A sample of the original penicillin mould grown by Alexander Fleming is to auction at Catherine Southon Auctioneers on July 8.
It's expected to make up to ?�6,000 ($9,298).
Fleming famously discovered Penicillin in 1928, which made the treatment of once fatal diseases routine. He was awarded the Nobel Prize in 1948.
The lot is accompanied by a pair of letters sent by Fleming to his neighbours thanking them for alerting him when they saw burglars breaking into his home.
In one letter, written just three days before he died in 1955, he writes: "I have to thank you for a great service when on Saturday night you scared the burglars and so saved my safe and its contents.
"I should have been very sorry to have lost all the various medals which have been given to me and after this experience I do not trust the safe - they are in the bank.
"I must apologise for my affairs having given you trouble and again thank you for your help."
Another not from his housekeeper explains: "As though you didn't know - but just in case - this said affair is a blob of the original mould of penicillin, not to be confused with Gorgonzola cheese!!!"
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