Vibrio vulnificus is a marine pathogen of human health concern, capable of causing potentially fatal wound infections in a select group of the population. Previous studies have indicated this species’ strong negative correlation with salinity, not typically found above 30 ppt. This study assessed the ability of V. vulnificus to become Viable But Nonculturable in response to elevated salinity (35 ppt) as well as investigated novel methods for confirming their entrance into this state. Results showed a complete loss of culturability in both Environmental and Clinical strains of this bacterium by 9 days after inoculation. Using a High Content Imager, it was determined that these pathogens were not dying (< 10%) in response to the treatment and were partially becoming cocci (≈35%). This study indicates the importance of understanding the impact environmental parameters have on this human pathogen, and what it means for reliably detecting them. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Thesis submitted to the Division of Veterinary and Biomedical Sciences. Bibliography: leaves 237-283.

One of the major aims of the research presented in this thesis was to assist managers of native vegetation communities in southeastern Australia in understanding the dynamics of P. cinnamomi with an important ecological species, Xanthorrhoea australis. It trialed the use of phosphite in large-scale field applications to establish the usefulness of this management option for the first time on Victorian flora. This thesis describes the process of disease development within mature X. Australia plants. For the first time it was shown that within X. australis plants, secondary disease symptoms are related to the percentage of stem that has been infested by the disease. It was evident that after initial invasion the pathogen moves via root xylem and throughout the plant within vascular to the stem, especially within the desmium. The research shows that the pathogen could not be isolated consistently even though it was considered to be responsible for disease symptoms. Trials of a control fungicide (Foli-R-fos 200) shows that protection occurs in many susceptible plants when 2 and 6g a.i./L phosphite is applied. Phytotoxicity occurred in native plants at Anglesea and within controlled environment trials when using ≥ 6g a.i./L. It will be shown that 2g a.i./L phosphite controls disease in sprayed plots within heathlands at Anglesea and a recently burnt coastal woodland community at Wilson’s Promontory. The proportion of healthy X. australis plants treated with phosphite was significantly higher than the proportion in control plots without phosphite. The research shows that phosphite was recovered from leaves of three species treated with Foli-R-fos 200 in the field. For the first time it has been shown that seed germination was reduced in two species when high concentrations of phosphite were applied. The first documentation of the effect that phosphite has on soil properties showed that nitrogen and oxidised organic carbon were the only parameters to alter significantly. This thesis provides answers to some important questions, answers that can now be used by managers in formulating better policies and actions at an operational level. There has been a dire need in Victoria to address many issues regarding P. cinnamomi and this thesis provides relevant and informative approaches to disease control, and a better understanding of the disease progress.

The entrainment of microbes from agricultural land into overland flow during rainfall events is recognised as an important source of pathogenic microbes to surface water bodies and yet this transport process is poorly understood. In this study, a method has been developed to separate bacteria into the forms in which they have been postulated to exist in overland flow. Then Escherichia coli was used as a model organism to investigate the transported state of bacteria eroded from cowpats and their subsequent transport in overland flow. Simulated rainfall experiments were used to generate runoff direct from cowpats. Concentrations of E. coli in the runoff direct from cowpats were found to be directly proportional to the concentration in the cowpat, regardless of the age of the cowpat. It was also observed that E. coli were predominantly eroded from cowpats as individual cells. The interactions between E. coli and soil particles in overland flow were then examined in a small laboratory scale model system and showed that E. coli attached to large (>45 [mu]m) soil particles were transported significantly less than unattached cells. However, in the runoff from the model system, E. coli were found to be attached mainly to clay particles that were similar in size to the bacterial cells. Furthermore, the transport of E. coli through the model system appeared to follow the transport of a conservative chemical tracer implying that (a) the cells were being transported as a solute with the bulk of the water flow, and (b) that E. coli attached to small clay particles were as mobile in the overland flow as unattached cells. These observations imply that E. coli predominantly interact with small clay particles that are also being carried along in the overland flow. The transport of E. coli at a larger scale was then investigated using 5-metre long, 1-metre wide buffer strips operated under saturation excess conditions. In buffer strips using intact soils and existing pasture cover, E. coli removal was very poor (26 % removal) at the low flow rate of 2 L min⁻� with no removal observed at the higher flow rates of 6 and 20 L min⁻�. E. coli removal rates were increased to 41 % removal at 2 L min⁻� by cultivating the soils, with the removal rate again decreasing with increasing flow rate. E. coli in the overland flow from the buffer strips did not form into large flocs or attach to large soil particles, but were transported in small neutrally buoyant particles that remain entrained in the overland flow. Under saturation excess runoff conditions, E. coli in overland flow were not effectively removed by buffer strips as the small particles are transported either over the soil surface or, through large pores in the soil. This Thesis has shown that E. coli is transported in overland flow in small particle sizes that are difficult to trap or remove from overland flow thereby explaining the high fluxes of faecal bacteria observed in overland flow from agricultural land.

Plants produce complex mixtures of secondary metabolites to defend themselves from pathogens. Among these defenses are metabolites produced de novo, phytoalexins, and constitutive metabolites, phytoanticipins. As a counter-attack, pathogenic fungi are able to transform such plant defenses utilizing detoxifying enzymes. This thesis investigates the metabolism of two important cruciferous phytoalexins (brassinin (33) and camalexin (39)) by the phytopathogenic fungus Botrytis cinerea and the metabolism of cruciferous phytoanticipins (glucosinolates and derivatives) by three economically important fungi of crucifers Alternaria brassicicola, Rhizoctonia solani and Sclerotinia sclerotiorum to investigate their role in cruciferous defense. In the first part of this thesis, the transformations of brassinin (33) and camalexin (39) by B. cinerea were investigated. During these studies a number of new metabolites were isolated, their chemical structures were determined using spectroscopic techniques, and further confirmed by synthesis. Camalexin (39) was transformed via oxidative degradation and brassinin (33) was hydrolyzed to indoly-3-methanamine (49). The metabolic products did not show detectable antifungal activity against B. cinerea, which indicated that these transformations were detoxification processes. Camalexin (39) was found to be more antifungal than brassinin (33). In the second part of this thesis, the metabolism of glucobrassicin (86), 1-methoxyglucobrassicin (87), 4-methoxyglucobrassicin (90), phenylglucosinolate (65), and benzylglucosinolate (66), the corresponding desulfoglucosinolates and derivatives by three fungal pathogens (A. brassicicola, R. solani and S. sclerotiorum) was investigated and their antifungal activity against the same pathogens was tested. Aryl iii glucosinolates 65 and 66 were metabolized by A. brassicicola but not by R. solani or S. sclerotiorum, whereas indolylglucosinolates were not metabolized by any pathogen. Indolyl desulfoglucosinolates (159 and 233) were transformed by R. solani and S. sclerotiorum to the corresponding carboxylic acids and indolyl acetonitriles 40, 102, and 103 were also metabolized to the corresponding carboxylic acids by all pathogens. None of the glucosinolates or their desulfo derivatives showed antifungal activity, but some of their metabolites showed low to very high antifungal activities. Among these metabolites, diindolyl-3-methane (113) showed the highest antifungal activity, and benzyl isothiocyanate (170) showed higher inhibitory effect against R. solani and S. sclerotiorum, but did not inhibit the growth of A. brassicicola. The cell-free extracts of A. brassicicola, R. solani, and S. sclerotiorum were tested for myrosinase activity against several glucosinolates. The cell-free extracts of mycelia of A. brassicicola displayed higher myrosinase activity for sinigrin (131), phenyl and benzyl glucosinolates 65 and 66, but lower activities for glucobrassicin (86) and 1-methoxyglucobrassicin (87); no myrosinase activity was detected in mycelia of either R. solani or S. sclerotiorum.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Environmental Sciences." Includes bibliographical references.

Thesis (PhD)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Barry J. Jacobsen. Includes bibliographical references.

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

abstract / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences