Digital imaging and modeling of the growth of Trichoderma virens strains designed to degrade methyl parathion /
Digital imaging of Trichoderma virens strains GvT6 and Tv29-8 at four different temperatures (16, 22, 27, and 32⁰C) determined that strain GvT6, which contains a bacterial gene (opd) that encodes an enzyme (OPH) that degrades organophosphates achieves less overall growth after an 8 day period than t...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=728415741&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Digital imaging of Trichoderma virens strains GvT6 and Tv29-8 at four different temperatures (16, 22, 27, and 32⁰C) determined that strain GvT6, which contains a bacterial gene (opd) that encodes an enzyme (OPH) that degrades organophosphates achieves less overall growth after an 8 day period than that of strain Tv29-8, the parental strain. The growth response to temperature follows the same overall pattern achieving maximal growth at 27⁰C. However, strain GvT6 is less responsive to temperature variations than strain Tv29-8. A model was constructed from the growth data that predicted fungal growth for both strains using radial growth data fit to the Ratkowsky equation to determine growth rate and fit to the Arrhenious equation to determine decline rate. The model accurately predicted growth in the observed temperature and time ranges. Finally, variations in OPH, resulting from site-specific mutations in opd, with altered activity against methyl parathion were assayed in crude and purified form to determine which modifications enhanced degradation of methyl parathion . Two forms of the modified enzyme, 254R and 257L, were chosen for transformation into T. virens. Isolates transformed with these plasmids, as well as a strain transformed with plasmid PCL6 (Xu et al., 1996), were tested for enzyme activity in shake cultures, the most enzyme activity was observed at 22⁰C. Measurement of the growth rate of these transformants on plates saturated with differing concentrations of methyl parathion at 27⁰C determined that two strains of T. virens TvPCL6 and Tv254R had less sensitivity to methyl parathion than strain GvT6. Measurement of growth in soil microcosms demonstrated that this in vitro difference in growth was also a significant difference in the soil environment. |
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| Item Description: | Vita. "Major Subject: Plant Pathology". |
| Physical Description: | xiii, 149 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 124-139). |