Scientists at Imperial College in London and the University of Oxford, England, sequenced for the first time the genome of the fungus Penicillium Rubens that led the Scottish physician Alexander Fleming to discover Penicillin in 1928.

Fleming's discovery was made accidentally when spores of the fungus, which occurs naturally in the environment, contaminated a petri dish that contained a colony of bacteria of the genus Staphylococcus Aureus. Decades ago, samples of this original population were cryogenically preserved for studies in the future.

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According to Evolutionary Biologist Timothy Barraclough, from Imperial College London and the University of Oxford, “we originally intended to use Alexander Fleming's fungus in a few different experiments. But, to our surprise, we found that no one had sequenced the genome of this original population of Penicillium, despite its historical significance ”.

The obtained genetic sequence was compared to two more recent genomes of Penicillium commercially produced in the USA, allowing researchers to observe how large-scale production affected the genetic structure of the mushroom over the years.

Like bacteria that attack, fungi like Penicillium are also able to evolve rapidly to defend against threats and respond to changes in their environment. Understanding this evolution can be crucial for us: “our research can help inspire innovative solutions to combat antibiotic resistance,” said biologist Ayush Pathak, from Imperial College in London.

The fungus found by Fleming was the origin of the production of penicillin in the United Kingdom, but in the USA it originated in a colony of the same species found in a moldy melon. This strain has undergone mutagenic treatments, such as irradiation with X-rays and UV light, and artificial selection to produce a strain with a high rate of penicillin production.

Barraclough's team compared the genetic sequences of the different strains, analyzing both the genes that encode the enzymes that act in the production of penicillin and those that regulate the production of these same enzymes.

The English and North American samples have the same genes that regulate enzymes, but the North American strain has more copies of them, which can help it produce more penicillin. The genes that encode the enzymes are different. The team believes that this is the result of natural selection, a response of the fungus to the different microbes that live in each of its habitats.

"Industrial penicillin production was concentrated on the quantity produced, and the steps used to artificially increase production led to changes in the number of genes," said Pathak. But it is possible that industrial methods have ignored some solutions to optimize the design of penicillin, and we can learn from these natural responses to the evolution of antibiotic resistance ”.

Source: Science Alert