[@greek_homer]

@greek_homer asked the Naked Scientists:
   
Do microbes live? If so how do they know what they are supposed to do?

What do you think?

[Kryptid]

Many microbes (such as bacteria and yeast) maintain the basic functions of life, such as nutrient consumption, internal chemical regulation, waste removal, reaction to external stimuli and reproduction. They definitely fit the scientific definition of life. Simpler things, such as viruses, do not eat nor reproduce on their own. Whether or not they are "alive" has been subject to debate for quite some time.

Microbes don't have brains the way humans do, so they can't truly "think" about what they are doing. Instead, it might be best to think of them as little pre-programmed machines. They react automatically to certain external cues based on the way they are constructed. For example, if there is a sudden increase in the salt levels (sodium and chloride ions) in their surrounding environment, these ions will diffuse into the cell and cause their cytoplasm to become more saline. Certain parts of the cell's organelles will be designed to react automatically to the increase in salinity. For example, it might set off a chain of chemical signals inside the cell which cause it to move away from the source of the salt (if levels rise too high to control via metabolism).

[WorldOfBiochemistry]

It is important to define what do you mention with "microbes". Protists, bacteria and other unicellular organisms are living organisms, with all the "machinery" necessary to leave and multiplicate. They do not need a host.
However, viruses need a host and, thus, they are not considered a living organism.

Basically, all living organisms perform the same basic things, like eat, develop, multiplicate, etc. Unicellular organisms are not an exception.