07 April 2010

Nested communities

While my real passion is technology -- the application of science to fight disease and aging, to protect the environment, and to expand the powers of the mind through systems like computers and the internet -- the discoveries of pure science itself often fascinate. Consider the case of Mixotricha paradoxa.

Mixotricha is a protozoan -- a microscopic one-celled organism (there are many species of protozoa, amoebas being another example). Under the microscope, it appears vaguely pear-shaped, covered with about 250,000 "cilia" -- tiny hair-like growths which wave in a synchronized way to propel it through its environment. (That environment itself is of some interest, but I'll get to that in a moment). Many protozoa have cilia, but Mixotricha is different. Its cilia are not really cilia. They are separate organisms, bacteria of the "spirochete" type, long and thin and active. These spirochete bacteria are attached to the surface of the Mixotricha by brackets and are symbiotic with it. They have been compared to rowers propelling a ship.

You might be surprised that 250,000 bacteria could be attached to one protozoan; however, even though bacteria and protozoa are both microscopic one-celled organisms, there is a tremendous difference in size between them.

There exist on Earth two types of cells. The "prokaryotic" type is tiny and simple, without much internal structure; the "eukaryotic" type is far larger, with very complex internal structure including a distinct nucleus. Bacteria, and a class of similar organisms called "archaea", are prokaryotic cells. Protozoa are eukaryotic cells. All multi-cellular organisms -- animals (including our noble selves), plants, fungi, etc. -- are made of eukaryotic cells.

Aside from the spirochetes, three other species of bacteria are symbiotic with Mixotricha, living on or even inside it, performing a variety of functions without which it could not survive, such as extracting energy from the nutrients which it absorbs from its environment.

(It's now believed, by the way, that eukaryotic cells first arose as symbiotic combinations of the original, simpler prokaryotic cells. Modern animal cells contain small fuel-processing bodies called "mitochondria" which have their own DNA and whose "ancestors" must have been bacteria which became symbiotic with larger cells billions of years ago and ended up being absorbed by them. The same is true of the "chloroplasts", photosynthesizing bodies, within plant cells. Mixotricha's symbiotic relationships may resemble the arrangements which gave rise to eukaryotic cells in the first place.)

Mixotricha are not solitary creatures; they swarm through their environment in great numbers. And each individual one of them is, as we have seen, host to a whole community of hundreds of thousands of bacteria.

And what is that environment in which these Mixotricha live? It is the digestive tract of a termite -- specifically, a termite of a species native to northern Australia. You probably know that termites cannot, on their own, digest the cellulose they eat; they depend on micro-organisms inside their digestive systems to do it for them. Mixotricha is one such micro-organism. (Different species of termites use different species of microscopic helpers.)

So each termite contains a huge community of Mixotricha in its gut, without which it could not survive. And each one of those Mixotricha in turn contains a vast number of symbiotic bacteria, without which it, likewise, could not survive.

Nor does it end there. Termites, of course, are social insects, living in colonies of millions. Most of the termites in such a colony are sterile, with the few "queen" termites functioning as egg-laying machines. Rather than viewing each termite as an individual, it's probably more correct to think of an entire colony as a super-organism, with the "queens" being analogous to stem cells which replenish the colony's numbers to replace worker termites as they die off; the flying termites which occasionally leave to start new colonies are the super-organism's reproductive organs, or spores.

Lives within lives within lives within lives.....

13 Comments:

Blogger Tim said...

Infidel
Fascinating stuff. Would you know if Cancer is applicable to all cells.
If only heard Man and animals for now can get it. If these simple cell creatures are immune,I wonder why.
Also I wonder why I think of such stuff.Ha!

07 April, 2010 04:25  
Blogger Infidel753 said...

Tim: Cancer is cells within an organism multiplying out of control, so it only exists in multi-cellular organisms. I think all animals are vulnerable to cancer; I don't know whether plants or fungi can get it (interesting question).

A revolutionary breakthrough in fighting cancer is under way -- see here.

07 April, 2010 04:37  
Blogger Tim said...

Wow I went to that posting. Looks so promising. Yano I know about tiger woods tryst than real news like this.
If it's not salacious, it don't make the news. Thanks for the input.
I love to learn things.
Tim

07 April, 2010 06:17  
Blogger Rita said...

Wow! That blows my mind to think about. I love scientific enlightenment, it's like..."a religious revelation"...Only better :)
Speaking of cancer...my ex greatly benefited from monoclonal antibody treatment for his type of Non-Hodgkin lymphoma. For someone who had periodically gone through chemo therapy treatments over the course of 25 years, this medical advance was like..."a miracle"...only better. :)

07 April, 2010 07:42  
Blogger tnlib said...

There was a reason I flunked practically every science course I took! Can't get too excited about studying termites but I am gald there are people who do. Obviously it serves a very important need. Interesting piece, but have to admit to squirming a bit.

07 April, 2010 08:14  
Blogger Infidel753 said...

Tim: Have no fear -- this blog is guaranteed free of Tiger-Woods-related content.

Rita: Amazing stories are all the more interesting when they're true! Interesting about monoclonal antibodies -- a somewhat similar concept to a vaccine, but I hadn't heard of making antibodies outside the body before.

TNLib: I hate to tell you this, but humans have intestinal micro-organisms too, although I'm not sure what kind or what they do.

07 April, 2010 08:41  
Blogger Ranch Chimp said...

I had to read this a couple time's to absorb, cause it's a lil over my head, but it was an interesting piece indeed. If I'm not mistaken ... in a video I have on Chimp's .... I believe that a segment of it has chimp's that created a sort of tool to like go termite fishing of sort, made from a stick. If so .... I bet those chimp's have one Hell of a digestive system! :)

07 April, 2010 09:35  
Blogger Shaw Kenawe said...

Infidel, I was thinking the same as I read your fascinating post.

We have friendly bacteria in our gut that keeps our digestive tract working. If these friendly parasites get killed off by ingesting too many antibiotics, we "runny" into trouble. ;)

I love to read about the natural sciences.

Right now I'm enjoying Richard Dawkins' newest book "The Greatest Show on Earth, The Evidence for Evolution."

I've also lapped up books by New York Times science writer, Natalie Angier--"The Beauty of the Beastly" was great--it inspired me to write a sonnet about scorpions.

I may even post it here if you ever write about those amazing creatures.

07 April, 2010 10:14  
Blogger Elizabeth said...

Amazing, it really is.

Lives within lives within lives within lives.....

So whose lives are we, human beings, populating, in a microorganism-like fashion?

P.S. No Tiger Woods? No fun. :(

07 April, 2010 11:04  
Blogger Infidel753 said...

RC: Thanks. Yes, chimps do "fish" for termites, using stripped twigs -- this was discovered by Jane Goodall, the first discovered case of a non-human animal actually making a tool, not just using one. And yes, they must have pretty strong stomachs to be able to eat termites (they're actually related to cockroaches).

Shaw: Dawkins is great, isn't he? I've read The Greatest Show on Earth -- and it was in his earlier book The Ancestor's Tale that I first heard about Mixotricha.

Someday I might post about the eurypterids -- the "sea scorpions" of the Ordovician -- they grew up to seven feet long! (Early relatives of that horseshoe crab of yours, I believe.)

Actually the thought of a sonnet about scorpions is rather intriguing -- I hope you'll post it anyway.

Elizabeth: It's fascinating what evolution comes up with. If we are indeed somehow populating the intestines of some higher-order entity, I suspect Tiger Woods is making it rather ill all by himself.

There's a school of thought that treats large human groups like nations as super-organisms, though for myself I don't find it convincing.

07 April, 2010 11:19  
Blogger Shaw Kenawe said...

Okay, I found the poem on my pc.

I think it's appropriate to paste it on a natural science post AND celebrate poetry month at the same time.

(Everything in this sonnet is correct--this is how a scorpion reproduces--also the word "prick" in this poem refers to the the word's second definition, but I do admit there is a double entendre:

2. ": a pointed instrument or weapon b : a sharp projecting organ or part"


SCORPION ENVY

Because he has no prick, a scorpion thrusts
his pedipalps and grasps his gal to coax
her in a cunning promenade-de-deux.
And she, in earnest to perpetuate

her kind, is keen to work with nature’s lack.
With eager stings he urges her to thrill
herself upon a stick he’s oozed with sperm
from his horny absence. She submits,

and sits upon the fertilized imposter
then asks him “Do you come here often?”
Love’s labor on a log in desert sand
secures his progeny, his generation.

He conquered, came, reproduced disphallicly.
His issues met, his race is in the hole.

07 April, 2010 17:14  
Blogger Infidel753 said...

Shaw: How romantic! And clever as well. Thanks!

08 April, 2010 02:44  
Blogger John Myste said...

Jesus!

07 February, 2011 22:56  

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