[cmaunder]

Hi guys,

Just need someone to tell me if my logic with this is correct.  Say you have a closed bottle of pure water (for arguments sake - obviously bacteria require more than carbon and water to grow) containing dissolved inorganic carbon (H2CO3 + HCO3 + CO3) and bacteria which use the DIC as a carbon source.  Lets say the starting pH of the bottle is about 5.  As the bacteria grow, they will assimilate the DIC and incorporate some of it into biomass, and respire some of it as CO2.  Since not all of the carbon going into the bacteria, goes back out into the water, there's a net transfer of carbon into the bacteria.  Here's the question... what happens to the pH.  As bacteria take up the DIC, does the pH increase, because they're pulling DIC (and thus H+ ions out of the water, or does it stay the same no matter how much DIC is removed from the water?

Thanks in advance. 

[Borek]

I would say your logic seems correct. What would really happen in the real life situation is much more difficult to predict, as obviously system that can sustain growing bacteria must be also contaminated with other things.