About 43,000 bacterial species have names, yet most remain unstudied
Earth holds an estimated two million trillion trillion bacteria, a living mass second only to plants. They were among the first life on the planet. Yet science barely knows them: ten species account for half of all research papers, and around three quarters of named bacteria have never been studied at all.
Bacteria are mostly single-celled, typically a few micrometres long, and live almost everywhere: soil, water, air, acidic hot springs, radioactive waste and deep inside Earth's crust. Their name comes from a Greek word for a staff or cane, because the first ones spotted were rod-shaped, and it was first applied to them in 1828. They were once filed as plants, the fission fungi. They are now classed as prokaryotes, with circular chromosomes and no nucleus. In the 1990s researchers realised prokaryotes actually form two deeply different domains, Bacteria and Archaea.
Their history is the history of life. Bacterial ancestors appeared about 4 billion years ago, and for roughly 3 billion years microbes dominated the planet. Bacteria also shaped the rise of complex cells: eukaryotes arose when ancient bacteria entered partnerships inside the ancestors of those cells, which may have been related to Archaea. Size ranges widely; most are about a tenth the size of a eukaryotic cell, but Thiomargarita namibiensis can reach half a millimetre, visible without a microscope.
They keep ecosystems running, recycling nutrients, fixing nitrogen from the air and driving the putrefaction stage of decay. A human body carries somewhere around 10 to the 13th to 10 to the 14th bacteria, most in the gut. The majority are harmless or kept in check by the immune system, and many gut species help. A minority cause diseases such as cholera, tuberculosis, tetanus, leprosy and plague, and respiratory infections are the deadliest bacterial illnesses. Antibiotic use in medicine and farming has made resistance a growing problem.
The research gap is striking. Escherichia coli, the most studied species, features in more than 300,000 studies, yet about a quarter of its 4,000 genes are poorly understood or uncharacterised.
Source: Bacteria
