Science
Related: About this forumAre Biologists Watching an Evolutionary Leap: One Life Form Absorbing Another?
More than 1.6 billion years ago, one cell engulfed another and put it to work. More specifically, a eukaryotic cell, the sort of cell that contains distinct structures with different functions, took in a blue-green bacterium that could do something it could not: use sunlight to make sugars. The ancient eukaryote then reproduced the bacterium in all of its cells, making it a permanent part of the intracellular environment. What was once an independent microbe was now the chloroplast: the cellular structure, or organelle, that plant cells use to photosynthesize. Theyve been together ever since, an absorption known as endosymbiosis.
Nor, scientists think, were chloroplasts the only parts of cells that were once bacteria: Mitochondria, organelles that produce energy in plant and animal cells, got their start the same way, and some other organelles may have, as well. Now researchers have found another useful bacterium that they think is on its way to becoming a modern organelle of another eukaryotic cellthis time, an alga rather than a plant or animal. Studying this relationship would allow scientists to witness endosymbiosis in action, something they had long theorized but never seen.
The alga and the bacterium met in the ocean, and forged a relationship based on nutrient exchange, researchers report in Science. The alga draws energy from sunlight and produces sugars, which the bacterium uses as fuel. In return, the bacterium processes nitrogen gas into ammonium, which the alga needs. This transfer can occur because the bacterium and the alga live close together, as the scientists know through microscopy and by the fact that the two cell types stayed together during a cell sorting experiment.
In the future, scientists predict, the two will be inseparable; the alga will engulf the bacterium, the bacterium will lose its individual identity and, instead, live as an organelle within the algal cell. The rest will be history.
http://blogs.discovermagazine.com/80beats/2012/09/22/are-biologists-watching-an-evolutionary-leap-one-life-form-absorbing-another/
Xipe Totec
(43,890 posts)Think about it....
aletier_v
(1,773 posts)Speck Tater
(10,618 posts)DetlefK
(16,423 posts)DreamGypsy
(2,252 posts)in general. But there is a very interesting detail!
As Richard Dawkins describes in his book The Ancestor's Tale (2004):
proto-protozoan, entered into a strange relationship with a bacterium: a relationship
similar to that between Mixotricha and its bacteria. As with Mixotricha,
the same thing happened more than once, with different bacteria, the events
possibly separated by hundreds of millions of years. All our cells are like individual
mixotrichs, stuffed with bacteria which have become so transformed by
generations of co-operation with the host cell that their bacterial origins are
almost lost to sight. As with the mixotrich, only more so, the bacteria have
become so intimately enmeshed in the life of the eukaryotic cell that it was a
major scientific triumph to detect that they were there at all.
To understand the connection to the 'mixotrich', Mixotricha paradoxa, you need to read Rendezvous 37 in Dawkin's book. It's a fascinating tale.
The element that is new in the research reported on in the article is that the particular symbiosis described is in the process of occurring from an evolutionary viewpoint. If you traverse the link in the article to New Scientist, the following description is given:
Cool.
exboyfil
(17,865 posts)chloroplast and mitochondria absorption as being characterized as being one off events nearly as unexpected as the initial formation of life. If we are seeing examples in nature of this happening, then maybe it is not such a unique event. Maybe evolution has wiped out other examples over time.
Is important when you consider the possibility of complex life existing elsewhere.
I need to read The Ancestor's Tale. Thanks for the suggestion.
Posteritatis
(18,807 posts)DreamGypsy
(2,252 posts)A retort from the 90 trillion bacteria that account for 90% of the 100 trillion cells in the human body:
such airs. You bipedal apes, you stump-tailed tree-shrews, you desiccated
lobe-fins, you vertebrated worms, you Hoxed-up sponges, you newcomers on the
block, you eukaryotes, you barely distinguishable congregations of a monotonously
narrow parish, you are little more than fancy froth on the surface of bacterial
life. Why, the very cells that build you are themselves colonies of bacteria,
replaying the same old tricks we bacteria discovered a billion years ago. We were
here before you arrived, and we shall be here after you are gone.
Of course, the other 10 trillion 'human' cells are fattened by all that DNA. The bacterial cells weigh only 3 to 5 lbs - a small part of the body weight. But weighed genetically, the microbiome is home to 8 million genes, the human ghetto contributes 22 thousand genes.
Posteritatis
(18,807 posts)Making the illustrations in the paperback version black and white was criminal, dammit.