An active compound – plectasin – found in fungi and lower animals could well be an effective weapon against hazardous bacteria. Plectasin, a small protein molecule, can even destroy extremely resistant bacteria . Scientists at the Universities of Bonn, Utrecht, Aalborg and of the Danish company Novozymes AS are able to explain how the substance does this. The researchers believe plectasin is a promising lead compound for new antibiotics.

Study results were published in the journal Science on 28th May.

A growing number of bacteria are becoming resistant to antibiotics. This is especially true for MRSA (methicillin-resistant Staphylococcus aureus). Most medications are now ineffective against these MRSA strains . According to estimates, as many as every second patient in America treated by intensive-care medicine comes down with an MRSA infection.

Plectasin could put the doctor back in control. But how exactly does the tiny protein molecule do that? Dr. Tanja Schneider, Professor Hans-Georg Sahl and team have answered these questions together with Danish and Dutch colleagues. Plectasin disrupts the forming of the cell wall in bacteria so that the pathogens can no longer divide.

Plectasin behaves a bit like a thief who steals the stones off a mason.

Professor Sahl explains:

It binds to a cell-wall building block called lipid II and thus prevents it from being incorporated. However, bacteria cannot live without a cell wall. It comes as no surprise that the most famous antibiotic penicillin also inhibits cell-wall synthesis.

Yet plectasin is more similar in its mode of action to another widely used drug, vancomycin. Since the early 1980s, vancomycin had been the drug of choice in combating MRSA. However, a growing number of bacteria have become resistant to vancomycin.

Dr. Tanja Schneider stresses:

However, these strains (that are resistant to Vancomycin) are still susceptible to plectasin.

Nevertheless, there is no permanent solution to the resistance problem even with a new antibiotic .

Schneider added:

It is always just a question of time until the pathogens mutate and become insensitive. It’s a never ending arms race.

Plectasin belongs to the class of defensins. These defence molecules are commonly found in fungi, animals, as well as plants.

Humans produce defensins on their skin and in this way nip infections in the bud.

Dr. Hans-Henrik Kristensen from the Danish company Novozymes AS explains:

Defensins not only kill pathogens but also alert the immune system. So the pharmaceutical industry is setting its hopes on them.

“Plectasin, a Fungal Defensin, Targets the Bacterial Cell Wall Precursor Lipid II”
Tanja Schneider,Thomas Kruse, Reinhard Wimmer,3] Imke Wiedemann, Vera Sass, Ulrike Pag, Andrea Jansen, Allan K. Nielsen, Per H. Mygind, Dorotea S. Raventós, Søren Neve, Birthe Ravn, Alexandre M. J. J. Bonvin, Leonardo De Maria, Anders S. Andersen, Lora K. Gammelgaard, Hans-Georg Sahl, Hans-Henrik Kristensen
Science 28 May 2010: Vol. 328. no. 5982, pp. 1168 – 1172
DOI: 10.1126/science.1185723

Written by Christian Nordqvist