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Is gas produced by bacteria always mainly methane? Or, are there bacteria out there that produce some biogas composed mainly of hydrogen, natural gas, propane, butane?

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synthetic biology is working hard to produce such things, but they aren't found naturally in significant quantities I think. – shigeta Feb 24 '13 at 4:59
note that methanogens actually use $H_2$ that is generated by other bacteria. – mart Feb 25 '13 at 12:10
up vote 6 down vote accepted

Microbes can produce several gasses other than methane.

  • All microbes produce $CO_2$ through the oxidation of reduced carbon

Additionally some metabolic pathways produce other gases.

  • Photosynthetic microbes produce $O_2$

  • Sulfur reducing bacteria can produce $H_2S$ (as @ohcanada points out)

  • Denitrifying bacteria produce $NO$, $N_2O$, and $N_2$

  • Fermenters produce $H_2$ (as @mart indicates)

There may be others that I am not thinking of but these are some of the major players...

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Good answer. Although fermentation can produce carbon dioxide too. – Jack Aidley Feb 25 '13 at 13:38
@JackAidley indeed they do... thanks. I edited the answer. – KennyPeanuts Feb 25 '13 at 14:40

Well, some bacteria can produce Hydrogen Sulfide gas. For example, Proteus and Salmonella. The presence of $H_2S$ producing bacteria is actually clinically significant and we have a way to test for this, which is via the use of TSI (Triple Sugar Iron) media.

Assume you set up the test correctly, $H_2S$ producing bacteria will generate dark deposit within the media.

In the clinical setting, there are other choices beside TSI, such as SIM media and API20E.

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Thanks sviter! This is actually my first time using Stackexchange so I'm still trying to familiarize myself about the word format here. – ohcanada Feb 24 '13 at 15:05

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