Dictyostelium discoideum is an amoeba, a unicellular organism that moves in the decaying leaves them with organic, typically in the litter of dead leaves, humus, etc.., where it feeds the bacteria that thrive there. At the time of my textbook of Botany, of ... nt'anni ago, was still classified in quell'eterogeneo and fascinating group of non-mushroom fungus were the myxomycetes, I see that most modern taxonomies exclude any relationship with mushrooms and place it among the protists, while maintaining a vague reference in the name of the Phylum Micetozoi.
The peculiarity of these organisms is the ability, when food or moisture starts to run low, to bring together tens of thousands of individual cells, which fuse together to form a pseudoplasmodio, that is a giant cellulone single, a few millimeters, with tens of thousands of nuclei. The pseudoplasmodio roughly takes the form of a snail crawling and migrate in search of more favorable environments, covering tens of centimeters. Found a niche, there is setting up to form a fruiting body with a stem and a bulb (sporangia) containing the spores to be released in the new environment, where individual cells back to being separate and independent entities.
is an organism well known and studied in many laboratories around the world, so that now the biochemical mechanisms that govern the aggregation of cells are quite well known.
But a few days ago an article published in the journal Nature (1) reveals an hitherto unknown, and our rather impressive Dictyostelium : Some clones of these amoebae have the ability to bring behind their favorite bacteria during migration, then sow them to the new location.
In practice, the cell line "farmers" stop eating a little before "non-farmers" and, before starting the migration, "the bags are" incorporating live bacteria which are then stored in appearing reproductive and released together with spores in the new habitat.
This is an obvious advantage if the place where you develop the fruiting body lacks the bacterial flora, or that this is not particularly edible: the amoeba seed, literally, to feed upon the bacteria to grow around them itself.
strains "non-farmers", on the other hand, have the advantage of eating more and accumulate greater amounts of energy, and it was noted that as long as they can find situations of abundance, they reproduce more efficiently strains "breeders."
addition, "farmers" migrate, on average, for shorter distances, but it is said that this is a negative backlash due to the lower energy: maybe it is instead a positive effect on their ability to create for itself a more favorable environment , and then they need to do, on average, less road to find a suitable place.
We humans have learned to play and raise our food sources, rather than just hunt them down, not before 10-11000 years ago, we were preceded by a few tens of millions of years from ants and termites, actively raising fungi and aphids, and now we find that this ability is present even in very simple organisms (and does a little impression noted that the invention of agriculture led to the man abandoned the nomadic life, and that even amoebas become more "sedentary" if they are able to sow their food).
But another aspect of this discovery has given me a bit to think about: how a micro-organism so well known, bred in the laboratory for a long time and the subject of studies around the world, today revealed only a feature that interesting? Brock and colleagues collected 35 wild clones of Dictyostelium, and found that about one third of them are "breeders of bacteria, a property which seems determined genetically. Laboratories around the world, for decades they exchanged their isolated, in search of the most favorable for its work in vitro, and the result is that virtually everyone uses the same strain, isolated in the '30s; just happened that this is a "non-breeder."
are problems that happen when you do not consider variability as an intrinsic and essential species (and a bit of all our categories, however, identify them), but a sort of accident of disturbance. In this case were the contingencies of practical use to drive our knowledge towards a model uniformitaristico, and however the result was losing the essence of what he was observing. But in general it is still difficult to separate from the Platonic heritage that still invite us to consider the "ideal type" as a distinguishing feature of the categories through which we order our world view, and the change as an annoying flaw.
We should learn to always consider the variability as a constituent of its own, distinctive, and positive irriducible of our classificatory categories: in a kind of evolution is diversity, not the approval, the measure of excellence.
(1) Debra A. Brock, Tracy E. Douglas, David C. Queller & Joan E. Strassmann
Primitive agriculture in a social amoeba
Nature, Vol: 469 (2011), Pages: 393-396.
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