Isolation and Phylogenetic Analysis of Polyphosphate Accumulating Organisms in Water and Sludge of Intensive Catfish Ponds in the Mekong Delta, Vietnam

Abstract

Polyphosphate accumulating organisms were isolated from water and sludge samples of intensive catfish ponds in the Mekong Delta, Vietnam. The Results of estimation of intracellular polyphosphate concentration conducted on each of monocultures indicated that the content of intracellular polyphosphate varied from 2 mg/l to 148.1 mg/l after 6 days of incubation in the medium. Of 191 isolates, twenty-one have uptake and store intracellular phosphate from 19.6 to 148.1 mg/l. They have shaped like a rods and short rods or cocci, a few of them were slightly curved or straight or curved rods. The majority of them are gram-positive (76.2%) and the remains are gram-negative. The partial 16S rRNA genes of these isolates were sequenced and compared with bacterial 16S rRNA genes in Genbank using BlastN Program. Phylogenetic tree was constructed on the basic 16S rRNA gene sequences demonstrating the population of high phosphate accumulating bacteria obtained from samples of catfish ponds were affiliated with four major bacterial lineages. Twenty-one bacteria isolates from samples of catfish ponds included in four classes: Bacilli, Actinobacteria, Beta-proteobacteria, Gamma-proteobacteria. The majority of the strains showed excess phosphate accumulation. Strains related to Bacillus sp. were dominant bacteria group constituted up to 52.4% of all identified isolates, but high phosphate accumulating bacteria are Burkholderia vietnamiensis TVT003L within class Beta-proteobacteria, Acinetobacter radioresistens TGT013L within Gamma-proteobacteria and Arthrobacter protophomiae VLT002L within class Actinobacteria. Methyl blue Loeffler’s staning and electron microscopy examination confirmed that the bacteria had stored polyphosphate granules intracellularly.