Why are cyanobacteria unable to grow in acidic conditions, but algae are?

[Fanghur]

Does anyone know why most cyanobacteria are not able to grow in acidic conditions, but algae such as Dunaliella spp. are? They both use chlorophyll, which if I am not mistaken, is acid-labile.

[biojay99]

Cyanobacteria have a thin peptoglycon membrane but no cell wall while algae is a Eukaryotic organism and has a cell wall that is more ridged and able to hold up to acidic conditions. The main thing to take away is the proteins within the kingdom bacteria will denature quicker in a lower Ph while algae in kingdom plantae have a completely different cellular structure that enables them to withstand those extremes better. which is why lemon juice is a common ingredient of organic cleaners because it lowers Ph and prevents bacteria from dividing (though this is not that affective for all bacteria).

[CharonY]

That is partially wrong and partially inaccurate.

All organisms have certain limits to their pH tolerance. Not all algae (which are plants) are low pH tolerant, not all bacteria (such as cyanobacteria) are pH sensitive. What is true is that the physiology of both organisms are so different that one would not expect large similarity in their physiology.

 

Bacteria as well as plant cells have cell walls, which are chemically and structurally very different. The presence of either does not automatically confer pH resistance, though. This is down to other mechanisms but may (in bacteria) also rely on modifications of the outer cell surface.

[Vulgaris]

CharonY is right on that one. You can't make any generalisation towards the pH tolerance of bacteria versus algae. Some acidophilic bacteria have a pH optimum around pH 2, and some can live in solutions of pH 0. But it all comes down to adaptation. Rarely can you take an organism living at one pH and transfer it to an environment with a significantly different pH without either impairing or killing the organism. some bacteria and archaea are quite resistant to this, but it's generally a tough treatment. The thing is, that proteins are typically constructed so to function at the specific pH level the organism live at, and changing the pH much will thus denature this protein, or atleast make it very unstable. This is not the full story, but some of it. Another thing that might affect autotrophic organisms in particular, such as algae and cyano-bacteria, when you change the pH is the concomitant shift in the carbonate equilibrium, which will either increase or decrease the level of CO2 in the water. But there are many more aspects to this. pH is an important controlling factor in all environments.

 

/Vulg