Friday, May 23, 2008

some kind of sample

I was reading an interesting article in the NYTimes yesterday about the six different tribes of bacteria that live on the insides of your elbows. It was all information that didn't surprise me, but was interesting to read about. According to the article the type of bacteria that lives there is fairly consistent from person to person. Again interesting but not shocking. I then read that this person's sample size was five people. (If I misunderstood the article the rest of this post is completely worthless).

Five people? Your sample size was only five people. Surely you know more than five people who wouldn't mind having a swab of their inner elbow taken. Wouldn't you want more samples before stating something about the consistency of the type of bacteria tribes from person to person?

wouldn't you want to know if someone half way around the globe has the same bacteria growing on them? I think that would be interesting to find out. All of this isn't that hard.

Anyhow this discovery is part of a larger project to find out what bacteria live in the human ecosystem, which is very cool.


Elizabeth said...

So, yes, you do want to test more than five people. But they're not just running a gram staining test on these cultures; they're doing full genome sequences of six organisms each time. Even with fancy modern high through-put sequencing techniques, culturing, purifying, and sequencing 30 genomes is still a bit of work, and thoroughly analyzing all of that data (which is really what NHGRI specializes in at this point) is mammoth.

Also, a sample size of five people is large enough to establish or, rather, hint at whether elbow bacteria vary as widely as gut bacteria -- as was mentioned later in the article, everyone has a unique set of gut bacteria; except identical twins.

Having not read the original paper, I can't say more than that? But my hunch is that you're overreacting to what is probably a minor issue.

Embly said...

I hadn't thought about the fact that they were not merely making cultures but were rather sequencing the genomes.

I figured that there was a good reason for the sample size otherwise they would not have mentioned in the New York Times that they sample size was only 5 people.

My reaction was also really strange insofar as I was confused by the fact that there were only 5 samples, yet that did not make me believe the findings any less.

Also, I love how diverse gut fauna is!