Jacobs University researches alternative strategies
of fighting the plant disease fire blight

Jacobs University now started a research project on alternative methods to combat fire blight, a bacterial disease that afflicts pomaceous fruit plants worldwide. Financed by the Federal Agency for Agriculture and Food (Bundesanstalt für Landwirtschaft und Ernährung) with about 233.000 Euro over a 3-year period the project is headed by Matthias Ullrich, expert in molecular microbiology and plant pathology at Jacobs University. The project is part of a multi-institutional research campaign on fire blight combat without the use of antibiotics, which is coordinated by the Federal Biological Research Centre for Agriculture and Forestry (Biologischen Bundesanstalt für Land- und Forstwirtschaft).

[ Jun 10, 2007]  “Fire blight” of pomaceous fruit plants and related species is a plant disease of worldwide occurrence, which consistently causes huge economical damage both in the agricultural production of apples and pears and the industry of ornamental woody plants. The symptoms, which are caused by the plant pathogenic bacterium Erwinia amylovora, are wilted leaves, twigs, and branches culminating in the die-off of the complete plant. The highly infectious disease spreads very fast and easily through rain, wind or pollinating insects.

In the case of a fire blight outbreak a further spread of the disease often can be only prevented effectively by clearing the complete fruit plantation. Currently efficient prophylaxis is only realized by employing a complex forecast system on infection favoring factors combined with the preemptive use of antibiotics. If used improperly the latter not only can accumulate in food products but also can push the progressive development of antibiotic resistances of pathogenic bacteria – one of the today’s most serious medical threats.

The aim of the research project at Jacobs University is the development of alternatives to the antibiotic treatment of fire blight. The approach of Matthias Ullrichand his research team is based on cell-to-cell communication between single bacterial cells called “Quorum sensing”. Quorum sensing (which means ‘to assess the number capable of acting’) is utilized by bacteria to coordinate processes which would be inefficient if they would be performed by individual cells. The cells produce signal molecules − so-called auto-inductors − which they secrete into their surrounding habitat. Progressive reproduction of the bacteria results in elevated concentrations of the molecular cues in the immediate vicinity of the cells, which reabsorb the autoinductors. If a certain concentration threshold is exceeded, special bacterial genes are activated. In the case of E. amylovora these genes are virulence genes whose products destroy herbal cells thereby supply the bacteria with nutrients. The resulting withering plant tissue leads to the typical disease symptoms of fire blight. Ullrich and his co-workers initially will focus on the detailed analysis of the molecular mechanism of Quorum sensing in E. amylovora. Subsequently they will work on identifying substances inhibiting quorum sensing to cut off the signal distribution between the bacteria.