Endosymbionts of Protozoa

Endosymbionts of Protozoa

	Endosymbionts of protozoa Here algae and protozoa exhibit mutualism. Paramaecium hosts Chorella within its cytoplasm. Presence of Chlorella allows the protozoan to move into anaerobic habitats as long as there is sufficient light. Similarly the foraminiferans (protozoa) lodge Pyrrophycophycean members (red algae) within their cells. The algae impart red colour to the protozoans and each protozoan can contain about 50-100 algal cells. Fresh water protozoans usually lodge chlorophycean members within themselves and are known as zoochlorellae. Similar marine protozoan partners are Dinoflagellates which lodge chrysophycean members and are known as zooxanthellae
There are a few bacterial symbionts within protozoans. There is a unique relationship between Paramaecium aurelia and Caedibacter. Paramaecium aurelia exhibits two kinds of cells, one type called killer cells (contain endosymbionts, i.e. the Caedibacter whose cells contain an inclusion body called R body which is a toxin) and the other kinds are the sensitive cells. These killer cells compete with the sensitive strains (those devoid of the endosymbiont) for their survival. Endosymbiotic methanogens have been found in anaerobic ciliate protozoans living within the rumen, for example, Methanobacterium, Methanocarpusculum and Methanoplanus. They facilitate material exchange between the protozoan members and the bacteria.
Interaction of temperate phage and bacterial population Genetic influence of phage particles incorporated within the genome of bacterial population (lysogenic phages) provide a mechanism of survival for the phage in a dormant stage for a long period. Bacteria harbouring lysogenic phages exhibit greater virulence. It also provides a mechanism for genetic exchange of bacterial DNA (transduction)

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