Microbe
Microbe is the shortened form of microorganism that describes any organism that is too small to be seen without magnification. Unlike the word germ, which names “the causative agent or source of a disease, esp. an infectious disease” (OED Online 2020, “germ”), microbe refers to a broader range of microorganisms like bacteria, fungi, and viruses, whether or not they cause disease. In the scientific, medical, and popular lexicon, microbe can describe anything from the “helpful” microbes living in the human digestive tract to the viruses that cause influenza or the common cold.