Quorum Sensing - How Bacteria Keep You Alive

Periodically I talk about nutrition-related issues here.

Recently I watched a video by Bonnie Bassler on TED.  Bassler is a microbiologist from Princeton University.

Bassler's area of study is how do bacteria communicate.  In particular her group has discovered that bacteria speak to other bacteria of the same species in a species-orient molecular language and that bacteria speak to other bacteria in a more general molecular oriented language.

You can watch the TED talk but to summarize it works like this.
A particular bacterial species will emit a chemical compound.  At the same time that its emitting the compound its also "listening" for that compound.  The bacteria "listen" until the volume of that compound exceeds a certain threshold at which point the bacteria takes some species-specific action.

This is called "quorum sensing." The molecular "signals" are called "autoinducers."


You can think of this as follows:  You are standing in a large swimming pool with a bottle of red food coloring.  Periodically you put a drop into the pool.

When there's just you the coloring is immediate diluted away and broken down.

But now add more people doing the same thing.  Eventually the pool will start to show a tinge of red.

This is how the bacteria operate according to Bassler.  The live effectively solitary lives dropping their little bits of color into the pool.  Only when they detect a change in the "water" do they act.

So for a bacterial disease that emits a toxin the infection does not start off with a tiny number of bacteria emitting the toxin and that number of bacteria multiplying.  Instead the bacteria multiply without emitting the toxin.  As they multiply they "test" for the appropriate marker (not the toxin) and when there are enough bacteria to trigger a response from the host they all respond at once.

Bassler found some of these signals are specific to a bacterial species and others work across species.

So what does this have to do with nutrition you might ask?

Well, for one thing our digestive tracts contain perhaps 5-10 pounds of bacteria.  No one knows how many species are typical for humans but a safe estimate is around 500 unique species with perhaps 30 to 50 making up the bulk of the bacteria.

These bacteria perform an amazing range of functions from digestion of certain types of food to repressing certain types of infections to supporting immunity to preventing allergies.

Without your symbiotic bacteria in your digestive system (at least) you cannot live.

To me Bassler's work says that not only are these bacteria performing these functions within our bodies but that they are also A) working together - both within and out side of their species and B) if they are emitting chemicals to communicate our bodies are probably receptive to these same "auotinducers" as well.

So my thoughts are:

1) The "gene pool" of all of these bacterial species in our bodies far exceeds the size and complexity of our own human genome.

2) These bacteria are symbiotic with our human bodies (as well as most other living creatures as well I would imagine).

3) All of these bacteria are communicating constantly between themselves and with us.

I think that #3 is the most important and interesting.

Many bacteria communicate with lactone-based compounds (see Bassler's talk) - in particular γ-butyrolactone (the five-sided version below).  These are cyclic esters related to alcohol and carboxylic acid.  They occur, for example, in oak trees and provide flavor to whiskey.

So clearly they can and do react with our bodies - if we can taste whiskey then we can probably sense lactones.

This all tells me that within our bodies there is a complex interaction between all of these bacteria and our selves.  This interaction is carried on with constant communication via chemical signals.  There are many pounds and literally trillions of cells - both in our bodies and in our bacterial symbiotic partners.

Now let's take a look at what modern medicine does with this information...

Nothing.

Bassler goes so far as to suggest using techniques to disrupt this communication as alternatives for antibiotics.

But what would that mean?

Well human brain's contain maybe 100 billion neurons.  But our bodies and their corresponding bacteria contain ten or hundred times more cells.

Its seems hard to imagine that simply stomping all over the basic communication in a system this complex is really going to provide anything beneficial in the long run.

These number suggest that our bodies and their symbiotic partners the bacteria make up a complex, communicating system at least as complicated as a brain.

In fact, I think its very likely that via your body your brain has an indirect sense of what's going on at some level with a lot of this symbiotic activity - how can it not when you think about it?

So modern medicine's approach to all this is today to kill off bacteria indiscriminately with antibiotics.  (I have covered this in detail in other posts such as "Antibiotics = Childhood Asthma").

What do you suppose this does to the over all digestive health of the organism?

After some consideration I think this is like treating mental illness by drilling hole through someone's brain.

While a treatment like this may cause some positive outcomes for treating certain symptoms I cannot see their long term benefit.

No, I think that modern medical science (at least the part that's related to "treating" human disease) has missed the mark by a wide margin.

If you consider the overall complexity and what our treatments like antibiotics do we're basically in the stone age treating mental illness with trepination (drilling holes in the head).

Science needs to move forward and find a way to deal with and understand large complex systems - whether a brain or a human body.

Without this we are all going to suffer from treatments that are ultimately worse than the disease.

When you think about all the "digestive-related" problems (from obesity to asthma to bowel problems) that people in the US suffer I think that a huge percentage of them can be tied to either A) bad nutrition or B) bad treatments.

You have to ask what do all the chemicals, hormones, genetically modified cells, artificial oils and all the rest do to this communication system?

What happens when you indiscriminately kill off a whole section of bacteria that serve some useful purpose in the human body?

What happens when you prevent children from building up a properly configured symbiotic bacterial system in their bodies by using too much "hand sanitizer" and preventing them from eating dirt?

No one is asking these questions... No one.

Yet we are all victims of this process.

Certainly medical knowledge has dramatically advanced because we can understand that some of these things are going - and I have no argument with that.

The problem is what we do with that knowledge: we create dangerous foods, treatments, and so on that do far more harm than good.

And we foist them all off on an unknowing public.