Tony, Westcliffe asked:
Do bacteria have intelligence? How do they find their food?
Bacteria have no brain, but on the surface of a bacterial cell there are receptors for different chemicals. This means that they can tell which way to travel by comparing, chemically, how many of those receptors have things that they like - or dislike - attached. They assume that the side with the most ‘good’ receptors filled is closest to their food. They use this as a guidance mechanism to control where they go.
Bacteria travel towards desirable chemicals, or away from toxic ones, using a tail called a flagellum. This is like a propeller, powered by a protein ‘motor’.
When the ‘motor’ burns energy it causes the protein to change shape, quickly spinning the long ‘tail’ part.
This lets bacteria move so quickly that one species - Bdellovibrio - are officially the world's fastest swimmers, travelling up to sixty times their body length in each second!
Communities of bacteria also employ decision-making processes involving quorum sensing, where each bacterium produces and emits signaling molecules, and in turn, senses those signaling molecules from other bacteria and modifies its gene expression and/or behavior based on the levels that it senses. In this way, bacteria can behave as one organism based on the size of their community.
As so often happens, it all depends on your definition of intelligence.
Chemotaxis is sometimes described as simple stimulus response mechanism. A causes B. But it actually is more complex.