The Mystery of a Bee Disease

Honey bees are considered the third most important type of ‘livestock’ in the world: Roughly 80 percent of all crops rely on pollination by insects – the lion’s share of which is done by bees. Thus, it is alarming that every year on average up to 30 percent of the bee population doesn’t survive the winter, and that even in the summer, during bee season, the bee population is constantly plagued by different pathogens, some of which cause deadly diseases. One of the most important bee pathogens is the bacterium Paenibacillus larvae, the cause of the so-called American foulbrood (AFB), which occurs world wide, and is a compulsorily notifiable disease. There are approximately 250 outbreaks each year in Germany alone.

American foulbrood is a microbial disease that leads to the complete extinction (rotting away) of bee larvae within a few weeks. The nurse bees infect the larvae by feeding them the spores of the bacteria; adult bees are immune to this illness. Despite the enormous damage caused by this pathogen, the molecular processes behind it are still largely unexplored. Thus, fighting this disease is almost impossible.

The team led by Prof. Dr. Roderich Süssmuth and Institute of Chemistry, TU Berlin and UniCat research fields D4 and E4, and Dr. Elke Genersch, Institute for Bee Research Hohen Neuendorf, have now succeeded in characterizing important metabolic pathways of the bacterium, and thus explain additional important puzzle pieces of the molecular pathogenesis of this deadly bee disease. “In this case, the crucial step lay in addressing the unfamiliar or unique metabolic products of this pathogen,” explained Prof. Dr. Roderich Süssmuth. “The pathogen’s genome had already been completely sequenced. Together with the Institute for Bee Research, we identified a gene sequence that suggested an unusual and new secondary metabolism. This must have played some role in the infection and spread of American foulbrood.” Often these secondary metabolites are essential for the success of the pathogen and are, therefore, well suited as an approach for the development of possible pesticides that can fight the bacteria.

The approach is similar to detective work: Based on the gene sequence some approximate characteristics of the searched-for molecule are derived, for example, the size. Then a bacterial culture is examined for molecules with the searched-for size via mass spectrometry. The fraction whose size approximately corresponds to the expected secondary metabolites are further analysed through a wide variety of methods.

“Thus, we studied the fractions for, among other things their antibacterial effects. Ultimately, we were able to identify a very unusually structured secondary metabolite and clarify the biosynthetic pathway,” said Süssmuth. “Relevant tests show that this antibiotic, dubbed Paenilamicin, is not directly involved in the destruction of bee larvae. Furthermore, indications were found that its antibacterial effects help the bacterium to prevail over other microbial competitors in the gut of the larvae,” explained Süssmuth. Now scientists are studying how this knowledge can be used in the fight against the death of the bees. The substance also has another interesting side effect: the antibacterial properties of the Paenilamicin will be studied for their potential efficacy in human or veterinary medicine.

For more information please contact:

Prof. Dr. Roderich Süssmuth
Rudolf Wiechert Professor of Biological Chemistry
Department of Chemistry, TU Berlin
Straße des 17. Juni 124
10623 BERLIN

GERMANY
Tel.: +49 (0)30 314- 24205

Email: suessmuth(at)chem.tu-berlin.de