| Acid mine drainage(AMD)is one of the main pollutants from human mining activities.It is characterized by a low p H value usually below 3.5 and contains an elevated concentration of metal ions,which causes serious harm.In the formation of AMD ecosystems,acidophilic bacteria play an important catalytic role.Therefore,in order to understand the formation mechanism and evolution process of the AMD,control the production and mitigate the environmental impacts of the pollution,we need to comprehensively understand the physiological properties and adaptation mechanism of key acidophiles in AMD ecosystems.In this study,three isolates of acidophilic bacteria were isolated and purified from AMD samples collected from a pyrite mine in Anhui Province.Their physiological and biochemical properties were systematically studied,and the molecular mechanism of their adaptation to extreme environments was analyzed at the genome level.The main research results are as follows:1.Three isolates of acidophilic bacteria were isolated and purified from AMD with p H of 3.01.After 16 S r RNA gene sequencing and phylogenetic analysis,they were identified as Ralstonia sp.BW,Ralstonia sp.BP and Acidocella sp.SW,respectively.2.All the bacteria were heterotrophic acidophiles.The growth pH range of Ralstonia sp.BW is 3.0-7.0,with an optimum p H of 3.0-4.5,and the optimum temperature is 30 ?.It can grow in a 0-5% Na Cl environment.The growth p H range of Ralstonia sp.BP p H is 2.0-6.5,the optimum p H is 3.0-5.0,the optimum temperature is 30 ?,and it can grow in 0-5% Na Cl environment.Acidocella sp.SW grew in a p H range of 2.5-6.0,the optimum p H is 3.0-3.5,and the optimum temperature is 35 ?.It grew in 0-3% Na Cl environment.3.The isolates of bacteria can all tolerate high concentrations of heavy metals,but their performance is different.Ralstonia sp.BW had the strongest tolerance to Zn,with the tolerance concentration as high as 10 000 mg/L.The tolerance concentrations to Cu,Cd and Ni were 1 000 mg/L,1 000 mg/L and 150 mg/L,respectively.Ralstonia sp.BP had the strongest tolerance to Cd(up to 2000 mg/L)but was sensitive to Cu,Zn,and Ni,with tolerance concentrations of 50 mg/L,200 mg/L and 15 mg/L,respectively.Acidocella sp.SW has the strongest tolerance to Zn,up to 15000 mg/L.It also has a strong tolerance to Cd,Cu and Ni,which are 2000 mg/L,1000 mg/L and 500 mg/L,respectively.4.Genomic studies showed that these three bacteria had similar adaptive mechanisms.They are rich in desaturase genes(Des A,OLE1,ERG3),which can maintain the impermeability of H+ by regulating the composition of cell membranes.The gene encoding H+-ATPase(Ntp I)is also abundant in the genome,which can pump H+ out of cells actively,thus maintaining the neutral environment of cells.5.Bacteria are rich in heavy metal resistance genes,such as cobalt-zinc-cadmium efflux system(Czc D)and cationic transport ATPase(Znt A).Through the action of these enzymes,divalent metals such as zinc,nickel,cadmium,cobalt,copper and Hg can be actively released out of cells.The arsenic transporter(Acr3)on the cell membrane enables the bacteria to resist arsenic whereas,cation/multidrug efflux transporter(Acr B)can also help bacteria eliminate or inhibit the accumulation of heavy metals and other toxic substances. |
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