1) Bacteria 2) Germs 3) Microorganisms 1) Disease-causing bacteria 2) Microscopic living things 
microscopic life forms, particularly bacteria, archaea, protists and viruses. Despite their minute size, they make the greatest contribution to ocean biomass.
Microscopic living organisms, including bacteria, protozoa, and fungi.
microscopic living organisms
Tiny organisms (including viruses and bacteria) that can only be seen with a microscope.
Tiny organisms (including viruses and bacteria) that can only be seen with a 
(Microorganisms) Microscopic living things
Tiny living organisms that can cause fermentation, decomposition or disease.