Bacteriology is a subdivision of microbiology, focusing on the study of bacteria. Those who specialize in bacteriology are known as bacteriologists. Bacteria are one of the largest domains of microorganisms, among the first life forms to appear on Earth. In any grain of soil, there may be as many as 40 million bacteria cells. Taken together, all of the bacteria on Earth constitute a biomass greater than all plants and animals combined.
Bacteriology emerged alongside the development of the microscope. The first human being to see bacteria was the legendary Dutch scientist Antoine van Leeuwenhoek, who described what he witnessed in water, saliva, and several other substances in the simple microscope he invented. Christian Gottfried Ehrenberg coined the term “bacterium” in 1828. By the late 19th century, scientists such as Louis Pasteur were establishing the connections between bacteria, fermentation, and disease. In the 1880s, Pasteur was bale to immunize animals against bacteria-based diseases, leading to the development of the science of immunology. Both Pasteur and Robert Koch advanced the idea that bacteria cause disease.
In 1910, Paul Ehrlich developed the first antibiotic, earning the Nobel Prize for his revolutionary work. As with most sciences, there are several subdivisions within bacteriology, including soil bacteriology, clinical diagnostic bacteriology, industrial bacteriology, marine bacteriology, hygienic bacteriology, and public-health bacteriology.