Joined: Jan. 2006
steve, I am going to use this thread to dump this little article.
|'We are not entirely human'|
02/06/2006 08:35 - (SA)
# Gene map holds disease secrets
Washington - 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.
Their findings suggest that studying bacteria native to our bodies may provide
important clues to disease, nutrition, obesity and how well drugs will work in
individuals, said the team at The Institute for Genomic Research, commonly known
as TIGR, in Maryland.
"We are somehow like an amalgam, a mix of bacteria and human cells. There are
some estimates that say 90% of the cells on our body are actually bacteria,"
Steven Gill, a molecular biologist said.
"We're entirely dependent on this microbial population for our well-being. A
shift within this population, often leading to the absence or presence of
beneficial microbes, can trigger defects in metabolism and development of
diseases such as inflammatory bowel disease."
Scientists have long known that at least 50% of human faeces, and often more, is
made up of bacteria from the gut. Bacteria start to colonise the intestines and
colon shortly after birth, and adults carry up to 100 trillion microbes,
representing more than 1 000 different species.
They are not just freeloading. They help humans to digest much of what we eat,
including some vitamins, sugars, and fibre. They also synthesise vitamins that
"Humans have evolved for million of years with these bacteria. And they provide
essential functions," Gill said.
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 one to five percent of it was
not bacterial," Gill said.
"We were surprised."
They also found a surprising number of Archaea, also known as archaebacteria,
which are genetically distinct from bacteria but which are also one-celled
organisms often found in extreme environments such as hot springs.
The donors were healthy adults. None had taken antibiotics for a year, as these
drugs are known to disturb the bacteria in the body.
Gill said his team hopes now to make a comparison of the gut bacteria from
"The ideal study would be to compare 20 people, 30 people from different ethnic
backgrounds, different diets, drinkers, smokers, and so on, because I think
there are going to be distinct differences," Gill said.