Quorum Sensing

Many people have never heard of the term, "quorum sensing", which is most likely because it is a relatively new concept. Princeton's Bonnie Bassler and her team of scientists (which consist of her students) have developed a theory of how bacteria communicate with eachother. PBS got an excellent interview with Bassler a few years ago.

 So how exactly does quorum sensing work? Well, as the bacteria grows, it releases a small amount of chemicals called "auto-inducers". The chemical is proportional to the amount of bacteria cells. At first there is just a small amount of the chemical floating around, but after the cells replicate there is more of this chemical. The bacteria can sense with antennae-like sensors on their membrane that there is a significant amount of auto-inducers, and they begin to grab it and take hold. Because of this sensing, they now know that there is enough bacteria cells to do some damage, so to speak. It's basically like the concept that there is "strength in numbers". If just a few little bacteria cells released toxins into the body, it would be very easy for our immune system to identify that there is a toxic foreign substance in our body and fight of the bacteria, but when there is an unfathomable amount of bacteria it is harder for our immune system to fight it off. Your body is covered with bacteria! Your gut alone contains 10¹⁰ bacterial cells. Don't freak out and go stock up on antibiotics--many of the bacteria found in your body are helpful. People used to believe that bacteria cells were asocial, meaning they do not communicate between eachother, for they are unicellulor organisms. They only have one piece of DNA inside of them, making them the simplist for of organism. Bassler questioned the bacteria's actions and the body's response once being attacked: why doesn't the body fight of the bacteria as soon as it releases toxin? It would be much easier to fight off bacteria before it starts asexually reproducing and replicating. After much research, her team discovered that the bacteria chemically communicates with eachother and waits to release toxins until there are roughly 10⁸ or 10⁹ acting against you simultaneously. Smart, huh? It makes it much harder for the body's immune system to fight off such an extravagent amount of bacteria cells, compared to just a few hundred.

There is a certain type of bacteria that is responsible for bioluminescence called Vibrio harveyi.  It produces light due to quorum sensing. Bassler's team discovered that single cells of Vibrio harveyi do not illuminate by themselves. They wait until they have more cells in their colony before they illuminate.

Bassler hopes to some day be able to control quorum sensing and be able to put it into a practical application, such as making insulin from good bacteria and pro-biotics to help us from getting sick in the first place.