Scientists believe they may have found powerful new antibiotics in fungi that could fight drug-resistant bacteria.
Streptococcus causes diseases such as pneumonia
The protein compound or peptide which lives in a fungus found in northern European pine forests is as powerful as penicillin and vancomycin, they say.
When tested in the lab, "plectasin" killed Streptococcus bacteria including strains that are now resistant to conventional antibiotics.
The Danish and US researchers' findings are published in Nature.
Most of the antibiotics we use today are produced in fungi and certain soil bacteria.
However, no new classes have been discovered from these sources over the last decade.
Dr Robert Lehrer, from the University of California, Los Angeles, along with fellow US researchers from Georgetown University Medical Centre and Danish colleagues from the biotechnology firm Novozymes, said the discovery could open the door to new treatments for a wide number of diseases.
Strep bacteria, including Strep pneumoniae and Strep pyogenes, cause diseases such as meningitis, community-acquired pneumonia, life-threatening blood poisoning or sepsis and flesh destroying skin infections.
Tests in mice showed plectasin was relatively non-toxic and equally effective as vancomycin and penicillin in curing animals with pneumonia and abdominal inflammation caused by Strep pneumoniae.
Dr Lehrer said: "This finding, and the existence of about 200,000 additional species of fungi, opens up a vast universe to explore for novel peptide antibiotics."
If proven to be safe and effective in humans, which is the next step, then plectasin-based antibiotics could be on the market by 2012, he said.
David Livermore, of the Health Protection Agency's Antibiotic Resistance and Reference Laboratory at the Centre for Infections, said: "The results from this study are very interesting, especially the potential for large-scale manufacturing of plectasin.
"However, before we can expect to see any clinical development a lot more work will need to be done.
"For instance, questions as to whether plectasin will work in humans, and in which infection types, and whether it can be altered to make it active against a wider range of bacteria will need to be addressed."
Dr Mark Enright, an expert in infectious diseases at St Mary's Hospital, London, said more work was needed to see if plectasin would work on drug-resistant bacteria that are a problem in hospitals, such as MRSA.
Plectasin is a minature protein molecule belonging to a wider group called defensins.
Humans have defensins in their white blood cells and in their skin, but it is believed that plectasin is more potent and targets certain bacteria more specifically.