Pål Johnsen

Visiting Associate Professor Department of Pharmacy University

Education :

2000-2004: MSc (Cand. Scient)/PhD (Doctor Scient.) Department of Medical Biology/University Hospital of North Norway (UNN), University of Tromsø , Norway . Professor Arnfinn Sundsfjord's laboratory.

2004-2007: Post Doc Department of Pharmacy, University of Tromsø, Norway. Professor Kaare M. Nielsen Lab.

My research interests are microbial evolution and population dynamics with an emphasis on horizontal gene transfer, its evolution and role in the adaptation of bacteria their current and novel environments. I am also interested in the different population processes involved in persistence of antibiotic resistant bacteria after the removal of antimicrobial drug selective pressures.  

My research whilst "vacationing" in Bruce Levin's Lab include theoretical and experimental studies of the population dynamics of Bacillus subtilis and the conditions responsible for the evolution and maintenance of competence and transformation.

Publications

Johnsen, P.J., D. Dubnau, and B. R. Levin (2009) Episodic Selection and the Maintenance of Competence and Natural Transformation in Bacillus subtilis  (GENETIC S, In Press) [PDF]

Johnsen P. J ., G. S. Simonsen, Ø. Olsvik, T. Midtvedt, and A. Sundsfjord. 2002. Stability, persistence, and evolution of plasmid-encoded VanA glycopeptide resistance in enterococci in the absence of antibiotic selection in vitro and in gnotobiotic mice. Microb. Drug. Resist . 8: 161-170.

Johnsen P. J ., J. I. Østerhus, H. Sletvold, M. Sørum, H. Kruse, K. Nielsen, G. S. Simonsen, and A. Sundsfjord. 2005. Persistence of animal and human glycopeptide resistant enterococci on two Norwegian poultry farms formerly exposed to avoparcin is associated with a widespread plasmid-mediated vanA-element within a polyclonal Enterococcus faecium population. Appl. Environm. Microbiol. 71: 159-168.

Sletvold H., P. J. Johnsen, G. S. Simonsen, B. Aasnes, A. Sundsfjord, and K. M. Nielsen. 2007. Comparative DNA analysis of two vanA plasmids from Enterococcus faecium strains isolated from poultry and a poultry farmer in Norway. Antimicrob. Agents Chemother. 51: 736-9.

Sørum M., P. J. Johnsen, B. Aasnes, T. Rosvoll, H. Kruse, A. Sundsfjord, and G. S. 2006. Simonsen.Colonisation, persistence, and molecular characterisation of glycopeptide resistant enterococci (GRE) in Norwegian poultry and poultry farmers three to eight years after the ban of avoparcin. Appl. Environm. Microbiol. 72: 516-521.

Nielsen K. M., P. J. Johnsen, and J. D. Van Elsas. Gene transfer and microevolution in soil. 2007, in: Modern Soil Microbiology 2 nd ed. CRC Press, Boca Raton, Chapt. 3, pp. 55-81.

Dahl K. H., D. D. Mater, M.J. Flores, P. J. Johnsen, T. Midtvedt, G. Corthier, and A. Sundsfjord. 2007. Transfer of plasmid and chromosomal glycopeptide resistance determinants occurs more readily in the digestive tract of mice than in vitro and exconjugants can persist stably in vivo in the absence of glycopeptide selection. J. Antimicrob. Chemother. 59: 478-86.

Nielsen K. M., P. J. Johnsen , D. Bensasson, and D. Daffonchio. 2007. Release and persistence of extracellular DNA in the environment. Environ. Biosafety Res. In Press