Talmudic Question #59

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, e.g., marine snow.

Comments

[barry]

Do chloroplasts count?

[James H]

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.

[Shaun Brinsmade]

I would say sessile...not only can one find communities of prokaryotes on "external" surfaces in the environment, but also on the outer and inner surfaces of higher life forms living on earth (i.e., humans and other animals, not to mention other symbiotic relationships). I think I have heard that the common ratio kicked around - microbial cells to cells in a human body - is 10:1.

[John Trawick]

Probably sessile as there must be enormous numbers of prokaryotes in the bottom ooze of the oceans and untold numbers deep within the earth.

[John S. Wilkins]

Reminds me of the debate over allopatry and sympatry, where some sympatric cases (host race isolation) is term "allopatry" because, well, obviously, hosts are different territories...

If it attaches to another cell, is it sessile? If it attaches to a very small structure, a single particle of something? and so on.

[Nathan Myers]

I find I keep repeating "It's no context, obviously it's ...", and alternating between planktonic and sessile.

[Mark O. Martin]

I would think that biofilms on surfaces are the most typical habitat here on Planet Microbe. That isn't to say that there are not some primarily planktonic niches. But we tend not to consider the slippery definition of surface. Such as this:

Michael Cunliffe and J Colin Murrell . (2009). "The sea-surface microlayer is a gelatinous biofilm." The ISME Journal (2009) 3, 1001 – 1003; doi:10.1038/ ismej.2009.69; published online 25 June 2009.

The entire "surface" of the ocean as a vast biofilm? Add that entire electrically conductive nanowires business, and you have Stanislaus Lem's novel, "Solaris."

Although I do wonder about microbes in aerosol droplets of clouds....

[Manuel Sanchez]

My vote goes to sessiles considering those microorganims that are inside the marine sediments.

Planktonic have a hard time dealing with marine viruses according to Danovaro et al 2008

Best Regards

PS: Elio, can I translate and publish in my blog the comment "Mother's Love" by Merry?