Stringent (obligate) anaerobes can be successfully cultivated if the medium and atmosphere are treated by which special measures?

Introduction / Context: Obligate anaerobes are inhibited or killed by oxygen due to a lack of protective enzymes (for example, catalase, superoxide dismutase). Culturing them requires reducing the dissolved oxygen in media and maintaining an oxygen-free atmosphere during incubation and handling.

Given Data / Assumptions:

• Anaerobes are sensitive to oxygen and reactive oxygen species.
• Media and headspace must be deoxygenated or chemically reduced.
• Handling (inoculation/incubation) should be done in an anaerobic environment.

Concept / Approach: Boiling the medium drives off dissolved oxygen; adding reducing agents (for example, cysteine, thioglycollate) lowers redox potential; and sparging with oxygen-free nitrogen replaces residual oxygen. These steps, used singly or in combination, establish conditions compatible with the growth of stringent anaerobes.

Step-by-Step Solution: Reduce dissolved O2 by heat (boiling) under appropriate safety. Add reducing agents such as cysteine to lower redox potential. Purge headspace with oxygen-free nitrogen to exclude O2. Conclude that any of these measures contributes to successful cultivation.

Verification / Alternative check: Anaerobic jars, glove boxes, and pre-reduced, anaerobically sterilized (PRAS) media apply these principles routinely in clinical and research labs.

Why Other Options Are Wrong: Each single option is correct, but incomplete on its own. The comprehensive answer “any of these” captures the acceptable approaches.

Common Pitfalls: Neglecting rapid transfer and oxygen exposure during inoculation; even perfectly reduced media can fail if handling introduces O2.

Final Answer: any of these.