engleski

Genetic potential, diversity and activity of atrazine-degrading communities enriched from long-term atrazine contaminated soil

The aim of this work was to characterize atrazine-degrading bacterial communities enriched from an agrochemical factory soil. The communities designated as Z2, Z3 and Z4 mineralized 65-79% of [14C-ring]atrazine and 37-45% of [14C-ethyl]atrazine within 4 days of batch cultivation in mineral salts medium containing atrazine as the sole nitrogen source. Restriction analysis of amplified 16S rRNA (ARDRA) revealed high diversity and substantial differences in the bacterial composition of the enriched communities. The selected cloned sequences clustered within the Proteobacteria (α , 43% ; β , 28% and γ , 6%), the Actinobacteria (11%) and Bacteroidetes (6%). Three cloned sequences fell within TM7 phylum containing only environmental clones. Dominant ARDRA families in the Z2 library were highly similar to Ochrobactrum, Arthrobacter and Flavobacterium species, while the most abundant ARDRA families within the Z3 library were associated to the species of the genera Rhizobium, Ochrobactrum and Hydrogenophaga. The ARDRA families dominant in the Z4 clone library were related to Arthrobacter sp. and also to environmental clones recovered from oil and tetrachloride polluted soils. Atrazine-degrading genetic potential of the communities determined by PCR, revealed the presence of trzN-atzBC-trzD, trzN-atzABC-trzD and trzN-atzABCDEF-trzD gene combinations. The trzN-atzBC genes and IS1071 were located on 165-kb plasmid in all three communities. Redundancy in atzBC genes was observed as well. Quantitative PCR showed that the abundances of atzBCDEF genes relative to 16S rRNA ranged from 0.2 to 3.8% while the abundances of trzD ranged from 0.03 to 0.08%. The relative abundance of atzA gene in the community Z4 was approx. 200-fold lower than that of trzD gene. The communities presented in this work represent diverse bacterial associations exhibiting substantial atrazine mineralizing activity and complexity of atrazine-degrading genetic potential. Our study is beginning to yield insight into the diversity and genetic potential of atrazine-mineralizing communities that could be potential bioaugmentation agents for improving biotransformation processes in atrazine contaminated environments.

atrazine; biodegradation; atz; trz; bacterial community; contaminated soil; quantitative PCR

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