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BACTERIAL COMMUNITIES CAPABLE OF ENHANCED EPTC AND ATRAZINE DEGRADATION IN OHIO SILT LOAM AND SILTY CLAY LOAM SOILS

Bardhan, Sougata
http://rave.ohiolink.edu/etdc/view?acc_num=osu1276270673

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Soil Science.
Approximately 7.5 – 8.0 million kg of EPTC (S-ethyldipropylthiocarbamate) and 32 million kg of atrazine (2-chloro-4-(ethylamine)-6-(isopropylamine)-s-triazine) are used each year for crop production in the United States. Recent reports have raised concern about continued use of these herbicides because of their negative impacts on aquatic life and potential endangerment of animal/human health. Therefore rapid degradation of these herbicides after intended action is important to prevent non-target pollution associated with their presence in the environment. In this study, a culture independent metagenome approach was used to identify bacteria capable of degrading EPTC and atrazine. Two different soils (Wooster silt loam and Luray silty clay loam) were evaluated for development of enhanced degradation by successive application of these herbicides. A polymerase chain reaction (PCR) technique was used to monitor the appearance of the specific genes thcA, thcB, thcC, thcD and thcR for EPTC degradation and atzB, atzD, trzD and trzN for atrazine degradation. Whereas no EPTC or atrazine degrading genes were detected in control soils, presence of these genes in the enhanced soils confirmed the higher degradation potential observed. A PCR-DGGE (Polymerase Chain reaction – Denaturing Gradient Gel Electrophoresis) method was used to amplify and characterize the V-3 (338 to 518) region of the 16s rRNA gene from soil DNA extracted from the enhanced soils to identify the dominant bacteria involved in the degradation of the herbicides. Unique DGGE band profiles obtained for each soil sample were used to calculate the bacterial richness index and Dice similarity index. The values for these indices showed that microbial community abundance and distribution was greatly impacted due to successive exposure of these two herbicides. Selected DGGE bands were excised, cloned and sequenced to identify the dominant bacterial species in the EPTC and atrazine enhanced soils. From the 16S rRNA clone libraries, a total of 64 clones were sequenced. DNA sequence data confirmed the presence of known EPTC and atrazine degrading bacterial species such as Sphingomonas sp., Rhodococcus sp., and Actinobacterium sp. Several uncultured bacterial species, earlier detected in aromatic chemicals contaminated sites, were also identified. Two bacterial species, Kaistobacter sp. and Gemmatomons sp., were identified that have not been reported yet as degraders of these two chemicals. Identification of novel bacterial species capable of degrading these herbicides provides evidence for the vast diversity in microbial communities that still remains to be explored. Knowledge gained about these bacterial degraders will be useful in elucidating novel pesticide degradation pathways and in developing methods for bioremediation to reclaim contaminated soils.
Warren Dick (Advisor)
Parwinder Grewal (Committee Member)
Edward McCoy (Committee Member)
John Cardina (Committee Member)
162 p.
Agronomy; Environmental Science; Microbiology; Soil Sciences
EPTC; atrazine; enhanced degradation; PCR; DGGE; bacterial community; bioremediation

Recommended Citations

Citations

  • Bardhan, S. (2010). BACTERIAL COMMUNITIES CAPABLE OF ENHANCED EPTC AND ATRAZINE DEGRADATION IN OHIO SILT LOAM AND SILTY CLAY LOAM SOILS [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276270673

    APA Style (7th edition)

  • Bardhan, Sougata. BACTERIAL COMMUNITIES CAPABLE OF ENHANCED EPTC AND ATRAZINE DEGRADATION IN OHIO SILT LOAM AND SILTY CLAY LOAM SOILS. 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1276270673.

    MLA Style (8th edition)

  • Bardhan, Sougata. "BACTERIAL COMMUNITIES CAPABLE OF ENHANCED EPTC AND ATRAZINE DEGRADATION IN OHIO SILT LOAM AND SILTY CLAY LOAM SOILS." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276270673

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.