A species
E. coli
Escherichia coli
The quiet gut neighbour used to make medicine for people.
You and the e. coli last shared an ancestor about 4.2 billion years ago (on 1 January, if life's history were one year).
Most people carry this tiny neighbour inside them. Many types live quietly in the large intestine, clinging to the slimy lining. On the tree it sits beside Cyanobacteria, so the two turn out to be distant relatives in the great Bacteria group.
Each cell is a colourless rod, about four times longer than wide and far too small to see with the naked eye. About 500 laid end to end would stretch about 1 millimetre, and each cell is many times narrower than a human hair. Most cells swim with several whip-like tails spread over the surface, and grip with many much shorter hairs. Grown overnight on a plain lab plate, crowds of cells grow into small, round, creamy dots.
Scientists also use harmless lab types as tiny factories. In 1978 they gave these bacteria the human instructions for making insulin. In 1982 this bacteria-made medicine became the first medicine made this way to go on sale.
Gut helpers
Many gut types help break down food and supply vitamin K to the body they live in.
Easy to grow
It can grow with or without oxygen, but grows better with oxygen.
A kinder medicine
Before this bacteria-made version, people with diabetes relied on medicine from pigs and cattle, which could cause allergies. The version made by these bacteria suits the human body better.