Autopoieis and the Logic of Cellular Life

Cell's life is the starting point for the development ofautopoiesis (from Greek auto = self, poiesis = production), introduced in the Seventies by the two Chilean biologists Humberto R. Maturana and Francisco J. Varela.2,3,7 Autopoiesis does not concern the origins of life, but answers instead to the question "what is life ?", analyzing the living organism as it is here and now. In this sense, autopoiesis is a descriptive theory based on phenomenology and starts from the recognition that the main activity of the cell is the maintenance of its own individuality: this is so despite the large number of transformations taking place inside its boundary. This is possible thanks to the fact that the cell regenerates from the inside all components that are being transformed away (boundary molecules included!). Thus, very simply, the blue print for the life of a cell resides in a series of processes that produce all the cell's components that in turn produce the processes that produce such components. This occurs of course at the expense of energy and nutrients from the outside, so that the living cell is thermo dynamically speaking an open system, yet characterized by its own operational closure, i.e., it contains all the information to organize and reproduce itselffrom inside the boundary.

This is actually all very simple. Autopoiesis recognizes in the working of the living cell the complementarity between two levels: organization and structure. Organization is the invariant property ofall living cells and is based on the production ofcomponents that self-organize into an organized reaction network of processes that makes the components and thus perpetuates a circular logic (Fig. 12.2). In contrast, the structure may vary from cell to cell and also in the course of the evolution of a cell.

Several importantconcepts are associated with this cellular view, such as biological autonomy, social autopoiesis, second order an-topoiesis and third order autopoiesis (depending on the complexity ofthe living organism), etc. The reader is referred to an introduction to autopoiesis in Luisi, 20 062), which also contains information about the historical background and considerations on why the autopoiesis theory has not generated a large impact on contemporary biochemistry. Here it may be mentioned that in order to have a complete picture ofthe living state, the notion autopoiesis needs to be complemented by that ofcognition, also developed by Maturana and Varela7—namely the selective interaction with the environment.8,9

Autopoiesis is closely connected with the definition of life at the cellular level. In fact, the property of being alive belongs to the cell as a whole and not to its individual parts. In this regard, autopoiesis is related to the compartment approach described in the Introduction, not because it explains how compartments are generated, but because it emphasizes that investigations on the origin of living entities must be focused on compartmentalized systems and not on single molecules.

In the following paragraphs, when the self-reproduction of compartments will be discussed, it will be shown how autopoiesis inspired these studies and how a simple autopoietic chemical system was realized in the laboratory.

Figure 12.2. The cyclic logic of cellular life. The cell, being an au-topoietic unit, is a self-organized bounded system that determines a network of reactions, which in turn produces molecular components that assemble into the organized system, that determines the reactions network, that...
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