media for the RNA-Seq experiment,and named F-1,F-2,F-3,S-1,S-2,S-3,FS-1,FS-2,FS-3 respectively.About 2.5 Gb data was obtained from the high-throuthput sequencing by Illumina HiSeqTM 2500 for each RNA samples.Three compares(FeS2lFe2+,S0/Fe2+ and FeS2lS0)were set for screening significant different expressed genes(SDEGs)by the means of Edge R and the CPM values,the screening criteria were p<0.05,IFold changel ? 1.5 and FDR<0.05.The genes involved in sulfur oxidation in the present study strain are supposed to be identified via the analysis of the SDEGs screened from these three compares.Based on the results,the soxY.soxZ and soxB genes involved in encoding sulfur oxidizing(Sox)complex,the hdr gene cluster(hdr A-B-C and tusA)encoding Heterodisulfide reductase and TusA,the soeA,soeC genes participated in encoding SoeABC complex involved in sulfite oxidation,and the cyoA-B-C-D gene cluster encoding the electron transfer components are significant up-regulated under the S-containing conditions,in other words,these genes are induced by inorganic sulfur compounds.Subsequently,conducted GO and KEGG pathway enrichment analysis for the SDEGs,the results shows that sulfur metabolism and oxidative phosphorylation are significant enriched under sulfur oxidation conditions,and they are suggest to be involved in sulfur oxidation.Based on the sulfur oxidation model of the widely studied acidithiobacilli strain released by now,together with the genes and pathways related to sulfur oxidation derived from the present study,a sulfur oxidation model of A.ferriphilus SCUT-1 is primarily constructed,which is most like the sulfur oxidation model of A.ferrooxidans ATCC23270 proposed by Quatrin et al among these models of acidithiobacilli strains released by now.The present study performed the first genome sequencing experiment for A.ferriphilus,and obtain the sulfur oxidation components in A.ferriphilus SCUT-1,primarily construct the sulfur oxidation pathways of A.ferriphilus SCUT-1,as well as provide a fruitful base for the research of the sulfur oxidation mechanism in acidithiobacilli.