Imagine a group of cowherds in a village letting their animals graze on a common meadow. Each is entitled to, say, six cows to graze. If now a farmer brings an extra animal or two to graze there, and does not help in maintaining the grassland, he free-loads or cheats. If this goes on uncontrolled, soon the meadow will dry up. The cheater or freeloader ruins the public good for the sake of private good. This is the tragedy of the commons.
How does one avert tragedy? Dr Garrett Hardin, who popularised this phrase through his paper in Science in 1968, was referring to issues such as overpopulation or environmental degradation, and suggested that it may be done by government regulation, or by privatising the “public good.”
Does this not ring a worrisome bell? When the Chinese government came out with their single–child law, it was (and is) very unpopular, and has led to familial and community problems. When resources (say land, mines, coal, natural gas, etc) are privatised, the invariable results are corruption, cronyism and overuse of non-renewable resources. We see these rampant in current day India, where we witness a tragedy of the commons. And the Hardin solution is hardly a solution!
How then does one avert the tragedy of the commons? Well nature, specifically biology, has been offering a solution even before we humans came on earth. Bacteria have found a solution. A beautiful example of this has just been published by Drs. Ajay Dandekar, Sudha Chugani and Peter Greenberg in the 12 October 2012 issue of Science, on the bacterium known as Pseudomonas aeruginosa. This grows in colonies, where individuals communicate between themselves. This cell-cell communication is termed “quorum sensing” (an anthropo-centric term, if ever was one). They use such sensing in order to generate and control the production of public goods. The example of such a public good cited by the authors is the production of an enzyme that breaks down the available food material, say milk protein, into easier absorbable material so that all may use it for food and grow. A single individual does not make this enzyme. A quorum is needed to produce this public good, and the quorum is gathered through inter-cell signalling using specific molecules which turn on the enzyme-producing genes.
Now imagine a mutant in the colony which is not able to respond to such quorum signalling and sensing. Hence it does not participate in making or contributing to the public good — the extra-cellular enzyme, yet it can free-load for personal benefit. It is thus a cheater, and can in time generate more and more of itself, overtaking the population by breeding more, leading eventually to a tragedy of the commons.
The Greenberg trio found that the bacterium has a built-in control mechanism. Just as the quorum produces the food-processing enzyme for common food, it is also able to produce another enzyme for metabolism of the compound adenosine, which goes to arrest the growth of ‘cheaters’ or mutants. When the group cultured P. aeruginosa in a medium containing the milk protein casein as the food source, quorum sensing was found to occur through the signal molecules that they dubbed as C12-HSL and LasR. These signals activated each cell to help produce the enzyme to digest the ‘common good’ casein, which is then used as food by the cells.
But it also led to the emergence of ‘cheaters’ mutant cells that do not help in making the enzyme. If their numbers are not controlled, they can overrun the colony and cause havoc. It is here that the authors found the bacterium to have a remarkable correction mechanism. The same quorum sensor molecule LasR regulates the production of the enzyme which can handle adenosine in the normal (or wild type) cells but stop such ability in the mutant. This mechanism allows the co-operators to grow and the cheaters to decline. Here then is a self-correcting mechanism by the colony itself whereby the good guys grow and the cheaters controlled.
No outside intervention
Notice that there is no external intervention; no extra-community (say government) control. Indeed, several scholars have suggested that such external mechanisms do not work well. Notable among them is the Late Professor Elinor Ostrom, the only lady so far to have won the Nobel Prize in Economics (she received it in 2009). She showed through a variety of examples that control by the user community of common good works better than external intervention. The Nobel citation of her work states: “Elinor Ostrom has challenged the conventional wisdom that common property is poorly managed and should be either regulated by central authorities or privatized. Based on numerous studies of user-managed fish stocks, pastures, woods, lakes, and groundwater basins, Ostrom concludes that the outcomes are, more often than not, better than predicted by standard theories. She observes that resource users frequently develop sophisticated mechanisms for decision-making and rule enforcement to handle conflicts of interest, and she characterises the rules that promote successful outcomes.”
Sadly, Professor Ostrom passed away on June 12 this year of pancreatic cancer, and the Dandekar, Chugani, Greenberg paper came out 4 months later. She would have been delighted to know that bacteria know what she wrote in her book “Rules, Games and Common Pool Resources” (University of Michigan Press, 1994; downloadable free.