[Aaron Stephens]

Aaron Stephens  asked the Naked Scientists:
   
Hello Chris,

I would say I'm a big fan but at 5'4" that wouldn't be terribly accurate. Ha! Anyway I was wondering if any progress had been made in the development of an iPhone/iPad app? Currently  I have to use cloudbrowse when I want to view the kitchen science videos on my iPad, one of my favorite parts of the show.

On a separate note could you please help me sort out something with respect to the bacterial biota that are a part of us? I've heard several times that we are more bacteria than we are ourselves.  Is this simply in number of cells or is this in biomass? I would not be surprised if there were a greater number of bacteria cells in and on us than there are actual cells with our DNA, but I would be very surprised if more of our biomass came from bacterial cells than our own cells. So which is it?

Thanks,

Aaron

What do you think?

[Phil1907]

Interesting question.  You're probably right - folks estmate the weight of an "average" bacterial cell is about 10E-13 g vs. about 10E-9 for an "average" human cell.  Even if we were 99% microbial in composition, these four orders of magnitude would leave us weighted as human.

[Dimz]

It is true that there are more actual bacterial cells in our gut, then there are in our entire body, by quite a vast amount. I was told it many times in my lectures regarding xenobiotics, we need such a vast amount to break down foods that we cannot normally digest.

With regards to the biomass, I am not sure about this one. You have to appreciate that a large percentage of our body weight is most likely from water that isn't associated with our body cells, but is extra-cellular. Our body mass doesn't just come from our cells alone, so it could well be possible that the ratio between the weight of bacterial and self cells is higher with regards to bacterial cells!

[chris]

The bug burden in the bowel (lovely alliteration there) is about 100 trillion cells. They weigh a kilo or so. We're therefore outnumbered at least fifty to one in cellular terms by these passengers, but as they are considerably smaller than our own cells, we're still weightier than they are are.

The mind boggles at the thought of what would happen if things were the other way around...