Which prokaryotic cells are more abundant on Earth: planktonic (free living) or sessile (adhering to surfaces)? Keep in mind that the ocean waters contain abundant floating surfaces, for example, marine snow.
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This can be calculated from the estimates in:
William B. Whitman, David C. Coleman, and William J. Wiebe
Prokaryotes: The unseen majority
PNAS 1998 95:6578-6583
http://www.pnas.org/content/95/12/6578.full
and the observation that in sediment and subsurface samples, microorganisms are 10-1000 times more abundant in solid samples than groundwater samples (see, for example, this work where the ratio of free-living to planktonic was found to be 1:100):
Lehman, R. Michael, Colwell, Frederick S., Bala, Greg A.
Attached and Unattached Microbial Communities in a Simulated Basalt Aquifer under Fracture- and Porous-Flow Conditions
Appl. Environ. Microbiol. 2001 67: 2799-2809
http://aem.asm.org/cgi/content/full/67/6/2799
Using these estimates, sessile microorganisms (and those in biofilms) far outnumber planktonic organisms. Depending on the values used from the above ranges, there are at between 7 and 50 times as many attached organisms.
Posted by: James H | March 06, 2010 at 04:43 PM