Projects

• Importance of crops as secondary hosts for human pathogens and plant foods as vectors of bacterial infections and intoxications

The microbiota of lettuce is very diverse and consists of bacteria, yeasts and molds. As lettuce is usually eaten raw, the microbiota of lettuce is highly relevant for consumers. This project will investigate which extrinsic factors have an influence on the composition of the autochthonous microbiota and how a change in the health status of the plant affects the microbiota. Particular attention will be paid to changing climatic conditions and conventional as well as novel production systems.

• Interaction of Listeria monocytogenes with lettuce

Research in recent years has shown that crop plants can act as secondary hosts for human pathogens, and the question arises as to what influence this interaction and the technological processes in food production have on the virulence of pathogens. We are particularly interested in the interaction of the human pathogenic bacterium Listeria monocytogenes with the lettuce plant. Pathogens use similar molecular mechanisms for adhesion to/internalization in crop plants as in the human host. Here, gene regulation in representative strains will be investigated in the presence of the plant. In addition, the influence of the localization of the bacteria on and in the plant will be correlated with the expression of selected genes. Structures identified as relevant will first be confirmed by deletion mutagenesis of the corresponding genes. The interaction of wild-type strains as well as deletion mutants and plants will be evaluated by microscopic methods. Pathogens react to the host by changing their transcription patterns, which leads to altered virulence. Transcriptomics (DualRNASeq) will be used to investigate the adaptation of adhering and/or internalized bacteria and the extent to which this affects the virulence and resistance of the bacteria. Since plants always have an autochthonous microbiota and since it must be assumed that these microorganisms interact directly or indirectly, a network of parameters must be investigated instead of a simple relationship.

• Use of “omics” technologies for the characterization of fermentation organisms and targeted selection of starter cultures

Lactococcus lactis and L. cremoris are starter culture organisms used in the dairy industry for industrial fermentation. Strains of these species are genetically diverse due to their plasmidome. The enzymes of the proteolytic system, which are essential for growth in milk, are also partially plasmid-encoded. It is known from industrial experience that some strains induce the formation of bitter peptides, while others do not. It is unknown which genetic determinants in combination with which environmental conditions, especially elevated calcium levels as they occur in the fermentation of concentrates, induce this phenotype. Based on own results, the hypothesis that calcium has an influence on the formation of bitter peptides by starter cultures that is not due to a different transcription of the genes coding for the enzymes/proteins of the proteolytic system will be investigated. For this purpose, selected genes are modified by site-directed mutagenesis in such a way that the resulting proteins have defects in their catalytic centers. These isogenic mutants are examined in comparison to the wild-type strains with regard to their proteolytic properties.

• Investigation of the microbiota of written artefacts

In the Cluster of Excellence Understanding Written Artefacts, written artefacts are investigated by natural scientists and humanities scholars. The Kairouan Manuscript Project is a network of scientists and conservators dedicated to the preservation, maintenance and expansion of a manuscript collection at the National Laboratory for the Preservation and Conservation of Parchment and Manuscripts (NLPCPM) in Tunisia. As part of this collaboration, our working group is investigating the microbiota of parchments. We aim to find out which microorganisms (bacteria, yeasts and molds) are present on the parchments and to correlate this data with the results of physical and chemical measurements.

• Optimierung der mikrobiologischen Qualität und der physiologischen Eigenschaften von verzehrfertigen Blattsalaten und Kräutern mittels innovativer technologischer Verfahren und molekularbiologischer Analysen.
  01.11.2012-31.05.2016, FEI, AiF 17122 N

• Reduktion der Bitterkeit von fermentierten Milchprodukten mit erhöhtem Calciumgehalt durch Selektion geeigneter Starterkulturen - Einfluss milchendogener und exogener Peptidasen.
  01.10.2017-30.09.2020, FEI, AiF 19688 N

• Zweistufige Fermentation pflanzlicher Rohstoffe zur Herstellung pflanzlicher Alternativen zu Rohwurst und Rohmilchkäse.
  01.09.2021-29.02.2024, FEI, AiF 21931 N
  https://www.fei-bonn.de/gefoerderte-projekte/projektdatenbank/aif-21931-n.projekt

• Establishing a strong and lasting international training network for innovation in food and juice industries: A 4D-research approach for fruit juice processing (HiStabJuice).
  01.11.2020-28.02.2025, European Union’s Marie Skłodowska-Curie Innovative Training Network (ITN), GA No. 956257
  https://www.histabjuice.eu/

• Technologische und mikrobiologische Ansätze zum Einsatz von Starterkulturen bei der industriellen Rohschinkenherstellung.
  01.05.2013-30.06.2016, FEI, AiF 17687 N

• Optimierung von Nachweis und Differenzierung von Salmonella enterica, Cronobacter sakazakii und Bacillus cereus in Milch und Milcherzeugnissen durch den Einsatz von Zellwand-bindenden Phagenproteinen.
  01.11.2010-30.04.2013, FEI, AiF 16756 N

• Backwaren hergestellt mit Sauerteigen aus Amaranth, Buchweizen und Sorghum unter Verwendung universell einsetzbarer und mikrobiologisch stabiler Sauerteigstarter.
  01.04.2007-30.06.2009, FEI, AiF 15188 N