Using a newly devised model, the in vitro behaviour of E. histolytica strains IP-106, NIH:200 and DKB has been measured. Behavioural differences between the three strains have been demonstrated which correlate with their virulence. Changes in some environmental conditions (e.g. low pH, high concentrations of bile) caused behavioural changes within the strains studied. The type of movement exhibited by trophozoites of E. histolytica have been characterized and the forces produced by a pseudopodium during penetration have been measured. A 'monopodial' form of E. histolytica has been described. This form comprising less than 1% of a normal amoebic population in culture, was found to increase in numbers in the presence of bile and also under conditions of fluctuating temperature. / Iron was found to be a necessary requirement for amoebic growth, having a direct effect on the growth rate of E. histolytica irrespective of the source of the iron (ferric or ferrous). The three strains of E. histolytica investigated exhibited different responses which correlated with their respective virulence.

This thesis attempts to broaden what is known about bacterial symbionts within amoebae by the use of a number of different molecular methods. Initially a number of different amoeba strains were screened for bacterial symbionts by 16S rRNA gene PCR, then the symbionts were identified by comparative sequence analysis and phylogenetic analysis. The amoeba strains containing bacterial symbionts were characterised by cell morphology, 18S rRNA gene sequencing, internal transcribed spacer sequencing and allozyme electrophoresis. Amoebae belonging to the genera Acanthamoeba, Naegleria, Ripidomyxa and Saccamoeba were identified as containing symbionts that belonged to a wide range of different bacterial genera. / Relationships between bacterial symbionts and their host amoebae were analysed by the use of transmission electron microscopy and fluorescent in situ hybridisation using symbiont specific probes. Also described are attempts that were made to isolate and grow the bacterial symbionts outside of their host amoebae as well as experiments to try to transfer bacterial symbionts from one amoeba strain to another. Lastly the results from this study are discussed as a whole to put into perspective how they contribute to the body of knowledge of symbionts within protozoa. / Thesis (PhDAppliedScience)--University of South Australia, 2006.

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Thesis (M.S.)--Marshall University, 2008. / Title from document title page. Includes abstract. Document formatted into pages: contains xiii, 126 p. Includes bibliographical references p. 113-118.

M. Tech. Water care / Free-living amoebae are important predators that feed on bacteria, fungi and algae by phagocytosis. However, a number of bacteria have become resistant to, and are able to survive, grow and exit Free-living amoebae. Free-living amoebae are ubiquitous organisms that have been isolated from various man-made and environmental water systems. Some of these free-living amoebae host amoeba-resistant bacteria such as Legionella spp. Vibrio cholerae and Mycobacterium species which are regarded as human pathogens. The objective of this study was to establish amoebal enrichment and co-culture techniques in order to isolate and identify amoebae and amoeba-resistant bacteria from seeded and environmental water samples. The aim of the study was to introduce and establish amoebal co-culture and amoebal enrichment techniques in South Africa, to provides South African laboratories with baseline information on the efficiency of culture-based methods as well as analytical requirements like incubation temperature, media preparation and storage conditions for amoebal enrichment and co-culture techniques for the detection and isolation of amoebae and amoeba-resistant bacteria from environmental water systems.