BIODEGRADATION OF PARAQUAT BY THE NOVEL BACTERIAL STRAIN AEROMONAS VERONII NK67 FROM CASSAVA FIELDS IN THAILANDNUTTABODEE VIRIYAWATTANA AND S. SURACHAT
The herbicide paraquat residues in Cassava field have been shown to cause adverse human health effects and soil degradation, leading to decreased crop productivity. Bioremediation is the effective way to solve this problem. This study focused on selecting soil bacteria that are capable to degrade paraquat. The 283 soil samples were collected from Cassava field in Nakhon Ratcha Sima provinces, because of paraquat is one of the most widely used chemical herbicides in this area. All 112 isolates have been isolated. Among them, there were 6 isolates tolerance to paraquat concentration 1 mM, including 4 and 2 strains of Clostridium spp. and Aeromonas spp., respectively. The isolates were further tested for their efficacy to degrade paraquat. The results showed that only two strains of Aeromonas spp. (strain NK 66 and NK 67) were able to degrade paraquat. It was found that levels of paraquat decreased to 4.9 ppm (24.36%) and 10.68 ppm (53.4%) after exposed to Aeromonas spp. Strain NK 66 and NK 67, respectively. Molecular Methods to Identify Aeromonas spp. strain NK 67 using PCR-amplified 16S rRNA genes sequencing were employed. Nucleotide sequence of 16S rRNA from Aeromonas spp. strain NK 67 was compared with nucleotide sequences from GenBank database by using BLAST program. The results showed that 99% similar to 16S rRNA from A. veronii strain ATCC 35624, according to the results of classification by Bergeys Manual of Systematic Bacteriology. Then it can be conclude that this bacteria is A. veronii NK67 (JN880412). This is the first report that A. veronii exhibited high efficiency to degrade paraquat which can be further applied for remediation of paraquat in contaminated areas and going for commercial production.
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