INTRODUCTION.
Richard Dawkins, in his most famous work, The Selfish Gene, while keeping to an overall system evolution, identify the gene, rather than in species, the main subject of natural selection that leads to the evolutionary process. Dawkins, in fact, states that: "The fundamental unit of selection, selfishness, and then, is neither the species nor group nor in the strict sense of the individual, but the gene, the unit of heredity. "He added, moreover, that scholars and scientists before him have it all wrong because they assumed that the most important developments was the good of the species (or group) rather than the good of the individual (or gene ).
Today, we understand better the nature and especially the behavior of communities of individuals, while not overturning the concept Dawkins, the complement and offset each other in a way quite surprising.
know, in fact, the evolution of social insects (termites, wasps, bees and ants). Here there seems to be a "challenge" to the concept of natural selection, determined by the environment, so individuals with different characteristics have different reproductive success. Social insects show a characteristic that, at first sight, seems incompatible with the vision of Dawkins. In fact, the female bees are prepared to "give up" to play if you develop in normal cells and are exposed to the pheromone of the queen. This feature brings hereditary, in most cases, to zero reproductive success. We know that social insects are descended from solitary species, where each individual develops the ability to reproduce. The development of such behavior reflects a particularly striking case of altruism, that is, behaviors that reduce the reproductive success of those who put them in place for the benefit of relatives. Many naturalists seeking to explain this apparent contradiction, by the reasoning for such waiver to proliferate, to enable a close kin to have many descendants, is a "strategy" winning by natural selection if the amount of an individual to transmit their genes " indirectly "is greater than what is on reproducing itself. In the case of bees, the queen you play a mother or sister of the workers who help, and produces many more descendants of those who could produce a solitary bee.
In one respect, we must also consider the social insects behave as many cells as part of a single organ (the community) and the common good of the community is prefixed to the individual. And in this regard in recent years has come to light a mechanism that could explain in a completely unexpected the source of various social groups of individuals tested by biological evolution. According to Jean Claude Ameisen is the ability to trigger the death of the first time in the biological entities that are organized in society, whether of bacterial colonies, or multicellular animals and social insects. Ameisen's thesis is that apoptosis or programmed cell death, ie death "before time", is the key to explaining the evolution and the individual history of multicellular structures varied and complex, as are the bodies of animals, and certain forms of social organization to be particularly successful, as populations of microorganisms or insect societies. As the cells die by necrosis in the course of inflammatory reactions explode, in apoptosis the cell membrane does not break and there is a sort of collapse and fragmentation directly into the cell. For several decades it was known that cell death during development is used to sculpt the body shape, for example when you have to separate the fingers. In the second half of the eighties has thus demonstrated that cell death is used to select populations of lymphocytes that regulate the immunological control of the self and for structuring the neural networks that incorporate the psychic self. The discovery that this death is programmed and controlled by specific genes and proteins through a mechanism that suppresses the action of specific perpetrators of suicide, normally present in cells, leading to the conclusion that the cells need signals from the social context in which are not to commit suicide. It is then seen that the acquisition of the inability to commit suicide by the cells is one of the crucial steps in the progression of cancer cells to malignancy fatal, but also the onset of autoimmune diseases. By contrast, the cell suicide triggered incorrectly can cause Parkinson's or Alzheimer's.
The genetic selfishness seems so be maximized in the tumor (or tumor) tissue neoplasm composed of atypical cells changed from the normal. The disease is spread by tumor clonality, for lack of cell differentiation and be released from regulatory mechanisms that operate in the body normal.
analyze, therefore, more in dettaglio alcuni comportamenti dei BATTERI:
1) E' noto che la Ps aeruginosa è un batterio cosiddetto "opportunistico", in grado di infettare solo l'ospite con difetto di difese (come in fibrosi cistica, ustioni, AIDS). Per attuare il piano di infezione la Ps aeruginosa produce una enorme quantità di cosiddetti "fattori di virulenza". Molti di questi sono regolati dal sistema "quorum sensing". E' questo un meccanismo per cui un batterio produce delle piccole molecole diffusibili, chiamate AHL, che vengono riconosciute e captate dai batteri circostanti. Quando la concentrazione di queste molecole aumenta oltre una soglia critica, a causa dell'aumento del numero di batteri, i livelli di queste molecole entro le cellule sono sufficienti ad indurre l'attivazione di geni di virulenza, prima silenti, entro il batterio. Tra i fattori generati da questi geni figurano quelli che inducono la formazione di "biofilm", cioè quella sostanza mucoide che protegge gli aggregati batterici (colonie) contro le difese dell'ospite ed anche contro gli antibiotici, in una sorta di resistenza armata. Il "quorum sensing" è dunque un meccanismo di comunicazione tra batteri che li abilita ad agire come comunità nella regolazione di espressione genica. Questo sistema conferisce ai batteri un vantaggio selettivo sulle difese dell'ospite ed è pertanto fondamentale per lo sviluppo della malattia polmonare.
2) Il cannibalismo tra batteri è uno strano comportamento attuato in response to stressors such as malnutrition, the thermal shock conditions and the presence of certain chemicals in the environment. At that point, the colony reduces its population, killing many cells to preserve the other, applying it also seems a rudimentary form of social intelligence that can not destroys the colony. The Israeli researchers at Tel Aviv University, Eshel Ben-Jacob explained, "If we expose the bacterial colonies usually emit chemical signals to avoid competition from other colonies or in response to severe stress, they will do their own work for us killing each other.
3) Discovery of a bacterial protein that controls the size of the colony
Us used to thinking of bacteria as a single-celled organisms, each for himself, however, some findings of recent years have shown that they can communicate with each other as the cells of a multicellular organism. And now it turns out that this comunicazone reached such levels of sophistication to modulate the size of the colonies < sacrificali > inducing suicide. Many bacterial species have a genetic form of suicide, responsible for the production of a dangerous long-lived toxin and antitoxin more unstable (short lived). When the module is on, the synthesis continued dell'antitossina compensates for the presence of the toxin, keeping the bacteria alive. If the form is off, the stocks of antidote and the end batterio muore. Su < Science > un gruppo di ricercatori istraeliani ha chiarito che a controlare questo fenomeno, spegnendo il modulo, è l'azione di una proteina chiamata " fattore di morte extracellulare " ( EDF ), prodotta dai batteri stessi. Ma perchè mai un batterio dovrebbe suicidarsi? La domanda ovviamente non ha senso se lo si considera un organismo unicellulare isolato, ma la prospettiva cambia in un contesto di pluricellularità. del resto non va dimenticato che negli organismi pluricellulari la morte programmata è fondamentale per lo sviluppo. Nei batteri lo scopo è ridurre la densità della colonia in caso di condizioni critiche, come la carenza di nutrienti o la presenza di virus o di antibiotici, che potrebbero debellarla: meglio sacrifice someone and try to resist rather than to die together. < La morte indotta dalla tossina avviene in genere solo in colture sovraffollate. Ora sappiamo perchè: la responsabilità è della proteina EDF >, says the coordinator of the research Engelbergr-Kulka. < In effetti, abbiamo verificato che basta aggiungere questa proteina a una colonia a bassa densità di popolazione per indurre i suoi membri al suicidio >. Even more interesting is the way in which the protein is produced, ie from the degradation of an enzyme. E 'likely that stress induces some bacteria to destroy its enzymes, generating sescreto EDF, which is to communicate to other bacteria to die out if the stress continues. The mechanism is a good candidate for the development of new antibiotics, able to stimulate this form to suicide in bacteria that have it.
4) Self-organization of an amoeba hungry.
Chemotaxis is the phenomenon of micro or macro organisms change their movement pursuant to the merger, or the concentration gradient of a chemical in the environment in which they occur.
AND 'behavior that evolution has largely honored in bacteria, such as basic communication mechanism for the formation of colonies, and for adapting to changing environmental conditions, such as the presence of food or antibiotics. Are many and well documented examples that demonstrate how the interaction with environmental chemicals, which can also be secreted by the bacteria themselves (in this case we speak of chemotactic signaling), leading to the formation of specific patterns surprising, both morphological and behavioral which constitute an effective adaptive response by these microorganisms. Amoeba Dictyostelium discoideum
is that under certain circumstances become a pseudoplasmodio. This microbial taxonomy conceals a matter of considerable interest to those interested in complex systems: if an amoeba is a single-celled organism, a multicellular pseudoplasmodio instead. For this creature chemotaxis plays a recognized role both in the search for food, in which the individual cells "sniff" the concentrations of folic acid to locate food, or in response to a specific environmental stress: lack of nourishment. In this case the cells secrete acrasina and in so doing trigger a process of aggregation, or self-organization, culminating in the formation of a colony of cells.
This aggregate is very consistent, so that it can be distinguished in functional subsystems Members of the motorcycle or sporazione.
What we can observe at one point as a collection of autonomous individuals, in some circumstances engage in unison a series of actions that lead them to join in establishing a single body, without there being a pacemaker cell to direct operations It is the collective response of cells to the spread of acrasina environment to generate the colonial organization.
Today, thirty years after its first draft, the theory of the aggregation of Dictyostelium is recognized as a classic bottom-up studies on the behavior.
Steven Johnson - Emergence.
is not difficult to conclude that the new entity organized collectively emerge from the multitude of individuals. Similarly, if the response of bacteria to the presence of antibiotics, we can say that the collective behavior emerges from a multitude of individual behavior incredibly consistent with the purpose of the action.
communication, or regulation, accompanied by chemotactic life since his appearance probably, and characterizes organisms that inhabit our planet at different scales: from bacteria and amoebae, to multicellular organisms, tissues, neural, social insects, certain behaviors complex animals. Similar mechanisms have been willing to see higher type of social behavior, even up to humans, but this would introduce a universality that evil is not so trivially inferred.
What interests me highlight is the fact that chemotaxis is an example of emergent behavior, where the characteristic of emergency can be clarified as
a property of complex systems:
[A complex system is] a system with multiple agents that interact dynamically in different ways, according to local rules, and indifferent to any high-level education. [...] This system could not really be considered if the emerging local interactions did not produce some kind of macrocomportamento recognizable.
[...] The movement by the rules of low-level to high level of sophistication is what we call emergency. Local
[...] turns out to be the key term to understand the logic of swarm. Observe emergent behavior when individuals turn their attention to a system rather than waiting around for the immediate orders from above, when they think locally and act locally, but their collective action produces global behavior. (Steven Johnson - Emergence.)
5) The micro-organisms like democracy
a complex bacterial community reacts more quickly and efficiently in a stress if the species that comprise it have a uniform distribution of number of individuals.
Bacteria, like humans, live in complex communities characterized by great diversity. And for them to form a "democratic" organization appears to be the most appropriate to ensure the functionality of the entire community. And 'this is the curious conclusion which is a joint study carried out by a consortium of research groups at the University of Milan and the University of Gent, Belgium, coordinated by Daniel Daffonchio.
The research, published early online in Nature, is part of a project on "Microbial Resource Management (MRM Microbial Resource Managenment) which has as its ultimate objective the identification of factors key guiding the behavior of complex microbial communities in various environments, and that, if properly controlled, can afford to take advantage of biotechnology, the microbial communities themselves to applications in agricultural sciences, environmental and biomedical applications.
The concept of biodiversity has a complex joint, which includes aspects taxonomic, functional, spatial and temporal related to the diversity of organisms, with special emphasis on the number of species and their relative abundance. Using experimental microcosms with bacterial communities with the same number of species but with different numbers of individuals for each of them, the study shows that an equal number of individuals for each species initially present in the community is a key factor for the stability and functionality of the ecosystem.
In particular, we show that a community reacts more quickly to a stress if species that make up the show an even distribution of the number of individuals.
If, however, depends heavily on a dominant species, is much more exposed to fluctuations in the environment that surrounds it. In other words, the selection that leads to domination by a few species or the other does not guarantee good performance of the ecosystem.
It is a discovery that opens up interesting prospects for agro-environmental sciences, food sciences and medical microbiology. Molecular techniques have proved successful could be used to predict defects in the functioning of ecosystems and manage biotechnology processes with complex microbial communities, can ensure long-lasting performance. (Gg)
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