Genetic Heterogeneity Of Acidithiobacillus Strains Isolated From Different Geographic Location Based On RubisCO And 16S RRNA Gene Sequences

Object:The purpose was that whether populations of Acidithiobacillus spp. from different sources show significant regional and allopatric speciation. The ecological driving mechanism of genomic variation was clarified during evolution. Mechanism of genome variation of(?)extreme environment and its role in the ecological adaptability were revealed. Those provide a theoretical basis for understanding microbial phylogeography, diversity maintaining mechanism and molecular microbial geography.Methods:Taxonomic identity and genetic variability of Acidithiobacillus spp. isolated was determined by partial 16S rRNA gene sequences, functional genes clone library and repetitive-element PCR fingerprint. The ecological driving mechanism of genomic variation was analyzed by parameters of functional gene genetic diversity.Conclusions:Results of our research in Acidithiobacillus spp. from different regions as follows:1. One hundred and sixty strains were isolated from three different sites in China. Twenty strains were separated from the first solution with medium, five from the second medium and 135 from the third medium. Of the whole isolates grouped five cluster, six were identified as Acidithiobacillus ferrivorans, while 13 as representing A. ferridurans, YNTR4-15 and HBDY3-31 as Leptspirillum ferrooxidans and Lepto spirillum ferrodiazotrophum respectively, and the remaining strains were identified as A. ferrooxidans. It suggested that Acidithiobacillus spp. showed a great genetic diversity.2. cbbL and cbbM clone libraries of representative 30 indicated that cbbL gene of 21 were two copies (cbbL1 and cbbL2) and 9 possessed only cbbLl without cbbL2. In nucleotide-based trees, cbbL1 gene sequences of those strains were separated into three sequence types, and the cbbL2 was similar to cbbL1 with three types. Partail cbbM gene was single copy, with the exception of the XJFY2S-18.3. The base composition of cbbL gene was 58.5-63.5% G+C and 48.7-57.8% G+C3s (in the third position of codons). While the G+C content of cbbL2 gene was 59.4-64.8% and G+C3s was 61.0-65.9%. As for cbbM gene, the G+C content was 61.0-65.2% and G+C3s was 61.0-65.9%. Those indicated that codon bias was not obvious of RubisCO genes in Acidithiobacillus spp. Ka/Ks for nucleotide sequences of cbbLl and cbbL2 gene of Acidithiobacillus spp. was 0.5578 and 0.4238, respectively, which indicated the cbbL had evolved in all lineages under negative or purifying selection. However, the ratio (ω=Ka/Ks) for the nucleotide sequences of cbbM gene was 1.9880, which suggested the gene had positive selection. The value of the similarity was 88-100% and 89-100% at the level of nucleotide sequence of cbbLl and cbbL2 genes respectively. But the value of sequence similarity between cbbLl and cbbL2 of Acidithiobacillus spp. was 73-78%, which was low. In addition, the value of sequence similarity was 82-100% at the level of nucleotide sequence of cbbM gene. Those as well as repetitive-element PCR fingerprint indicated a great genetic diversity in Acidithiobacillus spp.