Research projects carried out in the group within campylobacter, bacteriophages and bacterial communities

Genome sequencing of Campylobacter jejuni bacteriophages

To date, the genomes of only 6 Campylobacter jejuni bacteriophages have been published. In this project, we have selected 6 new phages for genome sequencing. These phages interact with different surface components on C. jejuni, and genome comparisons will allow us to study the diversity and similarity of their infection mechanisms and ultimately to identify the receptor-binding protein encoded by these phages.

Participants: Martine C. H. Sørensen, Signe B. Baldvinsson, Jens Hammerl, Stefan Hertwig, Lone Brøndsted

Isolation and characterization of novel Campylobacter jejuni bacteriophages from free-range poultry farms in Denmark

Many C. jejuni phages rely on the highly diverse capsular polysaccharides (CPS) of C. jejuni for infection. In this study we have isolated novel bacteriophages from a large screen of faecal samples collected from free-range poultry farms in Denmark using C. jejuni strains expressing different CPS structures as phage indicator strains. These new isolated phages are currently being characterized and the impact on the applied indicator strain investigated.

Participants: Yilmas Emre Gençay, Martine C. Holst Sørensen, Tina Birk, Signe Berg Baldvinsson, Bjarke Bak Christensen, Lone Brøndsted

Phage resistance development in Campylobacter jejuni

Previous work has identified modification by phase variation of capsular polysaccharide as a phage defense mechanism employed by C. jejuni, but phage resistance can also develop by loss of motility. Here we are investigating the development of phage resistance in various strains of C. jejuni following exposure to different phages. The experiments are carried out both in vitro and in chickens, and are followed by characterization of resistant isolates.

Participants: Signe B. Baldvinsson, Yilmas Emre Gençay, Martine C. Holst Sørensen, Michele R. Richards, Christine M. Szymanski, Lone Brøndsted  

Flagellatropic phage infection of Campylobacter jejuni

To date, only capsular polysaccharides have been identified and characterized as receptors for phage infection in Campylobacter jejuni. In this project, we are investigating a C. jejuni phage, which is dependent on motile flagella for infection. The host interaction of this phages is investigated by confocal fluorescence microscopy and transmission electron microscopy and the phage receptor for the adsorption to the flagella investigated.

Participant: Signe B. Baldvinsson, Martine C. Holst Sørensen, Christina S. Vegge, Lone Brøndsted, Horst Neve

Natural transformation of Campylobacter jejuni

Campylobacter is widely known for its fastidious growth demands and limited stress responses. However, C. jejuni displays remarkably efficient natural transformation and we have shown that this organism is constitutively competent even at environmental conditions not supporting growth. Currently we are investigating the mechanism of DNA uptake and the physiological impact of this energy requiring mechanism.

Participants: Christina S. Vegge, Martine C. H. Sørensen, Signe B. Baldvinsson, Lone Brøndsted, Hanne Ingmer

Campylobacter in bacterial communities

Campylobacter jejuni can efficiently and commensally colonize the avian gut but seems unable to proliferate outside the gastrointestinal environment. Nevertheless, C. jejuni is the primary food borne bacterial pathogen in the developed world, and it is puzzling how this apparently fragile organism can survive the transmission to humans. In this project we are exploring how C. jejuni is affected by the multi-species bacterial communities of its natural environmental niches, i.e. how do the bacteria of the chicken gut affect the survival and transmission of C. jejuni and how do the chicken and human microbiota differently affect the virulence factors of C. jejuni?

Participants: Christina S. Vegge

The affect of non-antibiotic drugs on adapted resistance of Staphylococcus aureus

Large fractions of the Western populations are in prolonged treatment with psychiatric drugs, such as antidepressants or agents against Alzheimer’s or Parkinson’s disease. However, when medicating the human body we are also medicating the microorganisms within the body, since there are several examples of pharmaceutical compounds affecting bacteria. This project studies how widely used psychiatric drugs both positively and negatively affect the antibiotic susceptibility of S. aureus.

Participants: Christina S. Vegge, Stanley Cohen, Hanne Ingmer