Includes bibliographical references (leaves 274-318) Cryptic plasmids from ruminal strains of Bacteroides ruminicola and Selenomonas ruminantium were isolated.

The purpose of this investigation was to compare some of the properties of a spore-forming mutant of Bacillus cereus 569R with the wild type. The strains were grown under identical conditions in liquid medium. The mutant, strain 45, was characterized with respect to growth rate, pH changes in the medium, morphological development, cell density during the growth cycle, the effect of oxygen deprivation on the time of spore formation, and the production of an extracellular protease. Strain 45 was found to maintain a higher growth rate than 569R. The pH curves indicated that, in time, strain 45 was about 30 minutes ahead of wild type. Morphologically, strain 45 exhibited no long chain stage characteristic of early logarithmic growth B. cereus 569R. Poly β hydroxybutyrate was accumulated before the sharp rise in pH in 45. This comparatively early synthesis suggested that acetate utilization and polymer synthesis may not be coordinately controlled in this mutant. Spore formation occurred two and one-half hours earlier in strain 45, and the spores were twice as large as spores of wild type. The production of protease in the mutant occurred earlier, and in higher concentration when compared with 569R. The results of these experiments fell into two classes. The first class included growth rate, pH, and cell density shifts. These events occurred approximately one-half hour earlier in cultures of strain 45, and appeared to be correlated with the cell mass. The second class of results--the time of polymer synthesis, the period when the time of sporulation was sensitive to oxygen, the time of protease production, and the time of sporulation- - appeared to be independent of cell mass, and occurred markedly earlier in strain 45. The very early appearance of these sporulation- related events in the culture cycle suggested that the mutant strain 45 may be catabolically derepressed for sporulation. Characterization of two asporogenous mutants of B. cereus 569R was also undertaken. / Graduation date: 1970

Starved cells of Ant-300, a psychrophilic marine Vibrio, maintained binding and transport systems for glutamic acid, arginine, proline, and leucine. The uptake of these amino acids was inhibited by the uncoupler 2,4-dinitrophenol indicating that an energized membrane was necessary for binding and was maintined in starved cells. The levels of macromolecular synthesis and CO₂ production decreased after the cells had starved for 24 hours and remained low for 30 days of starvation. Most of the amino acid taken up by starved cells was held in shock releasable pools. The substrate affinity of the leucine and arginine binding proteins increased after 48 hours of starvation while the velocity decreased. These starvation induced changes remained constant throughout the 20 day starvation time of the experiment. The maintenance of binding proteins and an energized membrane by a starved cell which has no energy input means that the cell is not committed to total inactivity. The survival form is more of a 'ready and waiting' form, capable of maintaining itself in an unfavorable environment while retaining the ability to take advantage of any favorable shift in its surroundings. / Graduation date: 1981

YscD is an essential component of the plasmid pCD1-encoded type III secretion system (T3SS) of Yersinia pestis. YscD has a single transmembrane (TM) domain that connects a small N-terminal cytoplasmic region (residues 1 to 121) to a larger periplasmic region (residues 143 to 419). Deletion analyses demonstrated that both the N-terminal cytoplasmic region and the C-terminal periplasmic region are essential for YscD function. Additional studies demonstrated that a predicted cytoplasmic forkhead-associated (FHA) domain of YscD is also required for function; in contrast, a predicted periplasmic phospholipid binding (BON) domain and a putative periplasmic "ring-building" domain of YscD could be deleted with no significant effect on the T3S process. Although deletion of the putative "ring-building" domain did not disrupt T3S activity per se, the calcium-dependent regulation of the T3S apparatus was affected. The extreme C-terminal region of YscD (residues 354 to 419) was essential for secretion activity and had a strong dominant negative effect on the T3S process when exported to the periplasm of the wild type parent strain. Finally, replacement of the YscD TM domain with a TM domain of dissimilar sequence had no effect on the T3S process, indicating that the TM domain has no sequence-specific function in the assembly or function of the T3SS.

Effective detection of bacterial pathogens in large sample volumes is a challenging problem. Pre-concentration routines currently in practice before the actual detection process are cumbersome and hard to automate. An effort is made to address the problem of volume discrepancy between day-to-day samples and the concentrated samples needed for analysis. Principles of conceptual design are used in formulating the ‘Need Statement’, ‘Function Structure’ and in identifying the ‘Critical Design Parameters’ and ‘Design Constraints’. Electrokinetic phenomena are used to exploit the surface charges on bacteria. Electrophoresis is used to transport the bacteria to electrode surface and “Electrostatic trapping” is then used to capture these microbes on the electrode surface. The captured microbes can then be concentrated in a concentrator unit. A prototype microfluidic device is fabricated for showing the proof of concept. Optimization is done to minimize hydraulic power consumption and wetted volume. Observations from the initial prototype device along with the optimization results are used in building a new prototype device. Operation of this device is demonstrated by capture of bacteria from flow. Qualitative studies are conducted and preliminary quantification is also done.

Effective detection of bacterial pathogens in large sample volumes is a challenging problem. Pre-concentration routines currently in practice before the actual detection process are cumbersome and hard to automate. An effort is made to address the problem of volume discrepancy between day-to-day samples and the concentrated samples needed for analysis. Principles of conceptual design are used in formulating the ‘Need Statement’, ‘Function Structure’ and in identifying the ‘Critical Design Parameters’ and ‘Design Constraints’. Electrokinetic phenomena are used to exploit the surface charges on bacteria. Electrophoresis is used to transport the bacteria to electrode surface and “Electrostatic trapping” is then used to capture these microbes on the electrode surface. The captured microbes can then be concentrated in a concentrator unit. A prototype microfluidic device is fabricated for showing the proof of concept. Optimization is done to minimize hydraulic power consumption and wetted volume. Observations from the initial prototype device along with the optimization results are used in building a new prototype device. Operation of this device is demonstrated by capture of bacteria from flow. Qualitative studies are conducted and preliminary quantification is also done.

Thesis (M. Med. Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 26-35).

Thesis (Ph. D.)--University of Rhode Island, 2003. / Typescript. Includes bibliographical references (leaves 162-173).

abstract / Biological Sciences / Doctoral / Doctor of Philosophy

Antibiotic resistance profiles and the correlation of enteric bacterial pathogens from HIV positive individuals with and without diarrhoea and their household drinking water were determined using the Kirby Bauer disk diffusion and polymerase chain reaction methods respectively. The sef gene of Salmonella enteritidis was amplified with the primer pair sefA-1 and sefA-2. The fliC gene of Salmonella typhimurium was amplified with the primer pair flicA-1 and flicA-2. Heat-labile toxin (LT) primers (Lta and LTb) were used to amplify Escherichia coli isolates and VirA1 and VirA2 for the Vir A gene of Shigella dysenteriae. Results of antibiotic resistance profiles of enteric bacterial pathogens isolated from stool samples of HIV positive and negative individuals with and without diarrhea and their household drinking water showed very similar drug resistance patterns. Over 90% of all the organisms isolated from the various study cohorts showed resistance to penicillin, cloxacillin and amoxicillin. Conversely, almost all the organisms were sensitive to ciprofloxacin, gentamycin, meropenem and imipenem. About 50% of E. coli isolated from the various study cohorts showed multiple antibiotic resistance to penicillin, amoxicillin, ampicillin, erythromycin, tetracycline, doxycycline and cotri-moxazole ( PR, AR, APR, ER, TR, DXTR, and TSR ) whereas less than 10% resistance was consistently reported for ofloxacin, gentamycin, meropenem cefotaxime, cefuroxime and imipenem ( OFXS, GMS, MEMS, CTXS, CXMS and IMIS ). The majority of Salmonella and Shigella isolates from all the groups were sensitive to ciprofloxacin, gentamicin, amikacin, meropenem, imipenem, nalidixic acid, kanamycin, piperacillin-tazo bactam, cefuroxime, doxycyclin, cefepime and ceftazidime (CIPS, GMS, AKS, MEMS, IMIS, NAS, KNS, DXTS, CXMS, CPMS, CAZS and PTZS). For Campylobacter, over 30% of the isolates were resistant to erythromycin, ampicillin, tetracycline, cotrimoxazole and ceftazidime (ER, APR TSR and CAZR) whereas over 85% were susceptible to ciprofloxacin, ofloxacin, gentamycin, amikacin, mero-penem, and nalidixic acid (CIPS, OFXS, GMS, AKS, MEMS and NAS). In addition to penicillin, amoxicillin, ampicillin and erythromycin, Aeromonas and Plesiomonas spp were more resistant to chloramphenicol, but were susceptible to ciprofloxacin, gentamycin, amikacin, meropenem, imipenem and nalidixic acid (CIPS, GMS, AKS, MEMS, IMIS and NAS). Polymerase Chain Reaction (PCR) experiments using targeted species genes of S. enteritidis, S. typhimurium, E. coli, Sh. dysenteriae showed that isolates from stool samples of HIV positive and HIV negative individuals with and without diarrhoea were also present in the household drinking water of the same study cohorts, suggesting that drinking water may have been the sources of the organisms in stool sample. Furthermore, by showing that the primers were able to amplify the genes in both clinical and environmental isolates, the link between the virulence of the pathogens was established