Assistant Professor-Veterinary and Biomedical Sciences

e-mail: joh04207@umn.edu

Research Interests
Research in my laboratory focuses on the pathogenomics of bacteria causing disease in production animals.  I am interested in better understanding the mechanisms of virulence and antimicrobial resistance employed by bacterial pathogens of poultry, swine, and cattle.  Our lab utilizes genomics-based approaches to answer questions relevant to these topics.  I am also interested in the potential threats that some strains might present towards humans and other animals, or vice versa.  Thus, another area of interest is in the horizontal gene pool and the mechanisms and biology of horizontal gene transfer.  I am particularly interested in better understanding the nature of large plasmids encoding virulence, fitness, and drug resistance.

Selected Publications
Johnson, T.J., Wannemuehler, Y.M., Johnson, S.J., and Nolan, L.K.  2007.  Plasmid Replicon Typing of Commensal and Pathogenic Types of Escherichia coli.  Antimicrob Agents Chemother. 73:1976-1983.

Johnson, T.J., Kariyawasam, S., Wannemuehler, Y.M., Mangiamele, P.M., Johnson, S.J., Doetkott, C., Skyberg, J.A., Johnson, J.R., Lynne, A.L., and Nolan, L.K.  2007.  Genome Sequence of Avian Pathogenic Escherichia coli Strain O1:K1:H7 Shares Strong Similarities with Human ExPEC Genomes.  J Bacteriol. 189”3228-3236.

Skyberg, J.A., Johnson, T.J., Logue, C.M., and Nolan, L.K.  2006.  Acquisition of a Large ColV Plasmid by an Avirulent Escherichia coli Isolate Enhances Its Virulence and Ability to Grow in Human Urine.  Infect Immun. 74:6287-6292.

Johnson, T.J., Johnson, S.J., and Nolan, L.K.  2006.  Complete DNA Sequence of a ColBM Plasmid from an Avian Pathogenic Escherichia coli Suggests that it Evolved from Closely Related ColV Virulence Plasmids.  J Bacteriol. 188:5975-5983.

Kariyawasam, S., Johnson, T.J., and Nolan, L.K.  2006.  Unique DNA Sequences of Avian Pathogenic Escherichia coli Isolates as Determined by Genomic Suppressive Subtractive Hybridization.  FEMS Microbiol Letters 262:193-200.

Johnson, T.J., Siek, K.E., Johnson, S.J., and Nolan, L.K.  2006.  DNA Sequence of a ColV Plasmid and Prevalence of Selected Plasmid-Encoded Virulence Genes Among Avian Escherichia coli.  J Bacteriol. 188:745-788.

Kariyawasam, S., Johnson, T.J., and Nolan, L.K.  2006.  The pap Operon of Avian Pathogenic Escherichia coli Strain APEC O1:K1 is Located on a Novel Pathogenicity Island.  Infect Immun. 74:744-749.

Johnson, T.J., Siek, K.E., Johnson, S.J., and Nolan, L.K.  2005.  DNA Sequence and Comparative Genomics of pAPEC-O2-R, an Avian Pathogenic Escherichia coli (APEC) Transmissible R Plasmid.  Antimicrob Agents Chemother. 49:4681-4688.

Rodriguez-Siek, K., Giddings, C.W., Doetkott, C., Johnson, T.J., and Nolan, L.K.  2005.  Characterizing the APEC Pathotype.  Vet Res. 35:241-256.

Rodriguez-Siek, K.E., Giddings, C.W., Johnson, T.J., Fakhr, M., Doetkott, C., and Nolan, L.K.  2005.  Comparison of Escherichia coli Implicated in Human Urinary Tract Infection and Avian Colibacillosis.  Microbiol. 151: 2097-2110.

Current Funding
Understanding Gallibacterium-Associated Peritonitis in the Commercial Egg Laying Industry.  Midwest Poultry Research Program

Richard B. Rimler Memorial Paper Award Winner, AVMA/AAAP Annual Meeting in Nashville, July 2002

CRWAD Oral Presentation Award in Molecular Biology, Chicago, IL, 2004