Microbial Oxygen Requirements and FTM (Fluid Thioglycolate Medium)

Obligate Aerobes

Must have O2 to grow/thrive, 21% O2 concentration

Examples of Obligate Aerobes

Mycobacterium tuberculosis (lungs), Micrococcus luteus (skin), Pseudomonas aeruginosa

Obligate Anaerobes

O2 is toxic to these organisms, lacks detox enzymes (catalase, superoxide dismutase)

Examples of Obligate Anaerobes

Clostridium difficile

Facultative Anaerobes

Still thrive in presence of O2, run off of fermentation in anaerobic environment, either lactic acid or alcohol, depending on the organism

Examples of Facultative Anaerobes

E. coli, Salmonella spp., Staphylococcal spp. (including mRSA), Yersinia pestis, Staphylococcus aureus

Aerotolerant Anerobes

Tolerant of oxygen, differ from facultative anaerobes in that these organisms are indifferent to the presence of O2, and use fermentation to grow regardless

Examples of Aerotolerant Anaerobes

Lactobacillus spp. (in probiotics), Streptococcus pyogenes

Microaerophiles

Require just enough O2, not too much, not too little (1-10% O2)

Examples of Microaerophiles

Campylobacter jejuni (associated with GI infection)

What is FTM?

Liquid medium used to determine oxygen requirements of a microbial sample

FTM oxygen gradient

High O2 concentration at top, no O2 at bottom

FTM growth patterns

Obligate aerobe > top
Obligate anaerobe > bottom
Facultative anaerobe > everywhere (top heavy)
Aerotolerant anaerobe > Evenly throughout
Microaerophile > just below top