When growing microorganisms, several conditions must be considered to ensure successful results including correct temperatures and pH, adequate moisture and sufficient nutrients (such as carbon and nitrogen).

Even experienced microbiologists can run into growth issues with finicky microorganisms. With this in mind, we have created a series of blog posts highlighting a variety of tried and true growth methods for creating an environment best suited for reproduction of various microorganism species.

Method for Obligate Anaerobes

Obligate anaerobes typically live in oxygen-free places, such as in the gut of an animal or in the mud. These sensitive organisms can only tolerate oxygen concentrations of <0.5% to 8%.  Obligate anaerobes metabolize energy using a process not coupled with the consumption of oxygen. If exposed to oxygen, some obligate anaerobes can produce dormant structures called endospores. The endospore is a tough structure that houses the bacteria’s DNA and various other cellular components needed to preserve the cell’s genetic material. If the endospore ends up in an anaerobic environment, it can germinate and the bacterial cell can become active again.

Here are our recommendations to achieve growth success with obligate anaerobes in your laboratory:

Media:  Anaerobic Blood Agar is the best media choice for growing obligate anaerobes. Fresh prepared Nutrient Agar, Tryptic Soy Agar (Soybean Casein Digest Agar), and Standard Methods Agar (Plate Count Agar) are appropriate alternatives for some Clostridium species with an additional period (24 hours) of incubation.

Temperature: 35°C

Atmosphere: Anaerobic

Growth Time: 48 to 72 hours (some obligate anaerobes may require 5 to 7 days to demonstrate sufficient growth)

The following microorganisms can grow using a form of this method (please see our Growth Requirements document for strain specific instructions):

*Most species of Clostridium are obligate anaerobes. However, according to the Manual of Clinical Microbiology, a few strains will give slight growth on solid media incubated under 5% – 10% CO_2^. 

Check out our Growth Requirements for detailed descriptions of all our growth methods.