It is thermodynamically possible for a prokaryotic microorga

It is thermodynamically possible for a prokaryotic microorganism to oxidize S for energy and electrons, use Fe⁺⁺⁺ as a respiratory electron acceptor, reduce CO₂ for carbon and reduce N₂ for nitrogen, but such an organism is not known to exist. Why? Why can consortia of microorganisms perform energy transduction processes that individual populations cannot? Examples?

Solution

Prokaryotes do not possess membrane bound organells such as mitochondria, nucleus, endoplasmic reticulum, chloroplast, etc. Hence bacteria can not separate metabolically incompatible biochemical reactions in descrete components. Thats why bacteria with all the given features is not known to exist.

The solution to the the problem of compartmentalization is to form association with other organisms with distinct capabilities of carrying out various biochemical ractions. Bacteria can be protected from inhibitory environmental factors such as exposure to hihg level of oxygen. Hense consortia of microorganisms perform energy transduction processes that individual population can not.

Exampe is microbial mat in which anaerobic, aerobic, photosynthetic, sulphte reducing, autotrophic, chemoautotrophic, heterotrophic microorganisms are present.

The uppermost layer of microbial mat is generally dominated by photosynthetic aerobic cynobacteria while the lowest layer is dominated by sulfate reducing anerobic bacteria.