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Biotech Science

Bacterial Prisoner's Dilemma and Game Theory 95

Posted by Soulskill
from the sporulate-is-the-word-of-the-day dept.
dumuzi writes "Scientists studying how bacteria under stress collectively weigh and initiate different survival strategies say they have gained new insights into how humans make strategic decisions that affect their health, wealth and the fate of others in society. The authors of the new study are theoretical physicists and chemists at the University of California, San Diego's Center for Theoretical Biological Physics. In nature, bacteria live in large colonies whose numbers may reach up to 100 times the number of people on earth. Many bacteria respond to extreme stress — such as starvation, poisoning and irradiation — by creating spores. Alternately the bacteria may 'choose' to enter a state called competence where they are able to absorb the nutrients from their newly deceased comrades. 'Each bacterium in the colony communicates via chemical messages and performs a sophisticated decision making process using a specialized network of genes and proteins. Modeling this complex interplay of genes and proteins by the bacteria enabled the scientists to assess the pros and cons of different choices in game theory. It pays for the individual cell to take the risk and escape into competence only if it notices that the majority of the cells decide to sporulate,' explained Onuchic. 'But if this is the case, it should not take this chance because most of the other cells might reach the same conclusion and escape from sporulation.'"
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Bacterial Prisoner's Dilemma and Game Theory

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  • by v1 (525388) on Sunday December 13, 2009 @02:53PM (#30424076) Homepage Journal

    a case of where the individuals are all trying to make decisions that are selfish, but if everyone is selfish, no one wins, so some have to be selfish and some have to fold, for any to survive. I seem to remember playing games like that as a kid, where it was basically a game of chicken, where no one could do anything until everyone was generous, and so everyone then starts building up, and whoever managed to switch back to greedy first won. Also reminiscent of the stock market during a bubble, eh?

  • Re:Thinking Bacteria (Score:5, Interesting)

    by fuzzyfuzzyfungus (1223518) on Sunday December 13, 2009 @03:25PM (#30424284) Journal
    Obviously the bacteria aren't "thinking" in any way that could usefully be crammed into the usual definition of the word; but I don't think that either "sophisticated" or "decision" are being distorted at all.

    It is quite common, for instance, to refer machines that have a fair number of parts and are good at what they do as "sophisticated"("a sophisticated inertial navigation mechanism"). Even unicellular procaryotes have a fair amount going on inside, so they could easily fall under this definition.

    As for "decision", that certainly can imply a process of rational, reflective cogitation; but it is also quite commonly applied to fairly simple, entirely mechanistic, things. "Decision Algorithms", for instance, are explicitly designed to be mechanistic and, as their name suggests, make decisions. The idea that the process whereby a cell enters either stateA or stateB depending on certain inputs is a "decision process" seems wholly reasonable to me.
  • by TubeSteak (669689) on Sunday December 13, 2009 @03:45PM (#30424444) Journal

    I seem to remember playing games like that as a kid, where it was basically a game of chicken, where no one could do anything until everyone was generous, and so everyone then starts building up, and whoever managed to switch back to greedy first won. Also reminiscent of the stock market during a bubble, eh?

    Stock markets do not allow for equal access to information.
    That inequality seriously skews any game theory in favor of the well connected.

  • by linhares (1241614) on Sunday December 13, 2009 @04:04PM (#30424576)
    human population growth is much more bacteria-like than primate-like.
  • by JoshuaZ (1134087) on Sunday December 13, 2009 @04:08PM (#30424602) Homepage
    Conway's Game of Life wasn't made to simulate life in any meaningful sense. It was designed by Conway because he was investigating simple cellular automata that had non-trivial behavior. http://en.wikipedia.org/wiki/Conway's_Game_of_Life [wikipedia.org]. It happened that the simplest interesting form he found happened to have rules that could be stated with very very rough analogs to living creatures. Some of the rules are very much stretches. For example, while bacteria can die from overcrowding, they cannot die from being lonely. And cells aren't reincarnated or made new from having three neighboring cells (I'm not aware of any species outside science fiction that requires more than two cooperating members to have sex (see for example Asimov's "The Gods Themselves")).
  • Re:Thinking Bacteria (Score:3, Interesting)

    by hazem (472289) on Sunday December 13, 2009 @05:23PM (#30425204) Journal

    One might just as well argue that water flowing down hill has made a sophisticated decision.

    Actually, the behaviors and communication of groups of bacteria are much more complex than water flowing downhill. Consider that when you get a bacterial infection, the bacteria will typically work in a "growth phase" where they are multiplying but not doing being virulent. When the bacteria reach a certain population size (or density), they all switch on their virulence. Individuals are making decisions that actually manifest as a group decision. Water molecules do not do this.

    A very interesting lecture on this is at:
    http://www.ted.com/talks/bonnie_bassler_on_how_bacteria_communicate.html [ted.com]

  • by Cassius Corodes (1084513) on Sunday December 13, 2009 @09:12PM (#30426764)
    They are - and for good reason. Game theory has been very successful in understanding some of the basic trade-offs involved in individual vs group decision-making. Certain set-ups such as the http://en.wikipedia.org/wiki/Prisoners_dilemma [wikipedia.org] are generic forms of common problems that are encountered both in the human world and the natural world. Having worked in this area I can tell you that solutions found in the natural world often end up as inspiration for real life applications - such as regulation of industry and organisational psychology. At the end of the day one of the most re-occurring problems is how to get selfish people to co-operate as a group - and this problem has been solved so many times by nature in so many ways its basically a handy repository of tried and true solutions just waiting to be discovered.
  • Re:Thinking Bacteria (Score:3, Interesting)

    by TapeCutter (624760) * on Sunday December 13, 2009 @09:48PM (#30427050) Journal
    Please explain how the chemical process in your head do not lead to your decision that there is no decision.
  • Re:Thinking Bacteria (Score:3, Interesting)

    by Cassius Corodes (1084513) on Sunday December 13, 2009 @10:11PM (#30427222)
    Why do you need intelligence to do decision-making? This seems an arbitrary requirement - and the literature on decision-making doesn't use intelligence as a prerequisite, rather it refers to cognition - which is more rigorously defined and can be automated.

    Your example of grass and dogs seems quite confused - grass lacks the ability to move in real time so the notion of it being unable to choose to lay down seems bizarre, unless I am missing something. According to this one could argue that a failure of a dog to teleport out of the way of a bus shows their inability to make decisions! Likewise chemicals are following externally set rules in physics, there is no internal selection of outcome.

    Perhaps the difference in our thinking relies on the definition of decision-making. The one I use is the one used in most decision-making literature, which roughly states is "a cognitive process of selecting among several different options based on external and internal factors." According to this the bacteria is engaging in decision making as it is selecting for several different courses of action. Its use of cognition is pretty basic, but more that enough to satisfy that criteria - its processing information and applying internal biases to select a course of action.

    Also your statement about bacteria being sacks of chemicals and micro structures and its reaction is just as applicable to humans and dogs as to bacteria. Remember that we are made up of individual cells too.

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