TitleMolecular and phenotypic characterization of Zn-resistant methylobacterium spp. in soil systems
NameKist, Jennifer (author), Tate, III, Robert L. (chair), Young, Lily Y. (internal member), Yee, Nathan (internal member), Wawrik, Boris (outside member), Rutgers University, Graduate School - New Brunswick,
Growth (Plants)--Molecular aspects,
Growth (Plants)--New Jersey
DescriptionMethylobacterium species, pink-pigmented facultatively methylotrophic bacteria (PPFMs), have the potential facilitate agricultural and bioremediation processes through plant growth promotion, zinc cycling and biofilm production. Phenotypic and genetic studies of Methylobacterium strains were conducted to increase our understanding of the roles and evolution of PPFMs and to develop methods for characterizing environmental isolates to help realize their potential. Chapter 1 describes the isolation of Methylobacterium isolates from a New Jersey agricultural soil. mxaF, the structural gene for the methanol dehydrogenase enzyme, was compared with the 16S rRNA gene during the characterization of 114 PPFM isolates from agricultural soil, forest soil and blueberry skin. PPFM isolate 16S rRNA sequences were too similar to distinguish them at the species level. 16S rRNA sequences clustered tightly phylogenetically whereas mxaF clustering paralleled phenotypic patterns. Soil type, pH and plant cover did not influence Methylobacterium geographic distribution or select for specific mxaF sequences, indicating a reason for the widespread nature and versatility of PPFMs in the environment. A phylogenetic survey of archived GenBank® sequences is presented in Chapter 2. mxaF, mxaF-like and mxaF’ sequences were included with xoxF and other pyrroloquinoline-quinone-(PQQ)-dependent methanol/ethanol dehydrogenase sequences. Methylobacterium mxaF sequences clustered tightly, even with other bacterial genera similar methylotrophy genes present. mxa gene family operon construction revealed evidence of horizontal gene transfer (HGT). HGT events could not be confirmed by examining G+C content of mxa genes. It is unclear whether the PPFM mxa operon construction pattern is the ancestor or the descendant of those of other genera. Biofilm production, a major mode of colonization for plant-associated bacteria, is addressed for Methylobacterium species in Chapter 3. The effects of various substrates and Zn concentrations on biofilm development were investigated. Low levels of Zn did not inhibit biofilm production but did affect time-dependently affect the amount of DNA per gram of biofilm material in a time-dependent manner. Chapter 4 addresses Zn tolerance in PPFMs. Isolates exbitied precipitation of a white solid, clearing zone production, or growth with neither phenomenon. Isolates solubilized hopeite, a Zn phosphate compound. This ability can potentially raise the bioavailability of Zn in soils and was not described for this genus prior to this research. Plant growth-promotion of red clover (Trifolium pratense) seeds and seedlings by PPFM isolates is described in Chapter 5. Not all Methylobacterium species promoted plant growth, indicating the importance of determining individual ability of PPFM isolates.
NoteIncludes bibliographical references
Noteby Jennifer Kist
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.