We live now in the "Age of Bacteria." Our planet has always been in the "Age of Bacteria," ever since the first fossils—bacteria, of course—were entombed in rocks more than 3 billion years ago.
On any possible, reasonable or fair criterion, bacteria are—and always have been—the dominant forms of life on Earth.
Stephen J. Gould (1996)Bacteria don't get much respect in spite of the fact that many scientists have written about their importance [see Planet of the Bacteria by Stephen Jay Gould (1996)]. Over at Deep Sea News they're trying, once again, to rectify this unfortunate situation. This will be an entire week devoted to microbes [Intro to Microbial Week by Christina Kellogg].
Here are some important facts from the first posting to keep in mind whenever you're inclined to dismiss bacteria.
"The number of prokaryotes [i.e., bacteria + archaea] and the total amount of their cellular carbon on earth are estimated to be 4-6 ×: 1030 cells and 350-550 Pg of C (1 Pg = 1015 g), respectively. Thus the total amount of prokaryotic carbon is 60-100% of the estimated total carbon in plants, and inclusion of prokaryotic carbon in global models will almost double estimates of the amount of carbon stored in living organisms." (Whitman et al. 1998)and
Numerically dominant--there are approximately 1 million bacteria and 10 million viruses in a milliliter of seawater. There are approximately 0.00000000000000000002 sperm whales per milliliter of seawater.The point about learning to love bacteria is that it's crucial to a full understanding of our place in the world of living things. This is going to come up discussions about complexity. We need to understand that our perspective is heavily biased. As Gould (1996) writes,
Our failure to grasp this most evident of biological facts arises in part from the blindness of our arrogance but also, in large measure, as an effect of scale. We are so accustomed to viewing phenomena of our scale—sizes measured in feet and ages in decades—as typical of nature.
Individual bacteria lie beneath our vision and may live no longer than the time I take to eat lunch or my grandfather spent with his evening cigar. But then, who knows? To a bacterium, human bodies might appear as widely dispersed, effectively eternal (or at least geological), massive mountains, fit for all forms of exploitation and fraught with little danger unless a bolus of imported penicillin strikes at some of the nasty brethren.
[Hat Tip: Christopher Taylor at Catalogue of Organisms]
Gould, S.J. (1996) Planet of the Bacteria. Washington Post Horizon 119:(344). An essay adapted from Full House New York: Harmony Books, 1996, pp. 175-192.
10 comments :
> ... there are approximately 1 million bacteria and 10 million viruses in a milliliter of seawater.
And here I thought I was swimming alone.
This reminds me of that frequency graph by Gould plotting population numbers against “complexity”. The graph has an asymptotic tail that thins down to a slither the more ‘complex’ organisms get. I liked it because it was so reminiscent of the Boltzmann distribution: random diffusion pressures lead to energy levels being populated as required by probability (and a given overall energy constraint). In Gould’s graph complexity is agreeably isomorphic with energy: low energy/complexity => high frequencies. High energy/complexity => low frequencies. Life arises because, as with Boltzmann, the probing fingers of diffusion are required by probability to reach the outliers of complexity. Also, like Boltzmann it all swings on the evenhanded play of chance. Nothing is favored, nothing is special. Super Copernicanism.
Trouble is, all this is very likely to be dependent on the bias of the given physical regime; the wrong physical regime and the graph has no asymptotic tail. Moreover, the real wild card is complexity itself: Complex adaptive systems may become so clever that they learn how to transcend Gould’s graph. I suspect that Gould’s graph breaks down completely when some sort of critical mass of intelligence/sentience is reached. The rulebook has to be rewritten once one starts to entertain notions of super-sentience. (And I bet you've guessed what I'm thinking of!)
Bacteria for President 2008!
Here's another big number fact: The human population poops out a *mole* of E. coli in less than a decade.
And E. coli is one of less populous bacteria found in our intestinal tracts.
Well said.
This part of Gould's quote...
"Individual bacteria lie beneath our vision and may live no longer than the time I take to eat lunch or my grandfather spent with his evening cigar."
...reminds me of something I read in a forum once...
"You know, I get the feeling intelligent life is inferior to microbial life. You can find microbes almost anywhere--hundreds of feet below ground, in thermal vents, Apollo space capsules--and here we are, huddled together in a few temperate zones drifting on glorified islands, looking up at the stars with parasite ridden eyes and wondering why nobody else bothered with our way of life.” – Baratos
...not only beneath our vision, but also embedded in our vision.
Me likes.
Shouldn't we go one step further? It seems unfair to measure the success of populations in other terms than biomass. Which is in line with multicellular organisms as glorified examples of cooperating cellular communities. Comparing cell for cell removes the organized and complex characters.
Seems typical human cells weigh ~ 1 ng. With typical sperm whales weighing 25 - 50 Gg (female - male) I get ~ 10^-4 whale cells per milliliter seawater.
Still 10 decades difference (7 if you count the ~ 10* larger diameter of eukaryotes to compare masses), which is impressive. Throwing in the rest of eukaryotes and archaea into the sea won't help much.
As someone noted elsewhere, Bacteria likely outcompeted slower growing Archaea outside extreme environments and Eukarya outside extreme organization. We are truly the scum of the Earth.
Life arises because, as with Boltzmann, the probing fingers of diffusion are required by probability to reach the outliers of complexity.
Much as I like the picture of an asymmetric initial condition (single cell life) and a symmetric process (gaining or loosing complexity), there is a problem with a pure diffusion picture. We observe the distribution to be stably clustered towards simplicity. The simplest is often the best, and that fits here.
Yes, an energy constraint could be the explanation.
Complex adaptive systems may become so clever that they learn how to transcend Gould’s graph. ... The rulebook has to be rewritten once one starts to entertain notions of super-sentience.
Or you could go with the Dyson/Dawkins discussion in Edge, where Dyson likewise proposes that the age of biology could mean the end of an era.
Dawkins answer:
... there really is an interesting sense in which there is an interlude between two periods of horizontal transfer (and we mustn't forget that bacteria still practise horizontal transfer and have done throughout the time when eucaryotes have been in the 'Interlude'). But the interlude in the middle is not the Darwinian Interlude, it is the Meiosis / Sex / Gene-Pool / Species Interlude. ...
If a new period of horizontal transfer is indeed now dawning through technology, genes may become free to compete with other genes more widely yet again.
Yes Torbjorn, the energy constraint makes all the difference with Boltzmann, but let me suggest that the decaying asymptotic tail of Gould's speculative graph would be down to the decaying 'statistical weight' of increasingly large highly organised organisms.
Sorry, lots of frantic hand waving going on here with some rather hairy arguments I realise, but it may have something to do with the new moon. (or should that be full moon?)
Thanks for the Dyson link!
Bedtime here now, better go and get washed and shave (all over) and clean my particularly large cannines.
Timothy Reeves:
Ah, I misunderstood your description.
Well, A Boltzmann distribution needs a temperature to define a partition function to build the distribution of. (That is what the distribution centers around.) That, or a specific energy function description in a continuum approximation.
But we don't have that here AFAIU. So an energy constraint, or a size constraint, could be in effect. (To give your 'statistical weight'.)
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