Amoebophilus simplex Barron
A spore (conidium) of the fungus sticks to the outer membrane of the amoeba. A narrow peg from this primary attack spore penetrates into the body of the amoeba. A triangular (in section) lobed haustorium (feeding cell) develops from the penetration peg. Food is channeled from the amoeba through the haustorium into the primary attack spore and a branching chain of new spores develops from the outer end of this spore. The living amoeba still feeds and moves around and trails the chain of spores behind it like a tail. Eventually the fungus sucks the amoeba dry and it shrivels up and dies. As it is moving along some of the spores from the chain break off and lie around to attack other individual amoebae. This process is facilitated by the fact that amoebae normally engulf and digest fungus spores as a food source. In is case the tables have been turned and Amoebophilus has evolved to take advantage of this form of predation by amoebae. There are only three species of Amoebophilus known and so probably many more remain to be discovered. They are possibly host specific and the one I found attacked only one of the several species of amoebae present in the original culture.
There is also a sexual stage associated with this fungus that produces zygospores but it is a little too complicated to go into at the moment.