what do anaerobic bacteria eat ?

[MCsaxmaster]

Time to lose my infatuation with diffusion across concentration-depleted boundary layers & biological alteration of boundary layers (which was really my whole point) as the determinant variables regulating nutrient uptake.

Ha, okey dokey

Have either of you come across studies or papers postulating what advantage cyanobacteria gains by growing in sheets? I have often wondered if this is some sort of nutrient sequestering strategy ie: sheet over your nutrient source before something else grows to take advantage of it.

One of the postulated advantages has to do with the efficiency of N-fixation. Nitrogenase activity is sensitive to oxygen concentration. Nitrogenase becomes ineffecient with elevated O2 and more efficient with lowered O2, down to a point (eventually if O2 is too low it causes problems due to limited respiration). Growing in a mat may help to reduce the ambient O2 level around many of the cyanobacterial cells and increase the efficiency of N-fixation. This is far from the final word, but may be a significant contributing factor.

Chris

 

[Fredfish]

Interesting. This discussion has pointed out that there is nothing certain around this particular cyanobacteria and the conditions that lead to blooms in our tanks.

It also shows that the macro view is much easier to resolve than the micro view (what is going on with individual species within a bacterial community).

Fred

 

[MCsaxmaster]

And in many respects it is likely the micro view (species-specific interactions) that is determining the macro view, though for a long time this was not appreciated and probably still isn't. Oh, and I'm not sure I would say that there is nothing certain about the growth or blooms of cyanobacteria in marine environments in nature or in our tanks, but that the ecology is more complex than what people often assume.

Chris

 

[mesocosm]

<a href=showthread.php?s=&postid=8526489#post8526489 target=_blank>Originally posted</a> by Fredfish
... Have either of you come across studies or papers postulating what advantage cyanobacteria gains by growing in sheets? ...

The bacterial colonies in natural ecosystems (and presumably in our artificial ecosystems as well) which are large enough to observe directly are typically not monocultures (although sometimes a strain's competitive advantage is so strong that this can develop over time) ... they're assemblages of a variety of strains (oftentimes in direct association with a variety of other classes of microorganisms). In addition to what Chris has already mentioned, I would add that biofilms ("sheets") have the potential to increase biomass, and competitive advantage. For example ...

Most biofilms in their natural environments are likely to consist of consortia of species that influence each other in synergistic and antagonistic manners. ... biofilm biomass was observed to increase by >167% in biofilms formed by the four strains compared to biofilms composed of single strains. When exposed to the antibacterial agent hydrogen peroxide or tetracycline, the relative activity (exposed versus nonexposed biofilms) of the four-species biofilm was markedly higher than that in any of the single-species biofilms. ... In summary, our data strongly indicate that synergistic effects promote biofilm biomass and resistance of the biofilm to antimicrobial agents and bacterial invasion in multispecies biofilms.

Extracted from:
Enhanced Biofilm Formation and Increased Resistance to Antimicrobial Agents and Bacterial Invasion Are Caused by Synergistic Interactions in Multispecies Biofilms
Mette Burmølle, Jeremy S. Webb, Dhana Rao, Lars H. Hansen, Søren J. Sørensen, and Staffan Kjelleberg
Applied and Environmental Microbiology
June, 2006

Abstract Link
http://aem.asm.org/cgi/content/abst...re&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT

:thumbsup: