Talk:Facultative anaerobic organism
|WikiProject Physiology||(Rated Start-class, Mid-importance)|
|WikiProject Molecular and Cell Biology||(Rated Start-class)|
Definition of facultative anaerobe
I think that the more accurate description of an facultative anaerobe would be: A bacteria that is not harmed by oxygen present and can survive without it. In the case of oral streptococci, they are considered facultative anaerobes that do not use oxygen as a final oxidizing agent, as in respiration, to obtain energy from carbohydrates. They use fermentation whether oxygen is available or not. Franky 10:26 4 December 2008
Thioglycollate broth figure
Just a small point on the figure depicting the mode of verifying a bacteria's oxygen requirements- that isn't quite how it works in liquid culture is it? Even if you use a medium like thioglycollate that actually excludes oxygen from diffusing throughout the media, the different densities in cells can't really tell you how they grow best based on where they are as the ability to form visible floating colonies vs. the tendency to precipitate isn't a feature that depends upon oxygen requirements. Would it be wrong to say that this test is usually carried out in solid media in tubes? With an oxygen alerting dye such as methylene blue embedded? The culture growth patterns can then be assessed and position in relation to the methylene blue will indicate oxygen requirements.
At any rate, I think the caption is sufficient in illustrating the point the article is meant to explain, and the illustrations themselves seem to indicate liquid culture so maybe there is a liquid media I am not aware of that would allow for this test.
Hi, I'm provisionally deleting the following section as it appears to contain inaccuracies:
"The concentrations of oxygen and fermentable material in the environment influence the organism's use of aerobic respiration vs. fermentation to derive energy. In brewer's yeast, the Pasteur shift is the observed cessation of oxygen consumption when fermentable sugar is supplied. In a growing culture, the energy "economics" disfavors respiration due to the "overhead cost" of producing the apparatus, as long as sufficient fermentable substrate is available, even though the energy output per mole of fermented material is far less than from respiration's complete oxidation of the same substrate. However, the rate of production of ATP can be up to 100 times faster than that of oxidative phosphorylation. Therefore, tissues and organisms that require fast consumption of ATP preferentially use anaerobic glycolysis."
It is my understanding, for example, that 'Pasteur shift' refers to the observation that aeration increases yeast growth but decreases yeast fermentation. Also, the term 'anaerobic glycolysis' used in the final sentence doesn't make sense. Glycolysis doesn't require oxygen. There's no such thing as 'aerobic glycolysis', is there? What do other people think? Your input would be much appreciated.