CHARACTERISATION OF THE BACTERIAL COMMUNITY STRUCTURE IN TOXIC CHEMICAL CONTAMINATED SOIL BASED ON ANALYSIS OF SINGLE STRAND CONFORMATION POLYMORPHISM OF 16S rRNA GENE

Abstract

Several toxic chemicals were sprayed by the US Army during Vietnam War and until now some fonner military bases in Middle and South Vietnam have been polluted by there toxicants that contaminated with varying levels of dioxin. These toxic chemicals have hazardous affect to humans and biological diversity, including microorganisms, Biostimulation of indigenous microorganisms to degrade contaminants seems to be a cost effective and environmentally safe method of bioremediation, In soil, aerobic bacteria playa very important role in biodegradation process to contaminants. However, bacterial population which can be cultured by standard laboratory conditions is only 0,01 to 10% of bacterial community in the nature. In this study, nine soil samples containing various concentrations of toxic .chemicals and dioxin were collected from different sites of former military base in Danang, and culture independence bacterial diversity was analyzed based on single strand conformation polymorphism (SSCP) of 16S rRNA gene. Dry soil samples HDN4 and HDN6 located near the highly contaminated sites showed less diversity than those collected at the other sites. There is no significant difference in bacterial diversity between lower contaminated sample HDN9 where grass can grow and eight higher contaminated samples HDNI to HDN8. 46 DNA clones excised from SSCP gel were sequenced and compared. Microbial community structure in these soils is identified to belonged to the classes of Actinobacleria, ACidobacleria, a, fJ and r-Proteobacteria. 2,4-0 and 2,4,5-T degrading bacteria in the genus Burkholderia and the family Burkholderiaceae seem to be dominant in all of the nine contaminated soil samples. Several soil bacteria such as Frateuria, Nevsia, Bradyrhi=obium, A=ospirillum and other acidiphilic bacteria Acidocella, ACidiphillum and Acidobacterium were also detected.