Genetic Diversity And Phylogeny Of Silicate Bacteria Isolated From Saline-alkali Soils In The North Part Of China

Genetic diversity and phylogeny of 43 silicate bacterium strains isolated from saline-alkali soils collected from Tianjing, Shandong, Hebei and Heilongjiang Provinces in the northern China, together with two reference strains, were determined by analysis ofRAPD, BOXAIR-PCR, 16S rDNA RFLP and 16S rDNA full qequence of two representative strains was analyzed to construct the 16S rDNA phylogeny.Six single RAPD primers and 2 TP-RAPD primers were choosen for analysis of genetic diversity. The strains were divided into 13 genetic groups at the level of 82.5% similarity by RAPD with six single primers. The result of TP-RAPD was a little different from RAPD, but had higher resolution degree, which made more significant genetic difference among the tested strains; and all strains were divided intol3 groups at the level of 85.5% similarity. Combination of RAPD and TP-RAPD analysis, these strains were divided into 13 genetic groups at the level of 82% similarity: groupâ… , groupâ…¡and groupâ…¢and groupâ…©â…¢were mainly constituted by the silicate bacteria from Heilongjiang Province; other tested strains overlap in distribution in groupâ…£, groupâ…¤, groupâ…¥, groupâ…§, groupâ…¨and groupâ…«, which showed there was no correlation between genetic groups and the geographic origin; TJ28, VKPM B-7519 and HB24 formed independent groups respectively. The combined analyzing result was similar to that of RAPD with single primers, which indicated that the analysis of RAPD had better dependability when the experimental condition was steady and consistent.The results of BOXAIR divided the strains into 12 groups at the level of 75% similarity, which demonstrated that there were great genetic differentiations among the tested silicate bacteria, and there was no correlation between genetic groups and the geographic origin.The results of 16S rDNA PCR-RFLP analysis also showed that there was very diverse in phylogeny among the tested strains. Based on the 16S rDNA restriction patterns by Mspâ… , Haeâ…¢, Hhaâ… and Hinfâ… , nine 16S rDNA genotypes were generated. Dendrogram constructed by 16S rDNA PCR-RFLP analysis divided the strains into eight genetic groups, and groupâ… was the biggest one containing 30 strains, including the type strain of Bacillus mucilaginosus VKPM B-7519, which showed that most silicate bacteria isolated from saline-alkali soils should belong to B. mucilaginosus in taxonomy. Meanwhile, a new biger genetic group containing 6 cilicate sWains was formed, and it was different from the reference strains.The phylogenic tree of the representative sWains HLJ01 (GenBank accession EF031269) and HB 16 (GenBank accession EF031270) was constructed by analysis of the 16S rDNA full sequence, the results of analysis of 16S rDNA sequence revealed that swain HLJ01, HB 16 and Bacillus mucilaginosus and Bacillus edaphicus were located in the same phylogenic branch. HLJ01 and HB16 had high homology with Bacillus mucilaginosus in the phylogenic tree, but the 16S rDNA sequence of HLJ01 only has the identity of 96.7% with Bacillus mucilaginosus, and of HB16 has the identity of 95.5% with Bacillus mucilaginosus. With Bacillus edaphicus, the 16S rDNA sequence of HLJ01 has the identity of 94.6%, and of HB16 has the identity of 93.3 %. The homology analysis showed that strains HLJ01 and HB16 probably represented new species in the genus of Bacillus; hence, further studies, such as the G+C mol% content, DNA hybridization, should be done to determine their exact taxonomic position.