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I'm not a microbiologist, but rather a physiologist curious about microbial metabolism. Much like humans bacteria can utilize glucose, but when it comes to long chain, medium chain, or short chain fatty acids, what are the pathways that microbes use to break these compounds down for fuel?

It seems plausible that bacteria can take up short chain fatty acids, but with longer chain species are there impediments to uptake? Are the oxidative enzymes similar between bacteria and humans?

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    $\begingroup$ Beta-oxidation happens in mitochondria. So there is a good reason to assume that bacteria can metabolize fatty acids. $\endgroup$
    – WYSIWYG
    Commented Mar 5, 2016 at 7:09
  • $\begingroup$ I don't see the connection between bacteria and mitochondria. Bacteria don't have mitochondria. If you are referring to the endosymbiosis theory, mitochondria are likely descendants of archaea, not bacteria. $\endgroup$
    – Thawn
    Commented Mar 7, 2016 at 14:07

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I found this review about bacterial lipid metabolism. There it says:

Exogenous long chain fatty acids are utilized by E. coli in two ways. Firstly, they can be incorporated into the membrane phospholipids by the acyltransferase system (PlsB and PlsC; Section 4). Secondly, they can be used as the sole carbon source for growth, and are in fact an important source of energy for E. coli in their normal habitat, the intestine [16]. The CoA thioester of the fatty acid is the substrate for both of these pathways. Fatty acids greater than 10 carbons in length require the fadL gene product to be taken up from the growth medium in sufficient quantities to support growth.

So yes, bacteria can grow on fatty acids alone and they can utilize long fatty acids as an energy source. However the uptake of the long fatty acids requires the protein produced by the fadL gene.

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  • $\begingroup$ +1 that's a great review included in your answer. I was mostly interested in whether or not bacteria could use triglyceride as fuel because I was unsure if they expressed a lipase to break down the triglyceride to individual fatty acids (like pancreatic lipase produced by humans for lipid digestion). I wanted to start by trying to understanding if there were limitations to fatty acid metabolism. However, in that review it states that some bacteria do express an outwardly directed, membrane-bound lipase for that purpose. Very cool! $\endgroup$
    – Vance L Albaugh
    Commented Mar 5, 2016 at 16:07
  • $\begingroup$ Glad I could help :-) $\endgroup$
    – Thawn
    Commented Mar 7, 2016 at 14:04
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I wanted to start by trying to understanding if there were limitations to fatty acid metabolism.

There are aerobic bacteria that can reduce fatty acids. However, there are no bacteria that reduce fatty acids without any oxygen equivalent to, say, fermantation (sugar->alcohol).

You can try this in the lab or even at home. Put tomato purée or sugar in a bottle. Put a layer of oil above it. Keep one bottle open and the other one closed (air-tight). You'll see that the bottle that is open will get molded while the closed bottle will not. This is because there are no bacteria that can penetrate the layer of oil because there are no enzymes strong enough to work anaerobically.

Also, good tip to preserve your food at home.

Source: I'm a biotech engineer. Carlson, Karin; Linder, Claes et al.

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