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There are facultative anaerobic bacteria that switch to anaerobic respiration in an anaerobic state, but are there any organisms that would still perform anaerobic respiration even when shifted to aerobic conditions? Obligate anaerobes would die when introduced to an aerobic condition right? Are there any which can survive?

This doubt came into my mind while reading the Hugh-Leifson Oxidative Fermentative test. Such a bacterium would be read false positive for oxidisers in such a case because it would ferment glucose even in aerobic conditions.

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    $\begingroup$ There are aerotolerant anaerobes. $\endgroup$
    – WYSIWYG
    Commented Mar 5, 2016 at 7:11

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Are there any organisms that would still perform anaerobic respiration even when shifted to aerobic conditions?

Yes, there are. They are called aerotolerant anaerobes as shown in this figure on tube 5. In the thioglycollate broth, growth is seen throughout the length of the tubeenter image description here

Legend

  1. Obligate aerobe
  2. Obligate anaerobe
  3. Facultative anaerobe
  4. Microaerophilic
  5. Aerotolerant anaerobes

Are there any which can survive?

Obligate anaerobes wouldn't survive in aerobic conditions. Hence they are named so.

Such a bacterium would be read false positive for oxidizers in such a case because it would ferment glucose even in aerobic conditions.

The thioglycollate broth shown here is used to differentiate bacteria into the above said criteria. The Hugh-Liefson test does'nt do that. You can not conclude that a bacteria is aerobic or anaerobic using that test. The H-L test, is interpreted in two ways.

  1. Fermentative - When both the closed tube and open tube show a colour change

  2. Oxidative - Colour change only in the open tube

In short, the words aerobic/anaerobic are not used to interpret the H-L test. But we can draw parallels.

  1. Obligate aerobe - Open tube (+), Closed tube (-) - Oxidative
  2. Obligate anaerobe- Open tube (+ at bottom), Closed tube (+) - Fermentative
  3. Facultative anaerobe- Open tube (+), Closed tube (+) - Fermentative
  4. Microaerophilic- Open tube (+), Closed tube (-) - Oxidative
  5. Aerotolerant anaerobes- Open tube (+), Closed tube (+) - Fermentative
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Yes, for example bacteria that perform lactic acid fermentation are anaerobic but aerotolerant.

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    $\begingroup$ Welcome to BiologySE! do you think you could put some references into your answer? we always appreciate cited references - and it will increase the value of your answer (by allowing others to read more if interested). $\endgroup$
    – Vance L Albaugh
    Commented Aug 31, 2016 at 19:36
  • $\begingroup$ Sorry, I'm new here. Which kind of reference would you prefer? you can find infos about lactic acid bacteria and their fermentation in Brock "biology of microorganisms"'s book. $\endgroup$
    – chocoly
    Commented Sep 2, 2016 at 9:15

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