The discovery of penicillin kick-started the antibiotic revolution. But a forensic-style investigation of the lab in which Alexander Fleming discovered the world-famous fungus suggests the Nobel prizewinner鈥檚 find has been misunderstood for 80 years.
Fleming returned from a family vacation in August 1928 to find that a fungus had contaminated the samples of bacteria he had left in his lab, and that it was evidently a bacteria killer. Figuring that the fungus was secreting something that could be useful in treating human bacterial infections, Fleming sent his samples off to researchers in the US. They identified the fungus as and looked for similar strains to find the one that would yield the largest antibiotic secretions. The hero strain came from a mouldy cantaloupe melon, and was tweaked to produce the penicillin used today.
, and their colleagues at Imperial College London took a closer look at the fungal samples still preserved in Fleming鈥檚 lab in London, . They even swabbed his old notebook. They then compared them with fungal samples collected by 300 volunteers around the world.
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Henk and Fisher鈥檚 team investigated the genetics of all the samples by studying certain easily recognised chunks of the genome: these don鈥檛 tend to code for specific proteins, but are characterised by particular repeating patterns of short DNA sequences.
Not one, not two, not three
In the samples that would originally have been classed as 笔.听肠丑谤测蝉辞驳别苍耻尘, the team identified four distinct species 鈥� the original species and three brand new ones. 鈥淭here is so much diversity within what we thought was a single species,鈥� says Henk.
Fleming鈥檚 fungus 鈥� one of the previously unknown species 鈥� appears to be the most common of the four. 鈥淚t鈥檚 likely amongst the most common multicellular organisms on the planet,鈥� says Fisher.
The investigation also revealed that the fungus has two sexes and that its genome carries hallmarks of recombination, suggesting that the organism has been having sex even though it has not be seen doing so. 鈥淭hey鈥檙e having what鈥檚 known as cryptic sex 鈥� sneaky sex,鈥� says Fisher. 鈥淲e can鈥檛 make it happen in the lab 鈥� we can only see evidence that it has happened.鈥�
The team hope their work will help others find new antibiotics. 鈥淲hen the US Department of Agriculture was looking for fungi with antimicrobial properties, it was sampling randomly,鈥� says Henk. He says the new analysis suggests that doing so will simply throw up Fleming鈥檚 species most of the time. In future it will be possible to use the DNA sequences to confirm that wild samples carry something truly new and worth investigating.
Henk and Fisher hope Fleming鈥檚 species will be named Penicillium flemingii, but before it is, they鈥檒l have to convince the rest of the community that the fungus truly is new. at the Technical University of Denmark in Kongens Lyngby has some doubts. Based on his research, he suspects that the species might in fact have already been named 笔.听谤耻产别苍蝉 鈥� five years before Fleming鈥檚 auspicious holiday.
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