Real Dictionary

microbe
all the persons inhabiting a country, city, or other specified place [...]
any microscopic organism, esp a disease-causing bacterium [...]
any of the taxonomic groups into which a genus is divided, the members of which are capable of interbreeding: often containing subspecies, varieties, or races. A species is designated in italics by the genus name followed by the specific name, for example
the act of putting together or making up by combining parts or ingredients [...]
the people living in one locality [...]
the state or quality of being active [...]
the study of the relationships between living organisms and their environment [...]
the total number of living organisms in a given area, expressed in terms of living or dry weight per unit area [...]
countable noun: A microbe is a very small living thing, which you can only see if you use a microscope.