(On Sacrifice and Common Good)http://shkrobius.livejournal.com/121758.html
(Leaders and followers)...For many pathogens, the outcome of the interaction between host and bacterium is strongly affected by the bacterial population size. Coupling the production of virulence factors with cell population density ensures that the host lacks sufficient time to mount an effective defence against consolidated attack. Such a strategy depends on the ability of an individual bacterial cell to sense other members of the same species and in response, differentially express specific sets of genes. Such cell-cell communication is called "quorum sensing" and involves the activation of a response regulator. http://www.ncbi.nlm.nih.gov/pubmed/11437336?dopt=Abstract&holding=npg
...Bacteria which use quorum sensing produce and secrete signaling compounds called autoinducers. When the inducer binds to it’s receptor, it activates transcription of certain genes, including those for inducer synthesis. When only a few other bacteria of the same kind are in the vicinity, diffusion reduces the concentration of the inducer in the surrounding medium, so the bacteria produce little inducer. With high concentrations of bacteria, the concentration of the inducer passes a threshold, so more inducer is synthesised. This forms a positive feedback loop, and the receptor becomes fully activated. http://microbiologybytes.wordpress.com/2006/09/25/quorum-sensing-in-bacteria-we-two-are-one
...Quorum sensing was first observed in V. fischeri, a bioluminiscent bacterium that lives as a symbiont in the photophore of a squid. When V. fischeri cells are free-living (or planktonic), the autoinducer is at low concentration and thus cells do not luminesce. However, when they are highly concentrated in the photophore transcription of luciferase is induced, leading to bioluminescence. The bioluminescence would not be visible if it were produced by a single cell. By using quorum sensing to limit the production of luciferase to situations when cell populations are large, V. fischeri cells are able to avoid wasting energy on the production of useless products. (Wiki)
The herding mechanism invented by the pathogens for coordinated destruction of their Universe and their immediate gain can also be used to produce light for the sake of the Great Friendly Squid on the High Seas seeking its mate. It's astonishing how little is the difference between people and bacteria...
The bacteria living in the photophore of the squid and cooperatively producing light when there is enough of them have no idea why do they cooperate to produce this light.
When we cooperate, for whom do we cooperate?