Diferenciacion En Los Amoeboflagelados

Differentiation in the Amoeboflagellate Naegleria

One of the most remarkable cases of protist "differentiation" is that of Naegleria gruberi. This organism occupies a special place in protisttaxonomy because it can change its form from that of an amoeba to that of a flagellate.
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|Figure 1   Transformation from amoeboid to flagellated state in Naegleria gruberi. Top row stained with Lugol’s iodine; bottom row |
|stained with fluorescentantibody to the tubulin protein of the microtubules. Transformation is initiated by rinsing the food |
|(bacteria) from the Naegleria colony. (A) 0 minutes. (B) 25 minutes, showing newtubulin synthesis. (C) 70 minutes, showing emergence |
|of visible flagella. (D) 120 minutes, showing mature flagella and streamlined body shape. (From Walsh 1984.) |During most of its life cycle, N. gruberi is a typical amoeba, feeding on soil bacteria and dividing by fission. However, when the bacteria are diluted (either by rainwater or by water added in anexperiment), each N. gruberi rapidly develops a streamlined body shape and two long anterior flagella, which it uses to find regions of more abundant bacteria. Thus, instead of having severaldifferentiated cell types in one organism, this one cell has different cell structures and biochemistry at different times of its life.
Differentiation into the flagellate form occurs in about an hour.|[pic] |
|Figure 2   Differentiation of the flagellate phenotype in Naegleria. Amoebae thathad been growing in the |
|bacteria-enriched medium are washed free of bacteria at time 0. By 80 minutes, nearly the entire population |
|has developed flagella. (After Fulton 1977.)...