Overall, they found that the human genome - all the genes in our cells - is but a fraction of what it takes to make a human. The collective bacterial genome in the average person is so large that it contains between 60 and 100 times as many genes as the human genome.
Up to 100 trillion microbes, representing more than 1,000 species, make up a motley "microbiome" that allows humans to digest much of what we eat. We lack the means to break down the food we eat into energy essential for our survival and, while bacteria could survive perfectly well without us, we would be doomed without the toil of bacteria that graze in our guts.
"The GI tract has the most abundant, diverse population of bacteria in the human body," says Dr Gill, now at the State University of New York at Buffalo. "We're entirely dependent on this microbial population for our wellbeing. 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."
Dr Gill suspects the ecology of the human gut is at least as complex as that in soils or seas. It teems with single-celled residents that can make vitamins, such as the B vitamins that we cannot synthesise, and can break down plant sugars, such as xylan and cellobiose (similar to cellulose), which humans could not otherwise digest because we lack the necessary enzymes. Our diet would be limited if we could not: cellobiose, for instance, is a key component of plant cell walls that is found in most edible plants, such as apples and carrots.
Some bacteria in the gut break down chemicals made by plants that could cause cancer or other illnesses if they were not neutralised. Others have the capacity to scavenge hydrogen gas from the gut - a byproduct of digestion that can kill helpful bacteria - and convert it into methane. That makes the intestines a more biologically friendly place, while contributing in sometimes embarrassing and smelly incidents to greenhouse emissions. Our intestinal residents even pay us a kind of rent: bacteria in the gut make generous quantities of an enzyme that facilitates the production of butyryl coenzyme A, a fatty acid that is a favourite food of the cells that line the colon.
In short, these gutsy little helpers keep us alive. You would be nothing without the trillions of microbial minions milling around your large intestine, performing crucial physiological functions that your fancy, complicated human cells wouldn't have a clue how to do. These fabulous bugs are part of our inheritance: babies acquire their gut flora as they pass down the birth canal and take a gulp of their mother's vaginal and faecal flora. It might not be the tastiest of first meals, but it could well be one of the healthiest.
Well, I have suspected as much, when I learnt that microchondria is a bacteria with its own DNA.
And I have always suspected that the our gut bacteria is essential.
That is why I do not take antibiotics unless it is absolutely necessary and never long term.
During my dentist days, I was made aware of the ill health that can occur when someone take tetracycline long term. Tetracycline was used to treat Acne, and is taken over months. It is a broad spectrum antibiotic, so destroys the gut bacteria.
Bacteria are good. That is why I do not believe in buying very toxic household cleaning detergents. I do not believe the home environment has to be sterile. This is something parents with young children forget. They are creating trouble for their kids by protecting them completely against contact with bacteria.
