Monoxenic and axenic cultivation of carrier and patient strains of Entamoeba histolytica

Giant cells: multiple cells unite to survive

Multinucleated Giant Cells (MGCs) are specialized cells that develop from the fusion of multiple cells, and their presence is commonly observed in human cells during various infections. However, MGC formation is not restricted to infections alone but can also occur through different mechanisms, such as endoreplication and abortive cell cycle. These processes lead to the formation of polyploid cells, eventually resulting in the formation of MGCs. In Entamoeba, a protozoan parasite that causes amoebic dysentery and liver abscesses in humans, the formation of MGCs is a unique phenomenon and not been reported in any other protozoa. This organism is exposed to various hostile environmental conditions, including changes in temperature, pH, and nutrient availability, which can lead to stress and damage to its cells. The formation of MGCs in Entamoeba is thought to be a survival strategy to cope with these adverse conditions. This organism forms MGCs through cell aggregation and fusion in response to osmotic and heat stress. The MGCs in Entamoeba are thought to have increased resistance to various stresses and can survive longer than normal cells under adverse conditions. This increased survival could be due to the presence of multiple nuclei, which could provide redundancy in case of DNA damage or mutations. Additionally, MGCs may play a role in the virulence of Entamoeba as they are found in the inflammatory foci of amoebic liver abscesses and other infections caused by Entamoeba. The presence of MGCs in these infections suggests that they may contribute to the pathogenesis of the disease. Overall, this article offers valuable insights into the intriguing phenomenon of MGC formation in Entamoeba. By unraveling the mechanisms behind this process and examining its implications, researchers can gain a deeper understanding of the complex biology of Entamoeba and potentially identify new targets for therapeutic interventions. The study of MGCs in Entamoeba serves as a gateway to exploring the broader field of cell fusion in various organisms, providing a foundation for future investigations into related cellular processes and their significance in health and disease.

Pleiotropic phenotype in Entamoeba histolytica overexpressing DNA methyltransferase (Ehmeth)

The protozoan parasite Entamoeba histolytica expresses a cytosine-5 DNA methyltransferase (Ehmeth) that belongs to the Dnmt2 proteins family. The biological function of members of the Dnmt2 family is unknown. Constitutive overexpression of Ehmeth resulted in a pleiotropic phenotype that includes accumulation of multinucleated cells, upregulation of Heat shock protein 70 (HSP70) expression and resistance to oxidative stress. This pleiotropic phenotype suggests that Ehmeth plays an important role in the control of key cellular processes in the parasite.

Axenic cultivation of Entamoeba dispar Brumpt 1925, Entamoeba insolita Geiman and Wichterman 1937 and Entamoeba ranarum Grassi 1879

Three species of Entamoeba have been grown in axenic culture for the first time. In two cases, novel methods for adapting the organisms to growth without bacteria were employed. While E. ranarum was axenized by the classic technique of Diamond, from a monoxenic culture with Trypanosoma cruzi as the associate, both E. dispar and E. insolita were first grown in axenic culture medium supplemented with lethally irradiated bacteria. From there, E. insolita was axenized directly, but E. dispar initially required the presence of fixed bacteria. After prolonged culture under this technically axenic but unwieldy culture system, E. dispar was eventually adapted to growth in the absence of added bacteria.

A light and electron microscopical study of a new, polymorphic free-living amoeba, Phreatamoeba balamuthi n. g., n. sp

A new amoeba, isolated from well water in Gambia, West Africa, is described and named Phreatamoeba balamuthi n. g., n. sp. Requiring anaerobic conditions for growth, it is easily cultured monoxenically with Escherichia coli or axenically in complex, undefined organic media. Three phenotypes have been observed in the life cycle: an amoeba, a flagellate, and a cyst. The amoeba moves by monopodia, is predominantly multinucleate, and varies from 11 to 160 microns in length. The flagellate has a single flagellum and is from 6 to 50 microns long. The cyst is surrounded by a resistant wall that lacks pores and ranges from 9 to 18 microns in diameter. The transformation from amoeba to flagellate can be induced nutritionally, the exact inducing factor(s) being unknown. Sexual reproduction has not been observed.

Genetic control of susceptibility of mice to infection with E. histolytica

Genetic susceptibility to Entamoeba histolytica infection in nine inbred strains and one outbred strain of mice was studied. The number of E. histolytica trophozoites in the ceca of the mice was examined 5 days after intracecal inoculation of axenic amoebae. C3H/HeCr, BALB/c, NZB/BIN, B10.A, DBA/2 and C57BL/6 were susceptible whereas A/J, CE, DBA/1 and CD-1 mouse strains were relatively resistant. Examination of F1 hybrid animals derived from susceptible B10.A and resistant A/J strains of mice showed that susceptibility was dominant over resistance. Segregation analysis of backcross and F2 progeny derived from the same progenitor strains is compatible with the hypothesis that susceptibility to E. histolytica infection in mice is controlled by a single, dominant gene which has been designated Enh. No association was found between the H-2 haplotype and the trait of susceptibility to amoebiasis, indicating that the major histocompatibility complex does not play a major role in regulating the early phase of the response to infection with E. histolytica.