Abstract

Microbiology is the study of organisms which are small enough to require the aid of a microscope to be seen. In a few cases, organisms are included in this group, which can be seen by the unaided eye because these organisms are clearly related to the smaller ones. Microorganisms include viruses, bacteria including rickettsia, mycoplasma, fungi (yeast and molds), most algae, protozoa and, if one interprets “micro” broadly, certain tiny multicellular plants and animals. The study of cells and tissues from higher plants and animals (tissue culture) uses techniques common to the microbiologist and is frequently considered part of modern microbiology.