Multiple strains of sulfate-reducing bacteria（SRB）were isolated from sulfate wastewater treatment bioreactor and determined by polymerase chain reaction（PCR） with SRB-specific 16S ribosomal RNA gene primers.One of the strains isolated,strain F28-1 was further studied by sequencing the complete 16S ribosomal RNA gene,testing carbon resource utilization,and demonstrating the key enzyme gene structure related to sulfate metabolism,dissimilatory sulfite reductase（Dsr）gene.Blast retrieving results indicated that the SRB belonged to Desulfovibrio,its 16S ribosomal RNA gene sequence was similar to Desulfovibrio desulfuricans subsp.desulfuricans strain Essex 6（AF192153）,with identity 99.9%,and therefore,the strain was named as D.strain F28-1.Strain F28-1 was able to use glucose,propionic acid,lactic acid,acetic acid,ethanol and methanol as sole carbon resource and reduce sulfate to sulfide.It removed 95% sulfate within 72 h in a lab-scale experiment with lactic acid as electron donor.ORF finder program checked out two open reading frames（ORFs）in dsr gene sequence,dsrA and dsrB,which had 14% identity.Corresponding α-and β-subunit amino acid sequences were obtained according to the DNA sequence.α-subunit contained two conserved motifs,i.e.（C-X5-C）-Xn-（C-X3-C）,which was required for binding to siroheme; and CP-Xn-C-X2-C-X2-C required for binding to Fe4S4 clusters.In addition,the β-subunit contained only the Fe4S4 clusters binding site,but the siroheme binding site was missing.The SRB,which had multi-substrates utilization and high sulfate reduction power,supplies the starting bacterium for enhancing the efficiency of sulfate wastewater treatment.The detailed knowledge of the enzyme structure provides the target for the quantitative PCR gene locus and helps to improve its biological sulfate-removal potential.
