Bacteria is a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth’s crust. Bacteria live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

Bacteria ruled the world for three and a half billion years before humans even made an appearance. They continue to rule the world today. The truth is, we live in a microbial world, and not the other way around.

In fact, there are 38,000,000,000,000 of them living in and on you right now. They make up your microbiome and are essential to your health, performing functions like aiding in digestion, modulating immune responses, and producing vitamins and key metabolites.

Bacteria have historically had a bad rap—the discovery of some pathogenic ones like Mycobacterium tuberculosis and Escherichia coli sent us into germ hysteria, resulting in a century of antibiotic and antibacterial overuse, attempting to wipe them out of existence.

We now know that the overwhelming majority of bacteria are benign, and many are even beneficial, if not essential. It’s time we started taking care of them.