Microbiology is the study of organisms such as algae, fungi, bacteria and viruses that cannot be seen with the naked eye. These micro-organisms are abundant and diverse, and they affect humans in both negative and positive ways. Some micro-organisms cause diseases in humans, other animals, or agricultural crops. Others can be used to benefit humans, such as microbes that can be used to kill insect pests (biocontrol) and those that destroy harmful chemicals such as pesticides (bioremediation). Other microbes are simply essential to the maintenance of all life, such as those that generate nitrogen, oxygen and other critical elements.

Microbiologists are employed by various industries to test product safety, by wastewater treatment plants to ensure water quality, by hospitals to identify disease-causing microbes, and by research institutes to explore basic aspects of microbial biology, diversity and ecology. The food industry employs many microbiologists for food testing and production of products such as wine, beer, dairy products and mushrooms. Careers can also be in horticulture, plant disease research, terrestrial and freshwater ecology, water pollution investigations and biology teaching.