Typescript (photocopy). / Digitized by Kansas Correctional Industries

In 1971 Strength and Krieg reported the isolation of a floe-forming gram-negative freshwater rod which exhibited large bipolar flagellar fascicles. Despite the intense activity of the fascicles, the organism had appeared unable to swim. However, free-swimming has now been demonstrated within the highly viscous floes formed by the organisms in viscous solutions of gelatin, DNA and methyl cellulose. With each of these viscous agents there existed an optimum concentration for motility. Higher or lower concentrations led to a decrease in motility. In methyl cellulose, strain XI exhibited optimum motility at a viscosity of 200 cp, while strains X and XI were optimal at 10 cp. Nitrogenase activity was demonstrated by the use of the semisolid medium of Döbereiner and Day. No nitrogenase activity occurred when liquid medium was used, and the organisms were obligately microaerophilic in nitrogen-free medium. When (NH₄)₂SO₄ was supplied, no nitrogenase activity occurred and the organism grew best aerobically. The characteristics of strains X, XI and XII indicated that the organisms should be assigned to genus Aquaspirillum. This decision was based on the following considerations: large bipolar fascicles of flagella, a strictly respiratory metabolism, inability to attack carbohydrates, presence of intracellular poly-β-hydroxybutyrate granules, positive reactions for catalase, oxidase and phosphatase, lack of tolerance to 3% NaCl, occurrence of a "polar membrane" in thin sections, and a DNA base composition of 62 to 65% G+C. The strains have been placed in the species Aquaspirillum fasciculus sp. nov. / M.S.

Protection of potable water supplies demands a better understanding of the factors controlling migration of disease causing bacteria in subsurface environments. In this study, the migration behaviour of the waterborne pathogenic microorganisms Escherichia coli O157:H7 and Yersinia enterocolitica was investigated in water saturated granular systems. Both facultative bacteria were grown under aerobic and anaerobic conditions and further acclimatized to a microaerophilic or fully aerated environment for 21 h. Experiments were conducted using laboratory-scale packed columns over controlled extreme dissolved oxygen (DO) concentrations. The observed differences in the transport potential of these pathogens were found to depend strongly on the antecedent growth conditions under the tested environmental settings as well with the environmental DO in certain conditions. Further microbial characterization using cell titrations and FTIR spectroscopy gave a greater insight on the source of the surface charge that was found to dominate the attachment phenomena in sand packed columns. Techniques also revealed a probable role of other cell surface macromolecules (LPS) that could account for non-DLVO behaviour. The results illustrate the importance of considering physicochemical conditions relevant to the natural subsurface environment when designing laboratory transport experiments as evidenced by variations in microbe migration as a function of the DO under growth and acclimation. / Keywords: bacterial adhesion, bacterial transport, DLVO, physicochemical characterization, dissolved oxygen, porous media.

This work explores the effects of body shape and configuration of flagella on motility of Helicobacter pylori, a helical-shaped bacterium that inhabits the viscoelastic gastric mucosa and causes gastritis, ulcers and gastric cancer. Although it is well known that different shapes produce different hydrodynamic drag thus altering the speed and that helical shapes generate additional thrust this has not been quantitatively established for flagellated bacteria. Using fast time-resolution and high-magnification two-dimensional phase-contrast microscopy to simultaneously image and track individual H. pylori and its rod-shaped isogenic mutant in broth and mucin solutions, the shape as well as rotational and translational speed was determined. In collaboration with Professor Henry Fu and Mehdi Jabbarzadeh the experimental data was used to validate the method of regularized Stokeslets by directly comparing the observed speeds to numerical calculations. The results show that due to relatively slow body rotation rates, the helical shape makes at most a 15% contribution to speeds. In order to explore the effects of arrangement of flagella on motility three different Helicobacter spp. were examined: H. suis (bipolar, multiple flagella), H. cetorum (bipolar, single flagellum) and H. pylori (unipolar, multiple flagella) swimming in broth and mucin. Results show that regardless of media, the flagella bundles of bipolar bacteria can assume one of two configurations interchangeably: extended away from the body or wrapped around it. H. suis predominantly swims with the lagging flagella extended behind the body and the leading flagella wrapped around it, but cases where both bundles are extended or both are wrapped have also been observed. In addition the effects of varying pH on motility of H. suis in broth and mucin were investigated. In broth the rotational speed is not significantly affected by varying pH and the peak of the speed distribution shifts to lower values as the pH decreases. However in mucin the rotational speed decreases by a factor of 20 from pH5 to 4 and the motion is completely hindered below pH4. This indicates that H. suis is unable to move below pH4, in agreement with previous findings on H. pylori, due to gelation of mucin below pH4.

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