Thesis (Ph.D.) Dept of Microbiology, University of Adelaide, 1982. / Typescript (photocopy).

Thesis (Ph.D.) -- University of Adelaide, Department of Microbiology, 1979. / Journal reprint in end pocket.

Thesis (Ph. D.)--West Virginia University, 1998. / Title from document title page. "December 11, 1998." Document formatted into pages; contains ix, 94 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2008. / Härtill 4 uppsatser.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 74-80).

Thesis (M. Sc.)--University of Canterbury, 2004. / Typescript (photocopy). "June 2004." Includes bibliographical references (leaves 105-113). Also available via the World Wide Web.

Five new genes apparently involved in the metabolism of cell wall peptidoglycan by Escherichia coli are described. One of these, designated murH, was mapped at 99 min on the E. coli linkage map. The murH1 mutant exhibited temperature- sensitive (ts) growth which was associated with a block in a late step in peptidoglycan synthesis and with peptidoglycan hydrolase-mediated lysis at the restrictive temperature. The murH locus could not be cloned in multicopy vectors but was readily cloned in a single copy phasmid vector derived from phage λ. The instability of murH in multicopy prevented its further characterization. As an alternative approach to characterizing the murH function, extragenic mutations which suppressed the murH1 ts lysis phenotype were isolated. One suppressor mutation, designated smh-A1, (25 min on the genetic linkage map) restored temperature resistance in murH1 mutants but otherwise had no distinguishable phenotype. A second extragenic murH1 suppressor, smhB1 (13 min) conferred a ts lysis phenotype by itself. Interestingly, a combination of murH1 and smhB1 resulted in cosuppression of their lysis phenotypes. The suppressor activities of the smhA1 and smhB1 alleles were relatively specific in that they failed to suppress lysis caused by either mutational (murE or murF) or antibiotic-induced blocks in peptidoglycan synthesis. Two additional ts lysis mutations, lytD1 (mapped at 13 min) and lytE1 (25 min), arose spontaneously in smhB1 and smhA1 backgrounds, respectively. The smhA1 allele suppressed the lysis phenotype of lytE1 but not of lytD1. Furthermore, the combination of smhB1 with either lytD1 or lytE1 resulted in cosuppression of their lysis phenotype. The specificity of the suppressor activities, combined with the similarities in the phenotypes of the mutants representing this collection of loci, suggested functional relationships between the murH, smhA, smhB, lytD, and lytE loci. Four clones which complemented the lytD1 mutation were obtained by screening an E. coli gene library, but it is shown that the complementing activity did not represent the E. coli chromosomal lytD locus. It is shown instead that 2 phage λ genes, identified as cro and cI, accounted for the lytD1 complementing activities in these clones. Evidence is presented which suggests that these clones were derived from phage λ DNA which was fortuitously present as a contaminant in the vector preparation used for construction of the gene library. Since the λ Cro and CI proteins are DNA-binding proteins which bind to identical 17 base-pair recognition sequences (the λ right operator sequences), it is hypothesized that LytD encodes a DNA-binding protein with a similar specificity (i.e., which binds to a λ right operator-like sequence) which regulates, probably negatively, the expression of a gene(s) involved in some way with peptidoglycan hydrolysis. / Graduate

M.Sc. / An increasing problem in subtropical regions, such as South Africa, is the susceptibility of various banana varieties to Fusarium wilt by the soil borne pathogen Fusarium oxysporum tsp. cubense (FOC). In this study the problem of fungal susceptibility of banana was addressed by investigating the biochemical aspects of cell wall strengthening in banana roots. Defence responses were induced in both adult and tissue culture tolerant Goldfinger and susceptible Williams banana cultivars by treatment of the plants with a heat-released elicitor preparation from the mycelial cell walls of FOC race 4 and the crude filtrate. Banana plants were maintained in a hydroponic system, before being inoculated with the elicitor and crude filtrate preparation. Differences in lignin content, callose deposition, phenolics and the enzymes involved in cell wall strengthening; (PAL, CAD, POD and PPO) between the tolerant and susceptible banana cultivars were investigated. Differences in defence responses after treatment with elicitor and with crude filtrate were observed, but it was shown that the former is a more efficient experimental system for the characterisation of susceptible and tolerant responses in banana cultivars. An elicitor concentration of 45 4g/m1 greatly induced cellular POD, PPO, PAL and CAD activity in Goldfinger, whereas no significant increase was observed for Williams. Lignin content increased significantly in Goldfinger compared to Williams. The quantitative determination of induced total phenolics, phenolic glycosides, phenolic esters and cell wall-bound phenolic acids were higher in Goldfinger than in Williams. These increases in the four phenolic subfractions were clearly confirmed by reverse phase HPLC. No significant increase in callose accumulation was observed for both cultivars. The obtained results indicate an important role for cell wall strengthening as an inducible defence mechanism of banana roots against FOC race 4.

The plant cell wall is a vitally important interface connecting plant cells to their outside environment and neighboring cells. Acting as a hub for defense, signaling, and physiological processes, the plant cell wall was a crucial innovation in plant evolution. Current cell wall models are largely based on what has been observed in plants like Arabidopsis, Pisum sativum, Nicotiana tabacum, and Phaseolus vulgaris. These models are unable to consider the variety of polymers in a given wall, the mechanical and functional properties such polymers impart, and the complexity of interactions among polymeric cell wall constituents. This work deepened the understanding of wall composition of specialized walls that fall outside of the scope of current plant cell wall models. A detailed survey of cell wall polymer distribution in the transfer cell walls in three key bryophyte species the model moss Physcomitrium patens, hornwort Phaeoceros carolinianus, and liverwort Marchantia polymorpha was done utilizing histochemical techniques in the light and florescent microscopes coupled with immunocytochemical localization with monoclonal antibodies (MAbs) in the transmission electron microscope (TEM). This work demonstrated that the occurrence, abundance, and types of polymers differ among taxa and between the two generations, are more influenced by developmental and life history needs than the similar function of the cells in individual taxa. A notable difference between generations was seen in M. polymorpha with the LM2 and JIM13 MAbs targeting AGP epitopes. However, findings in P patens appear to lack the differential labeling observed in both M. polymorpha and P. carolinianus. Using these same techniques, the walls and matrices involved in the process of spermatogenesis were examined in the moss P. patens and noted differences in abundance and location of cell wall polymers during sperm cell differentiation. Another notable finding of this work was that high concentrations of arabinose as components of AGP and pectins are important in the walls of P. patens during the process of spermatogenesis. The final study focused on utilizing herbarium specimens to explore the application of immunogold localization on dried collections of the moss Polytrichum up to 100 years old. The studies compiled in this dissertation demonstrate that the major cell wall components, cellulose, pectins, hemicelluloses, and callose, are constituents of special walls in three bryophytes, but they are differentially expressed within cell types and across these plants. Taken together, these works contribute significant new data on the composition of plant cell walls by focusing on bryophytes and the unique cell walls vital to the life history processes of spermatogenesis and placental function. These findings also show that both field-collected and herbarium samples are successfully labeled with MAbs at the TEM level, unlocking the potential for further studies across time and taxa using plant collections.