No description available.

The purpose of these experiments was to simulate the passage of water containing protozoans through the condensers of a steam electric station in order to determine the effects upon colonization of downstream communities. For preliminary tests an apparatus consisting of a test cell constructed of acrylic plastic with a small resistance heater controlled by a variable transformer was developed to deliver a heat shock to protozoans while they were being observed through a microscope. Microthermocouples were used to measure the temperature of the fluid in the cell. Response to rapid increase in temperature was determined for the protozoans Euglena gracilis, Spirostomum ambiguum, Colpidium colpoda, Stentor coeruleus, Tetrahymena pyriformis, and Paramecium multimicronucleatum. Response to several constant temperatures was determined for E. gracilis, S. ambiguum, and C. colpoda. In another experiment, water was pumped from an artificial stream through a copper coil immersed in a hot water bath, to produce a 16 - 26°C increase in temperature. The water then flowed in the same manner into a cold water bath cooling it back to its original temperature. The water was then directed into three plexiglass troughs 79 cm. long, 5 cm. wide, and 7.5 cm. high, before it fell over an end plate 4 cm. high back into the artificial stream. Two control troughs were maintained in an identical manner except for the heat shock. The five communities were sampled weekly and records of diversity (i.e. number of species) in each community and estimates of population density of each species were made. The experiment ran for a period of seven weeks. No significant differences in diversity were observed between control and experimental communities. More subtle differences were noticed, however, which indicated that the heat shock may alter the degree to which incoming species can successfully colonize downstream habitats. / Master of Science

Bacteria-protozoa interactions are one of the oldest between prokaryotic and eukaryotic organisms. As such, their study offers a unique opportunity to understand the different relationships that have evolved between them, including pathogenesis, and how their interaction can affect some important processes, such as wastewater treatment. In the first part of the work described here, the grazing defence mechanisms employed by Pseudomonas aeruginosa against the surface grazer, Acanthamoeba castellanii, were investigated. P. aeruginosa cells from early logarithmic growth and stationary phase were found to use different defence strategies. The type-III secretion system (T3SS) was found to be responsible for cytotoxicity of early logarithmic growth cells against A. castellanii. Of the three exotoxins produced by P. aeruginosa PA99, the phospholipase ExoU was found to make the greatest contribution to bacterial toxicity against the amoebae. Interestingly, a PA99null mutant that does not produce any known exotoxins but synthesises a secretion apparatus, was also found to be toxic to the amoeba, suggesting that the T3SS was being used to translocate other unknown toxins. Quorum sensing regulated virulence factor production was found to be involved in the grazing defence response of stationary phase P. aeruginosa cells. A. castellanii was found to be most susceptible to hydrogen cyanide and elastase produced during late logarithmic and stationary phase. In the second part, a stable isotope probing method was developed to investigate carbon flow through bacteria-protozoa food webs in activated sludge. The method was subsequently used to track carbon from bicarbonate and acetate through bacteria-orotozoa food webs under ammonia oxidising and nitrate reducing conditions. It was found that the Peritrich ciliate Campanella umbellaria, dominated the acquisition of carbon from bacteria with access to CO2 under ammonia oxidising conditions. Thus it appears that some of these bacteria must live in the plankton, as C. umbellaria is a filter feeder. No specific protozoan groups were found to dominate carbon acquisition from bacteria with access to acetate, under nitrate reducing conditions, probably due to label dilution. Overall the results presented here showed how bacteria-protozoa interactions have shaped infectious processes in higher eukaryotes, and the dynamics of carbon flow in activated sludge.

Iron is recognized as a key element regulating primary production in large regions of the ocean, but nothing is known of its direct effect on higher trophic levels. Growth and metabolism of two species of heterotrophic protozoans fed iron-rich and iron-poor prey were thus examined. Maximum growth rates of Paraphysomonas imperforata and P. butcheri were observed only when Fe quotas of bacterial prey were greater than 70 $ mu$mol Fe:mol C. At lower Fe:C ratios, but at constant prey biomass (C/ml), both species grew significantly slower. Minimum Fe quotas of the flagellates at these slow growth rates ($ sim$10 $ mu$mol Fe:mol C) were similar to those of iron-limited phytoplankton and bacteria. Growth rate reduction was the result of direct elemental limitation by Fe, judging from the protozoans' positive response to Fe additions and from their biochemical characteristics. Filtration and carbon ingestion rates increased under Fe-limitation, but carbon gross growth efficiency (CGGE) decreased when Paraphysomonas imperforata consumed iron-poor bacteria. Ammonium regeneration efficiency was also reduced. The decrease in CGGE was a consequence of reduced activity of the iron-dependent electron transport system, greater DOC excretion, and greater CO$ sb2$ evolution by Fe-limited flagellates. Paraphysomonas imperforata excreted Fe, even when limited by this element, and retained less of the ingested ration and thus had a higher Fe regeneration efficiency than when consuming Fe-rich bacteria. According to recent measurements of biogenic Fe:C in the subarctic Pacific, our results suggest that heterotrophic bacterivorous flagellates may experience iron-limitation in remote oceanic regions. Such limitation could profoundly affect C, N and Fe cycling in the sea.

Bacteria-protozoa interactions are one of the oldest between prokaryotic and eukaryotic organisms. As such, their study offers a unique opportunity to understand the different relationships that have evolved between them, including pathogenesis, and how their interaction can affect some important processes, such as wastewater treatment. In the first part of the work described here, the grazing defence mechanisms employed by Pseudomonas aeruginosa against the surface grazer, Acanthamoeba castellanii, were investigated. P. aeruginosa cells from early logarithmic growth and stationary phase were found to use different defence strategies. The type-III secretion system (T3SS) was found to be responsible for cytotoxicity of early logarithmic growth cells against A. castellanii. Of the three exotoxins produced by P. aeruginosa PA99, the phospholipase ExoU was found to make the greatest contribution to bacterial toxicity against the amoebae. Interestingly, a PA99null mutant that does not produce any known exotoxins but synthesises a secretion apparatus, was also found to be toxic to the amoeba, suggesting that the T3SS was being used to translocate other unknown toxins. Quorum sensing regulated virulence factor production was found to be involved in the grazing defence response of stationary phase P. aeruginosa cells. A. castellanii was found to be most susceptible to hydrogen cyanide and elastase produced during late logarithmic and stationary phase. In the second part, a stable isotope probing method was developed to investigate carbon flow through bacteria-protozoa food webs in activated sludge. The method was subsequently used to track carbon from bicarbonate and acetate through bacteria-orotozoa food webs under ammonia oxidising and nitrate reducing conditions. It was found that the Peritrich ciliate Campanella umbellaria, dominated the acquisition of carbon from bacteria with access to CO2 under ammonia oxidising conditions. Thus it appears that some of these bacteria must live in the plankton, as C. umbellaria is a filter feeder. No specific protozoan groups were found to dominate carbon acquisition from bacteria with access to acetate, under nitrate reducing conditions, probably due to label dilution. Overall the results presented here showed how bacteria-protozoa interactions have shaped infectious processes in higher eukaryotes, and the dynamics of carbon flow in activated sludge.

No description available.

No description available.

This research was designed primarily to determine whether and to what extent several species of Dipteria (true flies) carry viable dissemules of algae and or Protozoa "in-flight."

This study had a three-fold purpose. First, it was decided to determine if algae and protozoa were emitted to the air at the Denton sewage treatment plant. The information obtained could be of future importance in the fields of algal and protozoan ecology and public health. Second, it was decided to make a survey of the airborne bacteria at this plant. Some researchers have described bacterial air contamination at similar sewage treatment plants, but the one in Denton has not been studied. Third, it was hoped that in this research some relationships could be found between the bacteria and the algae and protozoa in the air in the vicinity of the sewage aeration basin. It was hypothesized that pathogenic bacteria were carried in the air with these other organisms.

This investigation was concerned with three aspects of the problem of passive dispersal of algae and protozoa by aquatic insects: the role of odonates in passive dispersal of viable small aquatic organisms, the passage of viable algae and protozoa through digestive tracts of field-collected herbivorous and carnivorous aquatic insects, and the viability duration of selected algae, during insect transport under monitored conditions.