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Title: ISOLATION AND 16S DNA CHARACTERIZATION OF TROPICAL SOIL MICROORGANISMS CAPABLE OF UTILIZING THE HERBICIDES HEXAZINONE AND TEBUTHIURON

Author
item MOSTAFA, FADWA - SELF EMPLOYED
item HELLING, CHARLES

Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2003
Publication Date: 11/3/2003
Citation: Mostafa, F.I., Helling, C.S. 2003. Isolation and 16S DNA characterization of tropical soil microorganisms capable of utilizing the herbicides hexazinone and tebuthiuron. Journal of Environmental Science and Health. B37(6):783-797.

Interpretive Summary: Two herbicides showing excellent potential for controlling illicit coca plants were known to disappear from the tropical soil to which they were applied, but the mechanism of loss has never been proven. In this study, six soil bacteria were isolated from soils of Hawaii (USA) and Colombia (South America), identified as to species by DNA fingerprinting, and shown to utilize either hexazinone or tebuthiuron herbicide as their sole carbon and nitrogen source. As the first known identification of any microorganism that degrades hexazinone or tebuthiuron (herbicides used worldwide for nearly 40 years in agriculture and forestry), the research significantly increases our knowledge of their environmental fate, especially in tropical ecosystems.

Technical Abstract: Six non-fermentative bacteria were isolated from Colombian (South America) and Hawaiian (USA) soils after enrichment with minimal medium supplemented with two herbicides, hexazinone (Hex) and tebuthiuron (Teb). Microscopic examination and physiological tests were followed by partial 16S DNA sequence analysis, using the first 527 base pairs of the 16S rRNA gene for bacterial identification. The isolated microorganisms (and in brackets, the herbicide that they degraded) were identified as: from Colombia, Methylobacterium organophilum [Teb], Paenibacillus pabuli [Teb], and Microbacterium foliorum [Hex]; and from Hawaii, Methylobacterium radiotolerans [Teb], Paenibacillus illinoisensis [Hex], and Rhodococcus equi [Hex]. The findings further explain how these herbicides, which have potential for illicit coca (Erythroxylum sp.) control, dissipate following their application to tropical soils.