Rio San Pedro sediment + 0.3 g paper + 0.1 g CaSO4 + (4 g sugar)
We made two
Winogradsky columns with:
- 40 g Rio San Pedro sediment and 100 g soil.
- 0.3 g paper, whose cellulose will serve as a source of organic carbon for our microorganisms.
- 0.1 g CaSO4, as a sulfur source.
- Rio San Pedro water -note that not any water would do the job, for the osmotic shock would kill our microorganisms- to saturate the mud.
- 4 g sugar in our second column.
Depending
on the metabolism of the different microorganisms found in Rio San Pedro, we
could expect diverse results by the addition of sugar to our Winogradsky column:
- In case there are yeasts -such as Saccharomyces cerevisiae-, some of the sugar we added will undergo alcoholic fermentation, and it’ll be turned to ethanol and CO2. If this happens, it’s likely that the ethanol will be found at the bottom of the column, as this is where -according to the O2 gradient- anaerobic processes can take place.
- On the contrary, if there are other kinds of fermentative microorganisms, such as lactic acid bacteria, it won’t be ethanol but lactic acid what we’ll find -and maybe this could be checked by using spectrophotometric methods-.
- However, another possibility could be the entire degradation and oxidation of the sugar by heterotrophic bacteria, in which case no other metabolic products will be found.
In the column with no sugar, the source of carbon will be much scarcer, and therefore, we forecast a slower growth rate.
Since the
columns will be kept in the dark, we are certain that no phototrophic bacteria
will be able to survive; though we do expect, due to the presence of a sulfur
source, sulfate-reducing bacteria, producers of hydrogen sulfide (H2S).
Do only yeasts use sugar? or do fermentation?
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