LAB 2 - Oxygen Requirements of Bacteria Flashcards
Microaerophiles
Require oxygen at low levels for growth but are damaged by atmospheric oxygen
Further subdivisions of anaerobic bacteria
- Facultative anaerobes (do not require oxygen for growth but grow better in its presence)
- Aerotolerant anaerobes (not sensitive to presence or absence of oxygen)
- Obligate/strict anaerobes (do not tolerate O2 and die in its presence)
Thioglycollate broth
- Useful for investigating the relationship of a microorganism to oxygen
- Made up of three components that act to reduce total amount of oxygen in the medium
Three components of Thio broth
- Thioglycollic acid
- Cystine
- 0.075% agar
Thioglycollic acid and Cystine
Both reducing agents that chemically react with O2 and reduce it to H2O
0.075% agar
Acts to slow the diffusion of o2 in the medium
Resazurin dye
- Added to Thio broth as indicator of amount of o2 in medium
- red in presence of o2, colourless under anaerobic conditions
Purpose of steaming Thio broth before use
Removes all oxygen from tubes
Incubation and inoculation of Thio broth
- Oxygen is able to diffuse into the top part of the medium and support the growth of aerobic organisms,
- Bottom part of the medium remains devoid of oxygen and
supports the growth of anaerobic organisms.
Inoculation technique used for Thio broths
Stab inoculation all the way to the bottom of the tube
T/F: The lids of a Thio broth are not screwed down tightly
TRUE
Describe the relationship of Clostridium sporogenes to oxygen.
Strict anaerobe, forms endospores in presence of oxygen
Describe the relationship of Pseudomonas aeruginosa to oxygen.
facultative anaerobe
List THREE ways of culturing strict anaerobes in the laboratory (other than THIO broth)
- Anaerobic chamber
- Gas-Pak System
- Reducing media/rolling culture
