Very small pirrhana
Wild E. coli can be deadly. The strain called E. coli O157:H7 is responsible for tens of thousands of cases in the United States of haemorrhagic colitis, some leading to death. The strain was first detected in 1982 as the causative agent of an outbreak of the disease attributed to undercooked hamburgers.

Gene comparisons between E. coli O157:H7 and the laboratory strain of E. coli show little difference and the strains are thought to have diverged as little as 4.5 million years ago, an eyeblink in evolutionary time. But if the genes are almost identical, then why is one strain deadly and the other one harmless?

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