In article <01J1EJVAVNLU002F5N at DEPAUW.EDU>, PADAMS at DEPAUW.EDU says...
- A couple of days ago I showed some video of the stromatolites at Shark Bay
-in western Australia. Apparently the cyanobacteria involved give off carbon
-dioxide from aerobic respiration during nighttime. This reacts with minerals
-in the sea water, producing calcium carbonate, which sticks to the slimy
-sheath produced by the cyanobacteria and forms a new layer of the
-stromatolite.
- The student's [excellent!] question: before the evolution of aerobic respiration (about 2 billion years ago) did the cyanobacteria give off carbon dioxide?
-If so, from what process? If not, then how did the cyanobacteria participate
-in forming the layers of the stromatolite>
- Hope some one can help!
-Preston Adams, Biology Dept., DePauw University, Greencastle, IN
-
Great minds or whatever must think alike. I had just prepared the
following to submit to the group when I read your post. Maybe someone
out there can shed some light on this subject. As far as the CO2 is
concerned, fermentation reactions could be responsible as well as aerobic
resp.
While comparing chloroplast, mitochondria, and eucaryote characteristics
today in lecture I stumbled on a question I couldn't answer. Looking at
the energy aspect of eucaryotic cystol - glycolysis/fermentation is the
primary method of ATP generation. And it is my understanding that
advanced anaerobic archaebacteria through the engulfing of aerobic
bacteria resulted in the eucaryotic cell/mitochondria symbiont. This
would mean that there had to be sufficient O2 present for the combination
to work. Now the question is what kind of respiration do cyanobacteria
and similar algae use? aerobic or anaerobic. If the answer is aerobic
this would mean that there must have been an anaerobic pre alga cell that
was able to generate O2 through photosynthesis before the aerobic form.
In other words what came second the pathways for O2 generation or O2
utilization. Unless there was some other mechanism for O2 production it
would appear that O2 generating anaerobes had to come after strict
anaerobes?
