(January 17th, 2012) Eighty years ago, Alexander Fleming revolutionised medicine by accidentally discovering the world's first bacteria killer. But recent studies show that there is more to the fungus that launched the antibiotic revolution than initially thought.
After returning from a family holiday, Fleming observed that the bacterial culture he had been studying was contaminated with and destroyed by a fungus. Further studies led Fleming to the conclusion that the fungus was producing a substance that was able to kill a number of disease-causing bacteria.
Later on, scientists in the US identified the fungus as an asexual species named Penicillium chrysogenum and collected a large number of similar strains to look for the one that can produce the largest antibacterial secretions. The winner was a strain derived from a moldy cantaloupe melon, which is still used to produce penicillin today.
Even though Fleming's fungus is arguably the most significant medical achievement of the last century, its exact origin and its relationship with the penicillin-producing industrial strains remain unclear. To gain more insight into the fungal origins, Daniel Henk and his colleagues at Imperial College London took a closer look at fungal samples from air and dust “in and around St Mary’s Hospital where Fleming worked” (which is now a museum) and compared these to samples collected around the world.
They investigated the genetics of all strains by identifying pieces of DNA that are shared by all samples. Surprisingly, this analysis revealed that there was more diversity in what initially was thought to be only one species: P. chrysogenum was indeed composed of four different ones. Henk and his colleagues also observed that the 'asexual' fungus' genome shows evidence of recombination, suggesting that the organism has been having sex even though it has never been seen doing so.
These results are, without a doubt, very intriguing. The genetic information obtained could facilitate the search for fungi with antimicrobial properties: with the DNA sequences of the four species it can be confirmed whether a new collected sample indeed carries something new that could have an impact on the antibiotics industry or whether researchers just have to keep forgetting their staphylococci cultures during their holidays.
Paola Carrillo B.
Photo: www.nobelprize.org