Amoebas

This appeared in the January 20, 2022 edition of The Fish Wrap.

In our exploration of the soil food web, we recently talked about ciliates and flagellates. Today we turn to their fellow Protozoa, the Amoeba. The name Amoeba comes from the Greek verb ‘to change’ and they sure do change. An amoeba doesn’t have any particular shape or appendages. They move by extending a part of themselves and eat by surrounding their food and absorbing it. Their food source may include bacteria, plant cells, dead organic material, algae and other protozoans.

Amoebas don’t have cell walls, which allows for free movement. They may decide where to move by communicating with other amoeba through chemical signals. A startled amoeba will change its body into a star shape, though it’s not nice to sneak up on them. Amoebas even use dramatic change for reproduction. Every two days, an amoeba splits into two bodies, which are clones.  

Finding a healthy population of amoebas tells you that you have highly functioning soil. Soil amoebas roam the film of water coating each soil particle. A single amoeba can eat thousands of bacteria each day. They don’t use all of the nutrients in the bacteria they eat, so their waste contains lots of nutrients that are available for uptake by plants that need them to thrive. Predatory amoebas feast on bacteria and pathogens that are harmful to plants, controlling their population. 

A type of amoeba with the unfortunate name of ‘slime mold’ is a startling organism to find in your garden. When all is well, slime mold amoebas exist as single-celled organisms, feasting on rotting vegetation. But when food becomes scarce, they signal to their brothers and move together to form a billion amoeba mass, reconfiguring themselves to form stalks containing spores. The spores get picked up and moved to greener pastures by wind or passing animals.