Infection and Immunity, August 2002, p. 4099-4105, Vol. 70, No. 8

LuxS-Mediated Quorum Sensing in Borrelia burgdorferi, the Lyme Disease Spirochete

Brian Stevenson and Kelly Babb

This title is essentially the answer to the question the paper asks.
So what are Borrelia, and what is Quorum Sensing?

Borrelia, as the article's title proclaims, are the organisms which cause Lyme disease. They do a whole little life-cycle dance involving ticks and mammal hosts, playing with animal cells, immune systems and, apprently, each other.

Quorum sensing is the name, apt or not, given to a host of feedback systems in which a constantly secreted small molecule is simultaneously detected by the same cell. This could serve to detect a number of things. One hypothesis is that it serves to detect how much room for diffusion is present in the immediate neighborhood. Another is that is serves to detect other organisms producing the same chemical. This second hypothesis is the "quorum" part. Are there enough of "us" to do something?

Anyway, the typical systems involved have been divided by the type of small molecule produced. In this case, LuxS is an enzyme involved in a pathway involving 'AI-2' (autoinducer-2, because the molecule induces activity from the same cell that produces it).

The trick for the authors was demonstrating that the cells had a valid LuxS to help produce AI-2, a response to AI-2, and actual production of AI-2. They had trouble with step three, but they got some very neat, temperature dependent repsonses to AI-2, as well as an active LuxS.

Temperature dependence in the responses to AI-2 hints at the possibility of host context dependence for the AI-2 pathway. Very cool stuff.

So what are these dasterdly organisms scheming and plotting together?... that will probably be found in a later installment, where they analyze the genes that are activated.

Good work!