Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, 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 biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationships with plants and animals.

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The world’s largest bacteria is visible to the naked eye

If Bacteria Drink Kombucha, They Stand a Better Chance of Survival on Mars

The largest-known bacterium - a vermicelli-shaped organism that was discovered in shallow mangrove swamps in the Caribbean and is big enough to be seen with the naked eye - is redefining what is possible for bacteria, Earth's most ancient life form.

Giant Bacteria – 5,000 Times Bigger Than Normal – Discovered in Guadeloupe Mangroves

Largest known bacteria in the world are visible to the naked eye

Giant bacteria found in Guadeloupe mangroves challenge traditional concepts

Can we save more lives if we let resistant bacteria live?

Genetic mutations enable efficient evolution of TB-causing bacteria

Wearable Copper Could Protect You Against Bacteria and Viruses

Probiotics Experiment Shows 'Good Bacteria' Can Help Treat Depression

Breeding 2,000 Generations of Bacteria May Have Solved This Major Debate in Biology

Origin of Black Death finally found in bacteria from Kyrgyzstan graves

Mechanism of expanding bacteria revealed

Hunter Gatherer’s Gut Bacteria Might Show History of our Microbiome

Bacteria bred for 2000 generations settle long-term evolution mystery

Research sheds light on how bacteria communicate their way to causing infection

Designing protection suits for hard working bacteria

IgG antibodies in breast milk help shape infants' gut bacteria and immunity

'Good' bacteria to tackle depression

How fast-growing bacteria can resist antibiotics