“How do microorganisms know an organism is dead and it is time to consume them? What stops them from attacking living healthy organisms?” ~ Daryl Albers
This is a great question.
How do worms and micro-organisms know if something is dead for them to eat?
How come earthworms don’t eat healthy plants and roots in the garden?
The answer is they do not know; they just eat!
The degradation of material is done in its simplest form by bacteria.
Bacteria produce enzymes to break down any material around it which it then absorbs and consumes. The enzymes that they produce do not have any sense of what is alive or what is dead; it just does what it does which is to break down a certain material it is designed for.
Then there are micro-organisms higher up in the food chain which feed on these bacteria, such as protozoa. The protozoa in turn are the food source for worms. Worms and other organisms higher up in the food chain also produces their own enzymes to help with breaking down material and feeding.
How come living healthy organisms are not fed on?
To put ourselves in the correct perspective, the truth is our own human body is being fed on every second of the day! We are constantly shedding off dead skin cells, with new cells being made to replace the old ones. Our bodies are constantly being attacked by bacteria, with our immune system constantly protecting us.
The same happens within a wormery system and in a garden. Living organisms (including plants) are constantly creating new cells and have their own immune system which prevents its break down by enzymes and bacterial attack.
However there are times when living organisms can not withstand the attacks and will start to give up and die; this is when you get sick plants and organisms.
Hope this answers your question!