Greetings All !
bergzy ... Sweet !
A couple of lines jumped out at me ...
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Although our studies were confined to the laboratory, we expect them to be pertinent to nature ...
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This is something I always try to be very ...
very ... careful with. Making the jump from lab flask to marine aquarium can be a dangerous thing. Similarly, making the leap with bacterial behavior in freshwater oligotrophic lake systems (there is a TON of research regarding C, N and P limitation in this realm) strikes me as being potentially problematic. Even so, there are valuble clues to be had ... if not definitive answers.
JMO ...
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... exogenously added ethanol is sufficient to enhance bacterial growth; ...
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It's still a little mind-boggling to me that some folks still question whether or not dosing ethanol can increase marine bacterial biomass.
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We reasoned that if ethanol concentration were the primary determinant for enhancement of bacterial growth, then increasing the amount of ethanol produced by yeast should also result in an increase in bacterial growth enhancement up to a certain percentage, ... . Nevertheless, bacterial growth enhancement was ethanol dependent. For example, additional ethanol was produced with between 2 and 4% glucose, and under these conditions bacterial growth was enhanced by 17 to 18% ... . These studies indicate that ethanol is necessary and sufficient to stimulate acinetobacter growth.
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This is an example of one of the pitfalls of trying to project lab research into marine aquarium husbandry. Their use of "bacterial growth" should not be taken as a general assertion ... it's very strain specific.
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Some carbon sources, such as glycerol, which is nonfermentable, require respiration and, thus, result in no ethanol production. YJM835 grown in the fermentable sugars glucose, fructose, or sucrose produced 0.93% ± 0.2% ethanol and enhanced bacterial growth by 53.6% ± 6.3%. Cells grown in glycerol neither produced significant amounts of ethanol (0.03% ± 0.1% ethanol) nor enhanced bacterial growth (−2.54% ± 2.97% growth enhancement), suggesting that yeast-derived ethanol may be the stimulatory component.
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The specific carbon source
matters.
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Low doses of ethanol not only stimulated growth to a higher cell density but also served as a signaling molecule: in the presence of ethanol, Acinetobacter species were able to withstand the toxic effects of salt, indicating that ethanol alters cell physiology.
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There are other things besides increased growth going on with dosing a carbon source.
JMO ... HTH ... nice find.