Friday, June 02, 2006

Biologist Says We're Not All Human

Excerpted from a story on
We may not be entirely human, gene experts said on Thursday after studying the DNA of hundreds of different kinds of bacteria in the human gut.

Bacteria are so important to key functions such as digestion and the immune system that we may be truly symbiotic organisms - relying on one another for life itself, the scientists write in Friday’s issue of the journal Science.

[…] "We are somehow like an amalgam, a mix of bacteria and human cells. There are some estimates that say 90 percent of the cells on our body are actually bacteria," Steven Gill, a molecular biologist formerly at TIGR and now at the State University of New York in Buffalo, said in a telephone interview.

[…] Gill and his team sequenced the DNA in faeces donated by three adults. They found a surprising amount of it came from bacteria.

They compared the gene sequences to those from known bacteria and to the human genome and found this so-called colon microbiome -- the entire sum of genetic material from microbes in the lower gut - includes more than 60,000 genes.

That is twice as many as found in the human genome. "Of all the DNA sequences in that material, only 1 to 5 percent of it was not bacterial," Gill said. "We were surprised."

[…] Gill said his team hopes now to make a comparison of the gut bacteria from different people. […]

I had a professor once who referred to life on earth as “bacteria and a handful of less important organisms.” Probably not an unreasonable statement from a biological, if not a theological, perspective. Nonetheless, 90 – 99% of the total DNA? Wow. I can’t help thinking that to get that much bacterial DNA out of a human, they must have been examining lawyers…