Greenberg and his collaborators have recently shown that P. aeruginosa strains with defective quorum sensing systems form abnormally thin films that succumb to detergents, he says. Scientists have found that particular compounds in the environment stimulate quorum sensing. Agrobacterium tumefaciens, an organism that causes tumors in plants, directs its host to make certain substances. In addition to providing nutrition for the bacterium, the host chemicals spur A. tumefaciens to produce a responsive protein. This, in turn, enables individual bacteria to detect the presence of their neighbors.
Scientists say other bacteria probably use a similar scheme for figuring out where they are.
This tactic ensures that they invest in the equipment with which to sense population density only under specific conditions. F or the most part, scientists have focused on the detailed mechanics of quorum sensing. Only recently have they begun to move their studies from the laboratory into the field. Pierson studies Pseudomonas aureofaciens, a bacterium that infects and benefits wheat plants. In large numbers, it makes an antibiotic that inhibits the growth of a fungus that causes take-all disease, which can ruin entire wheat harvests.