Question

you are not sure if an organism is an obligate aerobe or a facultative anaerobe. If you do not have an anaerobe jar,how could you identify the oxygen preference for the organism?

Answer 1

Different requirements of molecular oxygen of a bacteria can be observed by using thioglycolate tube cultures.
1.Firstly we take an autocaved thioglycolate medium (autoclaving is necessary to flush out the oxygen) with a little agar for the movement of bacteria throughout the medium.
2.Now tubes are inoculated with all the possible bacterial cultures that are present at a suitable temperature
3. Oxygen diffusion is observed gradually from thioglycolate culture tube's top
4. bacteria grows in the area where there is availability of oxygen
Observation:
a) When bacteria grows on the top of the tube we know it's an aerobic bacteria and can't grow without availability of oxygen. (Tube A)
b)If bacteria grows at bottom of tube they are obligate anaerobes as presence of oxygen will kill them . (tube B) the bacteria.
c) If heavy growth of bacteria is observed at the top of the tube and throughout then it is said to be a facultative anaerobes (grow in presence of oxygen also but can also live in it's absence on products of anaerobic respiration) (tube C)