we are 10% human 90% microbes.

[Guest guest]

Gutsy little superstars http://www.telegraphindia.com/1060703/asp/knowhow/story_6420110a.asp Bacteria are our ancestors, tenants and saviours, says Roger Highfield Are you feeling calm? Now listen carefully and don’t panic. You are suffering from a crisis of identity. Scientists believe you are not entirely human. In fact, it’s time to stop thinking of yourself as an individual, or even as a single living

thing. You are a hybrid that consists of only about 10 per cent human cells. The rest of you is made up of microbes. This disconcerting vision, in which even superstars such as Angelina Jolie and Brad Pitt are depicted as “super-organisms”, teeming and complex communities of mostly bacteria on two legs, is the latest in a long line of humbling scientific insights to have knocked man off his pedestal. Anyone who has browsed through the latest research literature is left in no doubt: we should bury the traditional and comforting idea that homo sapiens is somehow “better” than the rest of life on the planet. In the past few days, a study of remarkable rock formations in western Australia has provided a vivid reminder of our earliest forebears. These 3.4 billion-year-old features of the Pilbara region — some looking like

egg cartons, others like crests, waves or upside-down ice-cream cones — are now thought to be the remains of ancient microbial communities that were among the first living things. Abigail Allwood of Macquarie University, Sydney, one of the teams that studied them, is convinced that these formations — stromatolites — are among the great-grandmothers of all life on our planet. But as DNA mutated and evolved over billions of years, it had been thought that we left our microbial origins far, far behind. So far, in fact, that most people now regard our ancestors as worse than an embarrassing relative. They perceive bugs as alien, as a threat to our existence. When it comes to bacteria that lurk in hospitals, toilets and kitchens, we seem to be engaged in an endless war. But in the scientific world, there is a growing awareness that we are much more dependent on this

“simpler” life than we realise. The best-known proponent of this view is Prof Lynn Margulis of the University of Massachusetts, Amherst, who developed the concept of “endosymbiosis”, the idea that our complex cells depend on simpler microbial tenants. At the Institute for Genomic Research in Maryland, Dr Steven Gill and colleagues decided to investigate the genetic recipe of our bacterial tenants — the “colon microbiome” — by collecting faeces from two anonymous, healthy adults: a man and a woman who had gone without antibiotics or other medications for a year (when faeces is unscathed by antibiotics, half of it is bacteria). Dr Gill found that we depend on some ancient organisms from what is called the third domain of life. Using DNA screening methods, his team found a surprising number of archaea, also known as

archaebacteria, which are genetically distinct from bacteria but are also one-celled organisms often found in extreme environments such as hot springs, or basking in salt and acid. 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. “The GI tract has the most abundant, diverse population of bacteria in the human body,” says Dr Gill. “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.” 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 can scavenge hydrogen gas from the gut

— a byproduct of digestion that can kill helpful bacteria — and convert it into methane. 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 functions that your fancy, complicated human cells wouldn’t have a clue how to do. The Daily Telegraph "Our ideal is not the spirituality that withdraws from life but the conquest of life by the power of the spirit." - Aurobindo.

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