Masters Theses

Keywords and Phrases

165 rRNA sequencing; Denaturing gradient gel electrophoresis (DDGE); Mesorhizobium sp


"The discovery of several members of the Leguminosae family growing on a TCE contaminated site demonstrated that they have the capabilities to tolerate the TCE contamination. This led to an investigation of the plants' ability to metabolize TCE. Research by Dr. Lee Newman showed that nodules from Crotalaria spectabilis grown on the site had TCE metabolites present while nodules from other legumes at the site did not. The presence of TCE metabolites within the C. spectabilis nodules suggests that the bacterial symbiont may be responsible for TCE metabolism. This led us to investigate the symbiont of C. spectabilis and its ability to metabolize TCE. Nodules from C. spectabilis grown on TCE contaminated and non-contaminated soils were used to isolate the bacterial symbiont. Some species of Crotalaria are known to host Methylobacterium nodulans and this unique symbiont may explain why only the C. spectabilis nodules metabolize TCE. However, methane and methanol enrichments from the nodules were not successful and led to other approaches of isolating and identifying the symbiont. Sequencing of the 16S rRNA gene amplified from crushed nodules identified the symbionts as members of the Mesorhizobium genus. Symbiotic bacteria were isolated from control and dosed nodules and isolates of potential symbionts were verified by comparing PCR products from nodules and isolates using DGGE analysis. Sequencing of the 16S rRNA gene from the isolate confirmed that the isolates are members of the genus Mesorhizobium. This bacterium is different from symbionts isolated from other Crotalaria species and represent a new bacterium capable of nodulating Crotalaria sp. Attempts to demonstrate TCE metabolism by the isolated symbionts were unsuccessful suggesting that TCE metabolism may depend on a partnership with the host plant"--Abstract, page iii.


Westenberg, David J.

Committee Member(s)

Mormile, Melanie R.
Burken, Joel G. (Joel Gerard)


Biological Sciences

Degree Name

M.S. in Applied and Environmental Biology


Missouri University of Science and Technology

Publication Date

Fall 2011


ix, 46 pages

Note about bibliography

Includes bibliographical references (pages 64-66).


© 2011 April Lyn Rocha, All rights reserved.

Document Type

Thesis - Open Access

File Type




Subject Headings

Crotalaria spectabilis
Gel electrophoresis
Nucleotide sequence
Trichloroethylene -- Biodegradation

Thesis Number

T 9941

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