Johnsen, Pål Jarle

I am generally interested in bacterial microevolution and we are currently focusing on two main topics.

1.    Factors responsible for reversal of antimicrobial drug resistance in the absence of drug selective pressures.

It is clear that the frequency of antimicrobial drug resistance in the community is associated with the total level of antimicrobial consumption. Not so clear is the association between reduced consumption levels and subsequent reduction in the frequency of resistance. We focus on different processes that may counteract the reversal of antimicrobial resistance in drug free environments such as the biological cost of resistance, horizontal gene transfer, and genetic stability of resistance determinants.

2.    The evolution and maintenance of competence for natural genetic transformation.

Horizontal gene transfer (HGT) in bacteria plays a major role in adaptive evolution. This is exemplified through the evolution, spread and selection for antibiotic resistance determinants.  However, this ability to acquire genes from without or to explore the fitness landscape may not have been the selective force responsible for the evolution and maintenance for the capacity to exchange genes. For two out of three described mechanisms of HGT, conjugation and transduction, gene recruitment through recombination is a coincidental byproduct of plasmids’ and phages’ need for continuous transmission to new hosts. The third mechanism of HGT, natural transformation, is a complex mechanism for DNA uptake that requires the concerted action of many chromosomal genes. On first consideration it appears evident that this mechanism for HGT has evolved to sample the available sequence space in order to increase the adaptation rates of transformable strains. However, other hypotheses exist for both the evolution and the maintenance of natural transformation in bacteria. We are currently testing a number of these hypotheses both experimentally and theoretically.

Students and staff:

Postdoc Klaus Harms

Posdoc Nils Hulter

Ph D. Student Vidar Sørum

PhD Student Ane Utnes

Master of Pharmacy student Asbjørn Lunnan

Technician (part time) Kristina Borch-Pedersen (Msc)

Project collaborators Tromsø (ongoing):

Prof Kaare M. Nielsen

Ass. Prof Raul Primicerio

Dr. Ørjan Samuelsen (University hospital North Norway)

Dr. Gunnar S. Simonsen (University hospital North Norway)

International collaborators (ongoing)

Prof. Bruce Levin, Emory University, USA

Ass. Prof. Jeffrey Townsend, Yale University, USA

Lecturer, PhD, Adam Roberts, University College of London, Eastman Dental Institute, UK

Dr. Guido Werner, Robert Koch Institute, Wernigerode, Germany

CV AND CURRENT POSITION

2000-2004
Ph.D. Student
Supervisors Prof. Arnfinn Sundsfjord, Dr. Med. Gunnar Skov Simonsen

2004-2008
Post Doctoral Fellowship. Department of Pharmacology. Prof. Kaare M. Nielsen Lab, Institute of Pharmacy, University of Tromsø, Norway.

2007-2008 
Visiting Post Doc. Bruce Levin Lab. Emory University, Atlanta, USA

2008- Associate Professor of Microbiology. Research group for Microbiology, pharmaco- and molecular epidemiology, Department of Pharmacy, University of Tromsø. Group leader: Prof. Kaare M. Nielsen.