Do we always know when a microbe is eating?

[DonSchaeffer]

Do microbes have a special, recognizable eating behavior? Do they just absorb nutrients helter skelter or is does eating have a special procedure? Can microbes eat on the go while behaving in an undirected way?

[SuiGenerisBrewing]

Depends on the microbe. Bacteria generally acquire nutrients by secreting enzymes that break down food in the environment which is then imported by specialized proteins into the bacteria. Some don't even both with the enzymes and just import what they can.

Most algae photosynthesize and make their own food. That said, they still need to absorb other nutrients from the environment, generally using importer proteins like other bacteria.

Eukaryotes are much more varied. All of them have a process called endocytosis which allows for them to take up small amounts of liquid from their environment, from which they can extract nutrients. Some take this further, and actively engulf whole organisms as prey, digest them in a lysosome (feeding vacuole), and absorb the nutrients. Still others will "stab" prey with needles which then absorb nutrients (again, often by endocytosing the preys innards.

If you include microscopic animals like tardigrades in the category of "microbes", then you have something that feeds more like us - food in engulfed into a dedicated digestive tract, broken down enzymatically, and nutrients absorbed.

[DonSchaeffer]

That is very instructive. Thanks.

[DonSchaeffer]

What do microbes use as "teeth?"

[Alexander]

It depends on the definition of "a".

There are trillions of microbes in the world. At least one of them will eat at any given time. The answer to your question is "yes" so far.

If the intention of your question is, if we always know about any of the trillions of microbes when they are eating, the answer is apparently "no". We can't monitor all microbes currently alive.