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.

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