Written and maintained by CASRAI Editorial Board
Last updated
General laboratory information, not medical advice. Specimen handling for patient care follows the receiving laboratory’s own instructions.
Short answer
Anaerobic bacteria culture means growing bacteria that cannot divide in the presence of oxygen. It needs two conditions: an oxygen-free atmosphere (a sealed or vented jar, or an anaerobic chamber) and a reduced medium (usually containing a reducing agent such as cysteine). Oxygen exposure during collection or setup is the main reason cultures fail.
Definition and scope
An anaerobic culture is a culture incubated without oxygen so that oxygen-intolerant bacteria can grow. The same idea appears under several names: anaerobic cultures, anaerobic bacterial culture, culturing anaerobic bacteria, anaerobic systems and anaerobic environment. This page covers the research-bench side (atmosphere, media, indicators) and the specimen-handling rules a clinical laboratory publishes for anaerobic collection. It is not a protocol; follow your laboratory’s SOP and the instructions for any product you use.
Genus-level behaviour differs. A laboratory methods unit on Bacteroides states that these bacteria are obligate anaerobes that will not divide in the presence of oxygen, while also noting they are among the most aerotolerant anaerobic species known (Current Protocols, PMC3836205, read 2026-11-07). A clinical laboratory’s collection guidance says that even brief oxygen exposure may be detrimental to anaerobes’ survival (Geisinger Medical Laboratories, read 2026-11-07).
What are the two types of anaerobic bacteria?
The sources read for this page describe anaerobes by how they respond to oxygen rather than by a fixed two-type list. The strict end is the obligate anaerobe, which will not divide in oxygen. Species differ in how long they tolerate exposure, which is why a culture plan is written per organism group rather than for “anaerobes” in general. For the broader oxygen-requirement classes (aerobic, microaerophilic, candle-jar organisms), see our guide on candle jars and when they are used instead of anaerobic jars.
How anaerobic culture is done in practice
Two conditions that must both be met
The Bacteroides methods unit names two fundamental conditions: a relatively low redox potential in the medium, and removal of oxygen from the atmosphere. Redox potential is generally controlled by using freshly prepared medium with a reducing agent, usually cysteine. Because reducing agents have limited capacity, the unit advises using media on the day of preparation unless they are stored under anaerobic conditions, and placing cultures under anaerobic conditions immediately after inoculation.
Atmosphere systems compared
| System | How the atmosphere is made | Reported values |
|---|---|---|
| Sealed jar with gas-generating envelope | Water activates a sodium borohydride tablet to release hydrogen; hydrogen reacts with oxygen on a palladium catalyst in the lid. A sodium bicarbonate/citric acid tablet releases CO2. | CO2 4-10%; suitable atmosphere in about 90 minutes |
| Vented jar | Jar is evacuated and refilled with a premixed gas, with a palladium catalyst removing residual oxygen. | Example mix: N2 85%, CO2 10%, H2 5%; evacuate-and-refill repeated (three cycles in the cited protocol) |
| Anaerobic chamber (glove box) | Gas mix circulated through palladium catalyst filters; materials enter through a purged double-door airlock. | CO2 5-10%, H2 5-10%, balance N2 or argon; O2 below 5 ppm |
Source: PMC3836205, read 2026-11-07. The same unit warns against hydrogen concentrations above 10%, which are explosive and must be carefully monitored.
Common media for anaerobic culture
- BHIS (brain heart infusion supplemented): includes cysteine, hemin and resazurin, with sodium bicarbonate added just before use; TYG is described as an alternative.
- Prereduced chopped meat medium, prepared under nitrogen/CO2 in septum-sealed tubes, as described in the same methods unit.
- Anaerobic transport medium (ATM): a semisolid mineral-salt agar with reducing agents and a chemical indicator, used to carry specimens to the laboratory (Geisinger). See also transport media in microbiology.
General background on plate and broth culture is in our culturing microorganisms guide.
Checking for oxygen exposure: two indicators
Both sources use a colour change as an oxygen check, with opposite colour logic:
| Indicator | Oxygen-free reading | Oxygen present | Where used |
|---|---|---|---|
| Resazurin (about 0.0001% in medium) | Colorless when reduced | Pink/red when oxidised; reported to take about two hours to clear after plates enter a chamber | Research media and chamber checks (PMC3836205) |
| ATM chemical indicator | Remains clear | Turns purple; do not use a tube whose indicator is purple | Transport tubes (Geisinger) |
Where it matters for labs and clinics: specimen suitability
Geisinger Medical Laboratories’ published collection guidance gives a checklist that research readers rarely see:
- Anaerobic transport media are used for collection and transport of anaerobic specimens for up to 72 hours.
- Do not use a transport tube that is opened or damaged, or whose indicator is purple. Store at room temperature, out of sunlight, and observe the expiry date.
- Swabs are not the preferred collection method for anaerobic culture.
- Specimens that usually should not be cultured for anaerobes include coughed sputum, gastric contents, superficial skin and wound material, feces, urine, nasopharyngeal, vaginal, cervical, uterine and seminal specimens, perirectal specimens, BAL, and small bowel contents.
- Fluid up to 5 ml goes into the transport medium; larger volumes (up to 50 ml) are submitted whole in a sterile screw-cap cup.
Because different laboratories set their own rules, the receiving laboratory’s current instructions govern. For aerobic swab cultures, compare throat culture swabs.
What gets rid of anaerobic bacteria?
For obligate anaerobes in the laboratory, oxygen is the limiting factor: they do not divide in its presence, and clinical laboratories treat oxygen exposure as harmful to their survival. The Bacteroides unit adds that these organisms are capable of limited survival outside the mammalian host. This describes culture behaviour only; it is not guidance on treating infection.
Common misunderstandings
- “A candle jar is an anaerobic jar.” It is not; the candle jar is a reduced-oxygen method for other organism groups (see candle jar uses).
- “Anaerobic means any low-oxygen medium.” Both the atmosphere and the medium’s redox state matter, and reducing agents run out, which is why the methods unit advises same-day media use.
- “A swab in an ordinary transport tube is equivalent.” The published collection guidance names anaerobic transport media and states swabs are not the preferred method.
FAQ
What are the two types of anaerobic bacteria?
Sources describe anaerobes along an oxygen-tolerance spectrum. Obligate anaerobes will not divide in oxygen, and some, such as Bacteroides, are unusually aerotolerant.
How many types of culture methods are there?
The methods unit lists four common systems for establishing anaerobic conditions; this page compares the three it describes in detail (sealed jar, vented jar, chamber).
What gets rid of anaerobic bacteria?
In culture, oxygen exposure stops obligate anaerobes dividing. This is not treatment advice.
What are some common media used for anaerobic culture?
BHIS and TYG, prereduced chopped meat medium, and semisolid anaerobic transport media for specimens.
Sources
- Lab Maintenance and Cultivation of Bacteroides Species, Current Protocols in Microbiology, PMC3836205, pmc.ncbi.nlm.nih.gov/articles/PMC3836205, read 2026-11-07.
- Geisinger Medical Laboratories, Microbiology Specimen Collection Instructions: Anaerobic Culture Collection, geisingermedicallabs.com, read 2026-11-07.
