Friend or foe?

E. coli are part of a large family - some bacteria in the group are more dangerous to humans than others

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It is widely known for causing outbreaks of infectious diarrhoea and is currently held responsible for a number of deaths - but some scientists say E. coli has given us the answer to life itself.

"It has given us an understanding of who we are," says Carl Zimmer, who has written a biography of the bacterium.

Even before the first hour of our lives is complete, the bacterium is present in our gut in many cases, crowding out more dangerous organisms.

It lives in most other warm-blooded animals and, for the most part, is harmless.

"But some members of the E. coli family have given the group a bad name," says Mr Zimmer.

“It is an incredibly accomplished microbe, both in and out of the lab”

Carl Zimmer Science writer

Though the strain O104 is causing severe illness and deaths in the current outbreak, there are hundreds of types of E. coli which cause us no problems.

E coli was one of the first organisms to have its genetic code sequenced - deepening our understanding of how DNA works and ultimately increasing our knowledge of how humans function.

As French scientist Jacques Monod is reported to have said, "What is true for E. coli is true for the elephant."

Many of the genetic properties that govern E. coli hold true for ourselves.

Several forms of E. coli have been modified to work for the benefit of mankind. The bacteria are currently replicating in tens of thousands of scientific institutes across the world.

In the 1940s,scientists realised that E. coli could mate and exchange genesThey were also able to make a primitive map of where the bacterium's genes were located - one of the first genetic mapsIn the 1960s, researchers discovered they could splice open a section of DNA inside E. coli, add new genes into the mix and allow the bacteria to replicate with this new combination of genesE. coli modified in this way is the basis of many experiments worldwideIn research, it is engineered so that unnecessary, harmful aspects of it are removedMost bacteria used in research are modified so that they do not survive in our guts

E. coli is used as a micro-factory: given the right instructions, it can be modified to rapidly produce hundreds of genes or specific proteins. It is the ideal workhorse: it is easy to grow, does not require much energy, or demand sophisticated living conditions.

Even more crucial to scientists, it can be modified easily and replicates rapidly.

One of the first successes the bacterium holds to its name is the production of human insulin.

In the 1970s, scientists inserted the genes responsible for coding human insulin into the bacteria and were able to produce vast quantities of the hormone to treat diabetes.