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Monday, January 10, 2011

Bacteria and the Human Body

Thanks to Regan:

The video opens up with an interesting point: On and inside of the human body there are 10 times as many bacterial cells as there are human cells. Not only that but these bacterial cells constitute 100 times as many genes as there are in the human genome. Essentially our biological systems are 90 to 99% bacterial, depending on how you look at it. The idea that bacteria can exist in this symbiotic relationship with humans to such a great extent makes you realize just how complicated biological systems can be. This idea really hits home when you look at how complicated something even as small and primitive as bacteria can be. Bassler shows an incredible example of the complexity of bacteria as well as symbiotic relationships with Vibrio fischeri. This bioluminescent bacteria exists on the the body of the Hawaiian Bobtail Squid and is actually used to hide the squid's shadow by producing enough light to counteract the light shining down on squid's back! With the help of Vibrio fischeri, this squid is the stealth bomber of the sea as Bassler puts it.

Almost as cool is how the bacteria work. The Vibrio fischeri only turn on when there is a large amount of it existing together, and when it does turn on, all the bacteria cells turn on at the same time. This is because the Vibrio fischeri, as well as all other bacteria, secrete molecules that can be detected by nearby bacteria cells. When the bacteria detects enough of these molecules it will light up. This idea is exactly the same in harmful bacteria that invade human bodies. The bacteria enter the body, replicate, and then when they recognize there is enough bacteria to take on their host they become virulent and all attack at once.
The most interesting part of all of this is how this knowledge can be applied. Most bacterial infections today are fought with antibiotics that work to kill the infectious bacteria by some mechanism such as destroying the bacterial membrane or halting the bacterias' ability to replicate. The major problem with this strategy is that the antibiotics don't kill all of the bacteria and can give mutant, more drug resistant bacteria less competition by killing off all the weaker bacteria. Eventually it could come to a point where our antibiotics are hardly effective for treating bacterial infections. What Bassler is proposing would be not to kill the bacteria, but to block their communication. Her lab discovered that the molecules that bacteria secrete bind to proteins in other bacteria cell membranes allowing them to communicate. They also developed a method for disabling this communication by introducing a molecule that binds to these receptor proteins and blocks the other molecules. Could this method be the future to making safer, more effective antibiotics? I think it is something that is definitely worth looking into.


  1. she missed the big point...animals/human have other properties to control bacteria growth. Just as how squid learn to control bacteria we forgotten these controls.