PABs (polyphosphate accumulating bacteria) are a type of bacteria that can absorb large amounts of phosphate and store it as intracellular polyphosphate, which helps with biological phosphorus removal in waste-water treatment. In the Mekong Delta, Vietnam, a genetic diversity of PAB community was isolated from samples of water and sludge from intensive catfish ponds, as well as effluent water and sludge from piggery waste-water treated by bio-digesters. There are 48 isolates out of a total of 439 that have the potential to accumulate intracellular poly-phosphate, as evidenced by the following main characters: rod-shaped or short rod-shaped; motile, twitching movements or non-motile; expression of poly-phosphate electron dense granules within the cells; accumulated poly-phosphate from poly-phosphate kinase gene 1; intracellular poly-phosphate content According to a phylogenetic tree for partial 16S rRNA genes, 22 strains isolated from intensive catfish ponds are classified into four classes: Bacilli, Actinobacteria, Beta-proteobacteria, and Gamma-proteobacteria; and 26 strains isolated from piggery waste-water treated by bio-digesters are classified into four classes: Bacilli, Actinobacteria, Alpha-proteobacteria, The process of analysing and comparing the genetic diversity of 48 isolates revealed that 16S rRNA sequences have high variability nucleotide regions interspersed with low variability nucleotide regions. In the PAB population, the variation of and Pi index formed different types of haplotypes; there were 25 haplotypes (genotypes) from 48 sequences. The structural differences between haplotypes resulted in a high level of diversity (Hd=0.91). In the evolutionary process of bacterial strains capable of high poly-P accumulation, the levels of haplotype diversity created many genotypes for genetic variation and the ability to adapt to the environment. The nucleotide and haplotype diversity of the strains isolated in piggery waste-water treated biodigesters (Pi=0.16, h=14) were lower and the genetic conservation was higher than isolated strains in intensive catfish ponds (Pi=0.18, h=16), according to a comparison of genetic diversity between populations of bacteria isolated from two sampling places. This is the scientific foundation for choosing sample sources for isolating and selecting polyphosphate-accumulating strains.
Author (S) DetailsLe Quang Khoi
Department of Science and Technology of Tien Giang province, Vietnam
Truong Trong Ngon
Biotechnological Research and Development Institute, Cantho University, Vietnam
Cao Ngoc Diep
Biotechnological Research and Development Institute, Cantho University, Vietnam
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