Microbiology
Microbiology (from Greek , "mīkros", "small"; , "bios", "life"; and , "-logia") is the study of microorganisms, those being unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virology, parasitology, mycology and bacteriology.
Microbial population biology
Microbial population biology can (and often does) involve the testing of more-general ecological and evolutionary hypotheses. Again, it is important to retain some emphasis on the microbe since at some point this "question-driven" microbial population biology becomes instead population biology using microorganisms. Because the point of departure of these potentially disparate emphases can be somewhat arbitrary, there exist vague and not universally accepted delimits around what the discipline of microbial population biology does and does not constitute.