Question: What is quorum sensing?
Bonnie Bassler: We have been talking about things that are invisible,so bacteria are basically invisible to our eyes and yet we are covered with them, they are on us, they are in us, they are everywhere, and scientists have known about bacteria for almost 400 years, and what bacteria are are these primitive single-celled organisms, the way that they grow is they grow twice their size, their cut themselves down in the middle and then one becomes two. And so for all of these 400 years, everyone has thought that these bacteria are so primitive that they are just out there acting like these asocial organisms. But what we thought about and think about now is that there is no possibility that a bacteria could accomplish all the things they manage and most, like making us sick, lots of terrible things, but also lots of wonderful things, if they were just acting as these little individuals because they couldn’t have an influence on the environment. And so what we have shown and what quorum sensing is is the bacteria make and release tiny little molecules that you can think of like hormones, and so as the cells grow in numbers, these molecules grow on the outside of the cells. And when the molecules hit a certain amount, which is proportional to cell number, the bacteria detect that those molecules are there, so it is a way of counting neighbors, and then all the bacteria change their behavior in unison, and so they start carrying out tasks as enormous groups instead of trying to accomplish these tasks as individuals. So it is just like what we do, you know, if you need to move a piano from here to there, you don’t do it yourself, you wait, you get all your friends, and then you go one, two, three, and everybody does it together. So we call it quorum sensing, so they sort of vote with these chemical votes, they count the votes, and then they say we have enough to do it, and then they do it, whatever it is.
Recorded on: 6/17/08