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Research areas

The main focus of my research was adaptation and resistance development of pathogenic bacteria to the adverse conditions that they encounter in food systems. The work focused on the analyses of microbial response by molecular biological techniques, and through this approach setting up and testing hypotheses for the involved mechanisms. It was also important for me to set the obtained results in perspective: how significant are the observed effects expected to be "in real life"?

In the most recent projects, we characterised the stress response in Campylobacter jejuni in a project entitled "Food-processing effects on survival and culturability of C. jejuni". In this work we characterised the natural strain diversity in response to food-relevant stresses (e.g. drying) and the molecular basis for differences in phenotype.

In another project, we characterised the response of Listeria monocytogenes to sub-lethal alcohol levels. Such exposure induces attachment of various gram positive bacteria, which is quite the opposite of the purpose of using alcohol for cleaning and disinfection.

In previous projects on biopreservation and bacteriocin resistance in L. monocytogenes, we have characterised mechanisms for high or intermediate resistance to pediocin-type bacteriocins or to nisin. These compounds are antimicrobial peptides that may be used for biopreservation of foods.

The research projects in general comprise use of general microbiological methods (frequencies of natural and developed resistance; associated fitness costs; stability of resistance; cross-resistance to antibiotics; competition between pathogen and lactic acid bacteria; verification in food models) as well as the latest molecular biological techniques, i.e. functional genomics, proteomics and transcriptomics. Gene expression was analysed at the RNA level by RFDD (restriction fragment differential display) or DNA arrays, and at the protein level by 2-D gel electrophoresis; correlation between changed expression and resistance was subsequently investigated by gene inactivation.

In my Ph.D., I characterised replication and incompatibility of theta-replicating plasmids in Lactococcus lactis.