A microbiologist is a scientist whose work is the study of very small living things such as bacteria — the field called microbiology. They may work in a hospital lab, a university, a food factory, or public health, asking what a microbe is, how it grows, and whether it can make people sick. The ending -ist means “the person who does this,” the same as in biologist or chemist. So the word is not the study itself; it is the person. It is a formal job title. Though actually, the names sit very close together (microbe, microbiology, microbiological, microbiologist), and that family mix-up is what usually goes wrong, not the science.