It seems common knowledge that Cyanobacteria are nearly absent in acidic environments. I am especially interested in the low abundance of cyanobacteria in acidic soil (~4) compared to eukaryotic algae. Low pH stresses eukaryotic algae as well, anyway they occur in f.e. forest soils with low pH. Do they outcompete cyanobacteria? Or are cyanobacteria not able to cope with low pH - what is the weaker/missing molecular mechanisms compared to eukaryotic algae?
Dear Dr. Karin Glaser
Cyanobacteria, like any other autotrophic prokaryotes rely on a carbon (CO2) concentrating mechanism through the Calvin-Benson-Bassham cycle (CBB) to increase the concentration of inorganic carbon around their primary relevant enzyme, RuBisCO. Because rubisco possesses the dual capability of serving as both carboxylase and oxygenase enzymes, enrichment of CO2 actually triggers higher rates of carboxylation and this downgrades the oxygenation through non-allosteric competitive inhibition. Lower pH means more presence of of the highly permeable H2CO3 in the inorganic carbon pool and forces higher expenditures of energy by the cells to maintain enough of it intracellularly while a higher pH prevents the loss of inorganic carbon.
Because at low pH, the concentration of inorganic carbon always tends to diminish within the cells of cyanobacteria and it requires high energy to maintain inorganic carbon levels as well as the fact that high CO2 concentrations are required by the cyanobacteria as their rubisco has a relartively low carboxylation kinetics, which in essence transcends to more acidic cytosolic conditions triggering more permeability and greater cost of maintenance of inorganic carbon, cyanophyceae do not always favour acidic aquatic conditions in my opinion.
With regards,
Dr. Abhishek Mukherjee
Dear Karin,
we look for algae including lots of cyanobacteria for monotoring according to WRRL in running waters. There ar lots of cyanobacteria in sikiceous waters with low pH. Some species of the genus Chamaesiphon are examples. However the minimum values in our research was 5.1 (see Gutowski et al. 2015): Chamaesiphon species in soft-water streams in Germany: occurrence, ecology and use for bioindication). I think, that there will be also Cyanos from more acidic sites but at the moment I have no concrete data about this. There are sites in Saxony as far as I know.
Greetings Antje
Spyros Gkelis
Thanks a lot for your reply. So far, I focused on the comparision of abundance between eukaryotic algae and Cyanos in soil. Your recommended publication shows that Cyanos can deal with low pH and compete with other bacteria...so maybe in my mesic, acidic forest soils, they are outcompeted by eukaryotic algae.
Abhishek Mukherjee Thanks for your careful explanation! This is a solid reason why Cyanos are less abundant in acidic environments.
Belnap and Lange (2003) reported Green algae (Chlorophyte) are favored on more acidic soils. Areas with alkaline soils and high salt content are favor with Cyanobacteria
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