What does anaerobiosis mean?
Anaerobiosis refers to the state of life or biological activity sustained in the complete absence of free molecular oxygen. It describes both organisms that permanently require oxygen-free conditions — obligate anaerobes such as certain bacteria found in deep sediments, hot springs, and animal intestines — and temporary episodes in which normally aerobic cells switch to oxygen-independent metabolism, as muscle tissue does during intense exertion or yeast does during fermentation. The word derives from Greek roots: 'an-' meaning without, 'aer' meaning air, and 'biosis' meaning mode of life, placing it alongside related terms like aerobiosis and symbiosis. Used almost exclusively in scientific writing, anaerobiosis carries a neutral, descriptive connotation rather than any emotional charge. Its value lies in precision: it names not merely the absence of oxygen but the entire mode of existence built around that absence, a concept central to microbiology, medicine, and the study of Earth's earliest life, which likely arose under anaerobic conditions billions of years ago.
nounLife or biological activity carried on in the complete absence of free oxygen; the condition of an organism that lives and functions without molecular oxygen.
- The condition of living or functioning without free molecular oxygen, as in obligate anaerobic organisms.
- A temporary physiological state induced in normally aerobic organisms when oxygen is unavailable, such as during hypoxia or in sealed environments.
"Certain bacteria survive deep in ocean sediments through anaerobiosis, thriving where no oxygen can penetrate."
"Deep-sea hydrothermal vent microbes rely on anaerobiosis, metabolizing sulfur compounds in water stripped of oxygen."
"During fermentation, yeast cells enter a state of anaerobiosis, converting sugars to alcohol without drawing on atmospheric oxygen."
The plural follows the standard '-sis' → '-ses' pattern of Greek-derived nouns; it appears mainly in scientific literature discussing multiple instances or types of oxygen-free living.
"The survey catalogued diverse anaerobioses across sediment layers at varying depths."
Some microbes have never met a molecule of oxygen in their lives — anaerobiosis isn't a survival trick for them, it's the only way of being alive they've ever known.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of anaerobiosis
Anaerobiosis was formed in the nineteenth century from Greek elements: 'an-' (without), 'aer' (air), and 'biosis' (manner of life). The concept emerged from Louis Pasteur's pioneering work in the 1860s demonstrating that some microorganisms live without oxygen, though the precise coinage of the English term is generally attributed to later scientific usage building on his findings. It shares its roots with cognate scientific terms such as aerobiosis, symbiosis, and antibiosis, all built on the Greek 'biosis'.
Related word forms
How anaerobiosis is actually used
Anaerobiosis is a technical term used chiefly in microbiology, biochemistry, physiology, and ecology; it is rare in everyday conversation. It is typically written in lowercase and takes standard scientific register. The plural form is uncommon but accepted in scientific literature.
Easily confused with anaerobiosis
Aerobiosis is life dependent on free oxygen, whereas anaerobiosis is life sustained entirely without it.
Anaerobic is an adjective describing processes or organisms that function without oxygen, while anaerobiosis is the noun naming the state or condition itself.