[thedoc (OP)]

Stan asked the Naked Scientists:
     
Dear Sirs,

I am a long time listener to the naked scientist.

A statistic that is often quoted is that only 10% of the cells in our body are us.

http://discovermagazine.com/2007/jun/your-body-is-a-planet

This does seem counter intuitive. I wondered if you would look behind these numbers. I assume we are talking % of total cell numbers, not 90% of the mass of cells. Or could be take anti-biotics and lose 90% of our weight!?

I am aware that certain lab animals are born "sterile" delivered by caesarian section, again what is the comparable mass of a sterile animal/human?

I hope you will find some fascinating insight behind these numbers.

regards, Stan
Brisbane,
Australia
   
What do you think?

[CliffordK]

I've seen the estimates. 
Does it count before, or after sitting on the can?

Keep in mind that most prokaryotes are much smaller than eukaryotes. 
Obviously there is a range in sizes, but I'm seeing notes of:

Bacteria are typically 0.2-2.0 μm in diameter
Eukaryote cells are typically 10-100 μm in diameter

So, if one dimension is 10 to 100 times as much, the cube of that gives a volume of the eukaryotes 1,000 to 1,000,000 that of the prokaryotes.  So, the actual weight attributable to the prokaryotes and other flora is actually quite small.