Timothy L. Yahr, PhD

Portrait
Professor of Microbiology and Immunology
Director of Graduate Studies

Contact Information

Office
200A Eckstein Medical Research Building
431 Newton Rd
Iowa City, IA 52242
319-335-9688

Lab
200N Eckstein Medical Research Building
431 Newton Rd
Iowa City, IA 52242
319-335-8666

Education

BS, Biology, University of Wisconsin-Stevens Point
MS, Microbiology, Medical College of Wisconsin
PhD, Microbiology, Medical College of Wisconsin
Postdoctoral Fellow, Biochemistry, Dartmouth Medical School

Education/Training Program Affiliations

Biomedical Science Program, Department of Microbiology Graduate Program, Interdisciplinary Graduate Program in Translational Biomedicine, Medical Scientist Training Program

Center, Program and Institute Affiliations

Center for Biocatalysis and Bioprocessing, Center for Gene Therapy of Cystic Fibrosis and other Genetic Diseases

Research Summary

The Yahr laboratory studies virulence properties of the opportunistic pathogen Pseudomonas aeruginosa (Pa) with particular interest in the type III secretion system (T3SS). The T3SS functions like a molecular syringe to inject toxins into eukaryotic host cells. The type II secretion machinery consists of ~30 proteins which form a complex that spans both the inner and outer membranes of the bacterial cell. Expression of the T3SS is highly regulated at the transcriptional and post-transcriptional levels. ExsA is the central regulator and directly activates transcription of all T3SS genes. The DNA-binding activity of ExsA is controlled by a partner-switching mechanism that sequesters ExsA and only releases ExsA upon contact of Pa with host cells. Several additional regulators, including Vfr, MvaT/U, VqsM, and PsrA, contribute to T3SS gene regulation by controlling exsA transcription. Translation of ExsA is also highly regulated and is positively stimulated by RsmA/RsmF and an RNA helicase (DeaD), and inhibited by Hfq and small non-coding RNAs. On a more global scale, T3SS gene expression is coordinated to the metabolic state of the cell, anaerobiosis, biofilm development, and motility. The ultimate goal of the lab is to fully characterize the regulatory circuits controlling T3SS gene expression, determine how those circuits integrate environmental signals into the response, and design therapeutic approaches that interfere with the signaling events.

Publications

Janssen, K. H., Diaz, M. R., Gode, C. J., Wolfgang, M. C. & Yahr, T. L. (2018). RsmV a small non-coding regulatory RNA in Pseudomonas aeruginosa that sequesters RsmA and RsmF from target mRNAs. J Bacteriol, 200(16), e00277-18. PMID: 29866805.

Janssen, K. H., Diaz, M. R., Golden, M., Graham, J. W., Sanders, W., Wolfgang, M. C. & Yahr, T. L. (2018). Functional Analyses of the RsmY and RsmZ Small Noncoding Regulatory RNAs in Pseudomonas aeruginosa. J Bacteriol, 200(11), e00736-17. PMID: 29463606.

Kroken, A. R., Chen, C. K., Evans, D. J., Yahr, T. L. & Fleiszig, S. M. (2018). The Impact of ExoS on Pseudomonas aeruginosa Internalization by Epithelial Cells Is Independent of fleQ and Correlates with Bistability of Type Three Secretion System Gene Expression. MBio, 9(3), e00668-18. PMID: 29717012.

Kroken, A., Chen, C., Evans, D., Yahr, T. L. & Fleiszig, S. (2018). P. aeruginosa internalization into epithelial cells is associated with intracellular triggering of the type three secretion system. ARVO, Honolulu, HI.

Janssen, K. H., Cribbs, J. T., Voelker, D., Slusher, Z., Kazmierczak, B. I. & Yahr, T. L. (2018). Regulation of Pseudomonas aeruginosa type III secretion system by small non-coding sRNAs. Cold Spring Harbor, NY: Regulatory & Non-coding RNAs, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY.

Williams McMackin, E. A., Corley, J. M., Marsden, A. E., Cribbs, J. T. & Yahr, T. L. (2018). VqsM activates Pseudomonas aeruginosa type III secretion gene expression by displacing the NH-S proteins MvaT and MvaU from the exsA promoter region. Madison, WI: Molecular Genetics of Bacteria and Phages Meeting, Madison, WI.

Chakravarty, S., Melton, C. N., Bailin, A., Yahr, T. L. & Anderson, G. G. (2017). Pseudomonas aeruginosa Magnesium Transporter MgtE Inhibits Type III Secretion System Gene Expression by Stimulating rsmYZ Transcription. J Bacteriol, 199(23), e00268-17. PMID: 28847924.

Schulmeyer, K. H., Yahr, T. L. (2017). Post-transcriptional regulation of type III secretion in plant and animal pathogens. Curr Opin Microbiol, 36, 30-36. PMID: 28189908.

Chakravarty, S., Melton, C. N., Yahr, T. L. & Anderson, G. G. (2017). Molecular Mechanism of MgtE mediated Type Three Secretion System Inhibition in Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, New Orleans, LA.

Schulmeyer, K. H., Diaz, M. R., Golden, M., Wolfgang, M. C. & Yahr, T. L. (2017). Functional analyses of the RsmY and RsmZ small non-coding regulatory RNAs in Pseudomonas aeruginosa. Midwest Microbial Pathogenesis Meeting, Notre Dame, IN.

Williams McMackin, E. A., Marsden, A. E., Cribbs, J. T. & Yahr, T. L. (2017). Histone-like proteins MvaT and MvaU inhibit type III secretion in Pseudomonas aeruginosa. Midwest Microbial Pathogenesis Meeting, Notre Dame, IN.

Anantharajah, A., Faure, E., Buyck, J. M., Sundin, C., Lindmark, T., Mecsas, J., Yahr, T. L., Tulkens, P. M., Mingeot-Leclercq, M. P., Guery, B. & Van Bambeke, F. (2016). Inhibition of the Injectisome and Flagellar Type III Secretion Systems by INP1855 Impairs Pseudomonas aeruginosa Pathogenicity and Inflammasome Activation. J Infect Dis, 214(7), 1105-16. PMID: 27412581.

Schulmeyer, K. H., Diaz, M. R., Bair, T. B., Sanders, W., Gode, C. J., Laederach, A., Wolfgang, M. C. & Yahr, T. L. (2016). Primary and Secondary Sequence Structure Requirements for Recognition and Discrimination of Target RNAs by Pseudomonas aeruginosa RsmA and RsmF. J Bacteriol, 198(18), 2458-69. PMID: 27381913.

Marsden, A. E., Intile, P. J., Schulmeyer, K. H., Simmons-Patterson, E. R., Urbanowski, M. L., Wolfgang, M. C. & Yahr, T. L. (2016). Vfr Directly Activates exsA Transcription To Regulate Expression of the Pseudomonas aeruginosa Type III Secretion System. J Bacteriol, 198(9), 1442-50. PMID: 26929300.

Fischer, A., Shanrock, C., Yahr, T. L. & Welsh, M. (2016). Dithiothreitol releases bacteria-laden mucus strains from CF pig tracheas. North American Cystic Fibrosis Meeting, Orlando, FL.

Schulmeyer, K., Diaz, M., Bair, T., Hoinka, J., Przytycka, T., Sanders, W., Gode, C., Laederach, A., Wolfgang, M. & Yahr, T. L. (2016). Primary and secondary sequence structure requirements for recognition and discrimination of target RNAs by Pseudomonas aeruginosa RsmA and RsmF. Intelligent Systems for Molecular Biology, Orlando, FL.

Bailin, A., Yahr, T. L. (2016). The diguanylate cyclase YfiN alters exsA transcription to inhibit expression of the Type III Secretion System in Pseudomonas aeruginosa. Midwest Microbial Pathogenesis Meeting, Champaign, IL.

Chakravarty, S., Bailin, A. M., Yahr, T. L. & Anderson, G. G. (2016). The Pseudomonas aeruginosa magnesium transporter mgtE reduces translation of the Type III Secretion System transcription factor exsA. Midwest Microbial Pathogenesis Meeting, Champaign, IL.

Marsden, A. E., King, J. M., Spies, M. A., Kim, O. K. & Yahr, T. L. (2015). Inhibition of Pseudomonas aeruginosa ExsA DNA-Binding Activity by N-Hydroxybenzimidazoles. Antimicrob Agents Chemother, 60(2), 766-76. PMID: 26574012.

Jorth, P., Staudinger, B. J., Wu, X., Hisert, K. B., Hayden, H., Garudathri, J., Harding, C. L., Radey, M. C., Rezayat, A., Bautista, G., Berrington, W. R., Goddard, A. F., Zheng, C., Angermeyer, A., Brittnacher, M. J., Kitzman, J., Shendure, J., Fligner, C. L., Mittler, J., Aitken, M. L., Manoil, C., Bruce, J. E., Yahr, T. L. & Singh, P. K. (2015). Regional Isolation Drives Bacterial Diversification within Cystic Fibrosis Lungs. Cell Host Microbe, 18(3), 307-19. PMID: 26299432.

Intile, P. J., Balzer, G. J., Wolfgang, M. C. & Yahr, T. L. (2015). The RNA helicase DeaD stimulates ExsA translation to promote expression of the Pseudomonas aeruginosa type III secretion system. J Bacteriol, 197(16), 2664-74. PMID: 26055113.

Ince, D., Sutterwala, F. S. & Yahr, T. L. (2015). Secretion of Flagellar Proteins by the Pseudomonas aeruginosa Type III Secretion-Injectisome System. J Bacteriol, 197(12), 2003-11. PMID: 25845843.

Diaz, M. R., Schulmeyer, K. H., Hoinka, J., Przytycka, T., Wolfgang, M. C. & Yahr, T. L. (2015). Determining the mechanistic basis for differential binding by RsmA and RsmF. ASM Conference on Pseudomonas, Washington, DC.

Bailin, A., Diaz, M. R., Urbanowski, M. L., Intile, P. J., Wolfgang, M. C. & Yahr, T. L. (2015). RsmA-dependent post-transcriptional activation of ExsA synthesis. ASM Conference on Pseudomonas, Washington, DC.

Marsden, A. E., Schubot, F. D. & Yahr, T. L. (2014). Self-association of ExsA is required for occupation of adjacent binding sites on Pseudomonas aeruginosa type III secretion system promoters. J Bacteriol, 196(20), 3546-55. PMID: 25070741.

Marsden, A. E., Yahr, T. L. (2014). Amino-Terminal Residues of ExsA Are Required for Self-Association and Interaction with the ExsD Anti-Activator. General Meeting of the American Society for Microbiology, Boston, MA.

Intile, P. J., Diaz, M. R., Urbanowski, M. L., Wolfgang, M. C. & Yahr, T. L. (2014). The AlgZR Two-Component System Recalibrates the RsmAYZ Posttranscriptional Regulatory System To Inhibit Expression of the Pseudomonas aeruginosa Type III Secretion System. J Bacteriol, 196(2), 357-66. PMID: 24187093.

Intile, P. I., Balzer, G. B., Wolfgang, M. C. & Yahr, T. L. (2014). The RNA-Helicase DeaD activates ExsA translation to promote expression of the Pseudomonas aeruginosa type III secretion system. Midwest Microbial Pathogenesis Meeting, Chicago, IL.

King, J. M., Schesser Bartra, S., Plano, G. & Yahr, T. L. (2013). ExsA and LcrF recognize similar consensus binding sites, but differences in their oligomeric state influence interactions with promoter DNA. J Bacteriol, 195(24), 5639-50. PMID: 24142246.

Heimer, S. R., Evans, D. J., Stern, M. E., Barbieri, J. T., Yahr, T. & Fleiszig, S. M. (2013). Pseudomonas aeruginosa Utilizes the Type III Secreted Toxin ExoS to Avoid Acidified Compartments within Epithelial Cells. PLoS One, 8(9), e73111. PMID: 24058462.

Marden, J. N., Diaz, M. R., Walton, W. G., Gode, C. J., Betts, L., Urbanowski, M. L., Redinbo, M. R., Yahr, T. L. & Wolfgang, M. C. (2013). An unusual CsrA family member operates in series with RsmA to amplify posttranscriptional responses in Pseudomonas aeruginosa. Proc Natl Acad Sci U S A, 110(37), 15055-60. PMID: 23980177.

Olson, M. E., King, J. M., Yahr, T. L. & Horswill, A. R. (2013). Sialic Acid Catabolism in Staphylococcus aureus. J Bacteriol, 195(8), 1779-88. PMID: 23396916.

Berhards, R. C., Marsden, A. E., Esher, S. K., Yahr, T. L. & Schubot, F. D. (2013). Self-trimerization of ExsD limits inhibition of the Pseudomonas aeruginosa transcriptional activator ExsA in vitro. FEBS J, 280(4), 1084-94. PMID: 23279839.

King, J. M., Bartra, S. S., Plano, G. V. & Yahr, T. L. (2013). Reexamining the DNA binding properties of LcrF from Yersinia pestis. General Meeting of the American Society for Microbiology, Denver, CO.

Marsden, A. E., Yahr, T. L. (2013). Residues in the amino-terminal domain of ExsA are required for self-association and interaction with the ExsD anti-activator. Molecular Genetics of Bacteria and Phages Meeting, Madison, WI.

Intile, P. I., Diaz, M. R., Urbanowski, M. L., Wolfgang, M. C. & Yahr, T. L. (2013). The AlgZR two-component system recalibrates the RsmAYZ post-transcriptional regulatory system to inhibit expression of the Pseudomonas aeruginosa type III secretion system. Molecular Genetics of Bacteria and Phages Meeting, Madison, WI.

King, J. M., Brutinel, E. D., Marsden, A. E., Schubot, F. D. & Yahr, T. L. (2012). Orientation of Pseudomonas aeruginosa ExsA monomers bound to promoter DNA and base-specific contacts with the P(exoT) promoter. J Bacteriol, 194(10), 2573-85. PMID: 22408167.

Brutinel, E. D., King, J. M., Marsden, A. E. & Yahr, T. L. (2012). The distal ExsA-binding site in Pseudomonas aeruginosa type III secretion system promoters is the primary determinant for promoter-specific properties. J Bacteriol, 194(10), 2564-72. PMID: 22408165.

Zheng, Z., Ma, D., Yahr, T. L. & Chen, L. (2012). The transiently ordered regions in intrinsically disordered ExsE are correlated with structural elements involved in chaperone binding. Biochem Biophys Res Commun, 417(1), 129-34. PMID: 22138394.

Marsden, A. E., Schubot, F. & Yahr, T. L. (2012). Identification of residues in the Pseudomonas aeruginosa transcriptional activator ExsA involved in self-association and interaction with the inhibitor ExsD. Midwest Microbial Pathogenesis Meeting, Medical College of Wisconsin, Milwaukee, WI.

Diaz, M. R., Urbanowski, M. L., Wolfgang, M. C. & Yahr, T. L. (2012). RsmA exerts a positive regulatory effect on ExsA expression at the post-transcriptional level. Midwest Microbial Pathogenesis Meeting, Medical College of Wisconsin, Milwaukee, WI.

Intile, P. J., Urbanowski, M. L., Wolfgang, M. C. & Yahr, T. L. (2012). The AlgZR two-component system recalibrates the RsmAYZ post-transcriptional regulatory system to inhibit ExsA expression in Pseudomonas aeruginosa ?mucA isolates. Midwest Microbial Pathogenesis Meeting, Medical College of Wisconsin, Milwaukee, WI.

King, J. M., Bartra, S. S., Plano, G. V. & Yahr, T. L. (2012). The transcriptional activators of T3SS gene expression in Pseudomonas aeruginosa, Yersinia pestis, Aeromonas hydrophila, Photorhabdus luminescens, and Vibrio parahaemolyticus recognize a common sequence. Midwest Microbial Pathogenesis Meeting, Medical College of Wisconsin, Milwaukee, WI.

Pezzulo, A. A., Gutiérrez, J., Duschner, K. S., McConnell, K. S., Taft, P. J., Ernst, S. E., Yahr, T. L., Rahmouni, K., Klesney-Tait, J., Stoltz, D. A. & Zabner, J. (2011). Glucose depletion in the airway surface liquid is essential for sterility of the airways. PLoS One, 6(1), e16166. PMID: 21311590.

Diaz, M. R., King, J. M. & Yahr, T. L. (2011). Intrinsic and Extrinsic Regulation of Type III Secretion Gene Expression in Pseudomonas aeruginosa. Front Microbiol, 2, 89. PMID: 21833328.

Diaz, M. R., Urbanowski, M. L., Wolfgang, M. C. & Yahr, T. L. (2011). RsmA exerts a positive regulatory effect on ExsA expression at a post-transcriptional level. General Meeting of the American Society for Microbiology, New Orleans, LA.

Brutinel, E. D., King, J. & Yahr, T. L. (2011). The affinity of ExsA for promoter DNA, promoter strength, and the degree of promoter bending are determined by the distal ExsA binding site of T3SS promoters in Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, New Orleans, LA.

Ahlgren, H., Bauerle, E., Yahr, T. L., Singh, P. & Nguyen, D. (2011). The stringent response controls virulence in Pseudomonas aeruginosa. The 25th Annual North American Cystic Fibrosis Conference, Anaheim, CA.

Jones, A. K., Fulcher, N. B., Balzer, G. J., Urbanowski, M. L., Pritchett, C. L., Schurr, M. J., Yahr, T. L. & Wolfgang, M. C. (2010). Activation of the Pseudomonas aeruginosa AlgU regulon through mucA mutation inhibits cyclic AMP/Vfr signaling. J Bacteriol, 192(21), 5709-17. PMID: 20817772.

Vakulskas, C. A., Brutinel, E. D. & Yahr, T. L. (2010). ExsA recruits RNA polymerase to an extended -10 promoter by contacting region 4.2 of sigma-70. J Bacteriol, 192(14), 3597-607. PMID: 20453093.

Fuchs, E. L., Brutinel, E. D., Jones, A. K., Fulcher, N. B., Urbanowski, M. L., Yahr, T. L. & Wolfgang, M. C. (2010). The Pseudomonas aeruginosa Vfr regulator controls global virulence factor expression through cyclic AMP-dependent and -independent mechanisms. J Bacteriol, 192(14), 3553-64. PMID: 20494996.

Fuchs, E. L., Brutinel, E. D., Klem, E. R., Fehr, A. R., Yahr, T. L. & Wolfgang, M. C. (2010). In vitro and in vivo characterization of the Pseudomonas aeruginosa cyclic AMP (cAMP) phosphodiesterase CpdA, required for cAMP homeostasis and virulence factor regulation. J Bacteriol, 192(11), 2779-90. PMID: 20348254.

Brutinel, E. D., Vakulskas, C. A. & Yahr, T. L. (2010). ExsD inhibits expression of the Pseudomonas aeruginosa type III secretion system by disrupting ExsA self-association and DNA binding activity. J Bacteriol, 192(6), 1479-86. PMID: 20008065.

Anderson, G. G., Yahr, T. L., Lovewell, R. R. & O'Toole, G. A. (2010). The Pseudomonas aeruginosa magnesium transporter MgtE inhibits transcription of the type III secretion system. Infect Immun, 78(3), 1239-49. PMID: 20028803.

Brutinel, E. D., King, J. & Yahr, T. L. (2010). The affinity of ExsA for promoter DNA, promoter strength, and the degree of promoter bending are determined by the distal ExsA binding site of T3SS promoters in Pseudomonas aeruginosa. Midwest Microbial Pathogenesis Meeting, Washington University, St Louis, MO.

Urbanowski, M. L., Balzer, G., Wolfgang, M. C. & Yahr, T. L. (2010). The RsmA and MucA/AlgU Regulatory Systems Independently Control ExsA Expression at the Post-transcriptional Level. General Meeting of the American Society for Microbiology, San Diego, CA.

Urbanowski, M. L., Balzer, G., Wolfgang, M. C. & Yahr, T. L. (2010). The RsmA and MucA/AlgU Regulatory Systems Independently Control ExsA Expression at the Post-transcriptional Level. Midwest Microbial Pathogenesis Meeting, Washington University, St Louis, MO.

Vakulskas, C. A., Brady, K. M. & Yahr, T. L. (2009). Mechanism of transcriptional activation by Pseudomonas aeruginosa ExsA. J Bacteriol, 191(21), 6654-64. PMID: 19717612.

Brutinel, E. D., Vakulskas, C. A. & Yahr, T. L. (2009). Functional domains of ExsA, the transcriptional activator of the Pseudomonas aeruginosa type III secretion system. J Bacteriol, 191(12), 3811-21. PMID: 19376850.

Anderson, G. G., Yahr, T. L. & O'Toole, G. A. (2009). Inhibition of Pseudomonas aeruginosa Toxicity Toward Airway Epithelial Cells. North American Cystic Fibrosis Conference, Minneapolis, MN.

Ince, D., Wang, D., Hopp, C. & Yahr, T. L. (2009). Secretion of flagellar proteins through the Pseudomonas aeruginosa injectisome system. Midwest Microbial Pathogenesis Meeting, West Lafayette, IN.

Jones, A. K., Balzer, G., Yahr, T. L., Fulcher, N. B. & Wolfgang, M. C. (2009). The MucA pathway contributes to reciprocal regulation of acute and chronic virulence factors in Pseudomonas aeruginosa. Mid-Atlantic Microbial Pathogenesis Meeting, Wintergreen Conference Center, VA.

Brutinel, E. D., Vakulskas, C. A., Brady, K. M. & Yahr, T. L. (2008). Characterization of ExsA and of ExsA-dependent promoters required for expression of the Pseudomonas aeruginosa type III secretion system. Mol Microbiol, 68(3), 657-71. PMID: 18373522.

Brutinel, E. D., Yahr, T. L. (2008). Control of gene expression by type III secretory activity. Curr Opin Microbiol, 11(2), 128-33. PMID: 18396449.

Urbanowski, M. L., Yahr, T. L. (2008). Limiting too much of a good thing: a negative feedback mechanism prevents unregulated translocation of type III effector proteins. (Vols. 190). (8), pp. 2643-4. J Bacteriol. PMID: 18083800.

Brutinel, E., Yahr, T. L. (2008). Characterization of ExsA functional domains, the Transcriptional Activator of the Pseudomonas aeruginosa Type III Secretion System. General Meeting of the American Society for Microbiology, Boston, MA.

Brady, K., Yahr, T. L. (2008). Identifying intrinsic structural properties in type III secretion promoters and the role they play in ExsA-dependent transcriptional activation in Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, Boston, MA.

Vakulskas, C., Brady, K. M. & Yahr, T. L. (2008). Mechanism of Transcriptional Activation by Pseudomonas aeruginosa ExsA. Gordon Research Conference on Microbial Toxins and Pathogenesis, Andover, NH.

Vakulskas, C., Yahr, T. L. (2008). Mechanism of Transcriptional Activation of T3SS Promoters in Pseudomonas aeruginosa by ExsA. General Meeting of the American Society for Microbiology, Boston, MA.

Anderson, G., Yahr, T. L. & O'Toole, G. A. (2008). The Pseudomonas aeruginosa Magnesium Transporter MgtE Affects Type III Secretion. North American Cystic Fibrosis Conference, Orlando, FL.

Urbanowski, M. L., Brutinel, E. D. & Yahr, T. L. (2007). Translocation of ExsE into Chinese hamster ovary cells is required for transcriptional induction of the Pseudomonas aeruginosa type III secretion system. Infect Immun, 75(9), 4432-9. PMID: 17635873.

Ashare, A., Monick, M. M., Nymon, A. B., Morrison, J. M., Noble, M., Powers, L. S., Yarovinsky, T. O., Yahr, T. L. & Hunninghake, G. W. (2007). Pseudomonas aeruginosa delays Kupffer cell death via stabilization of the X-chromosome-linked inhibitor of apoptosis protein. J Immunol, 179(1), 505-13. PMID: 17579071.

Wu, Y., Xu, Z., Henderson, F. C., Ryan, A. J., Yahr, T. L. & Mallampalli, R. K. (2007). Chronic Pseudomonas aeruginosa infection reduces surfactant levels by inhibiting its biosynthesis. Cell Microbiol, 9(4), 1062-72. PMID: 17166234.

Zheng, Z., Chen, G., Joshi, S., Brutinel, E. D., Yahr, T. L. & Chen, L. (2007). Biochemical characterization of a regulatory cascade controlling transcription of the Pseudomonas aeruginosa type III secretion system. J Biol Chem, 282(9), 6136-42. PMID: 17197437.

Song, Y., Fairman, J., Sawa, T., Liggitt, D., Yahr, T. L. & Wiener-Kronish, J. (2007). Cationic lipid DNA complexes (CLDC)/PcrV as a vaccine against Pseudomonas aeruginosa pneumonia. Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), San Francisco, CA.

Brutinel, E., Vakulskas, C. & Yahr, T. L. (2007). Characterization of the ExsA Box, a Promoter Element Required for Transcription of Genes Encoding the Pseudomonas aeruginosa Type III Secretion System. General Meeting of the American Society for Microbiology, Toronto, Canada.

Brutinel, E., Vakulskas, C. & Yahr, T. L. (2007). DNA Binding Characteristics of ExsA; The Transcriptional Regulator of Type III Secretion in Pseudomonas aeruginosa. Phage Meeting, Madison, WI.

Jones, A. K., Balzer, G., Yahr, T. L., Fulcher, N. & Wolfgang, M. C. (2007). Mechanism for Reciprocal Regulation of Pseudomonas aeruginosa Virulence Factors that Contribute to Acute and Chronic Respiratory Infection. Mid-Atlantic Microbial Pathogenesis Meeting, Wintergreen, VA.

Yahr, T. L., Wolfgang, M. C. (2006). Transcriptional regulation of the Pseudomonas aeruginosa type III secretion system. Mol Microbiol, 62(3), 631-40. PMID: 16995895.

Lykken, G. L., Chen, G., Brutinel, E. D., Chen, L. & Yahr, T. L. (2006). Characterization of ExsC and ExsD self-association and heterocomplex formation. J Bacteriol, 188(19), 6832-40. PMID: 16980486.

Yahr, T. L. (2006). A critical new pathway for toxin secretion?. (Vols. 355). (11), pp. 1171-2. N Engl J Med. PMID: 16971725.

Dasgupta, N., Ashare, A., Hunninghake, G. W. & Yahr, T. L. (2006). Transcriptional induction of the Pseudomonas aeruginosa type III secretion system by low Ca2+ and host cell contact proceeds through two distinct signaling pathways. Infect Immun, 74(6), 3334-41. PMID: 16714561.

Urbanowski, M. L., Yahr, T. L. (2006). ExsE is translocated into host cells by the Pseudomonas aeruginosa type III secretion system. General Meeting of the American Society for Microbiology, Orlando, FL.

Dasgupta, N., Ashare, A., Hunninghake, G. & Yahr, T. L. (2006). Induction of the Pseudomonas aeruginosa type III secretion system by low Ca2+ and host cell contact proceeds through two distinct signaling pathways. General Meeting of the American Society for Microbiology, Orlando, FL.

Yahr, T. L., Parsek, M. R. (2006). Pseudomonas aeruginosa. In M. Dworkin , S. Falkow , E. Rosenberg , K. Schleifer , E. Stackebrandt (Eds.) The Prokaryotes. pp. 704-13. Springer. DOI: 10.1007/0-387-30746-x_22.

Urbanowski, M. L., Lykken, G. L. & Yahr, T. L. (2005). A secreted regulatory protein couples transcription to the secretory activity of the Pseudomonas aeruginosa type III secretion system. Proc Natl Acad Sci U S A, 102(28), 9930-5. PMID: 15985546.

Urbanowski, M. L., Yahr, T. L. (2005). The ExsE regulatory protein is translocated into host cells by the Pseudomonas aeruginosa type III secretion system. Midwest Microbial Pathogenesis Meeting, Minneapolis, MN.

Yahr, T. L., Greenberg, E. P. (2004). The genetic basis for the commitment to chronic versus acute infection in Pseudomonas aeruginosa. (Vols. 16). (4), pp. 497-8. Mol Cell. PMID: 15546607.

Dasgupta, N., Lykken, G. L., Wolfgang, M. C. & Yahr, T. L. (2004). A novel anti-anti-activator mechanism regulates expression of the Pseudomonas aeruginosa type III secretion system. Mol Microbiol, 53(1), 297-308. PMID: 15225323.

Lykken, G. L., Yahr, T. L. (2004). Role of an anti-activator and an anti-anti-activator in controlling expression of Pseudomonas aeruginosa type III secretion. General Meeting of the American Society for Microbiology, New Orleans, LA.

Dasgupta, N., Wolfgang, M. & Yahr, T. L. (2003). ExsC is required for expression of the Pseudomonas aeruginosa type III secretion system. Pseudomonas 2003 Meeting, Quebec City, Canada.

McCaw, M. L., Lykken, G. L., Singh, P. K. & Yahr, T. L. (2002). ExsD is a negative regulator of the Pseudomonas aeruginosa type III secretion regulon. Mol Microbiol, 46(4), 1123-33. PMID: 12421316.

Yahr, T. L. (2002). ExsD is a negative regulator of type III secretion in Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, Salt Lake City, UT.

Yahr, T. L., Wickner, W. T. (2001). Functional reconstitution of bacterial Tat translocation in vitro. EMBO J, 20(10), 2472-9. PMID: 11350936.

Yahr, T. L., Wickner, W. T. (2001). Investigations of the Escherichia coli twin-arginine protein translocase. General Meeting of the American Society for Microbiology, Orlando, FL.

Yahr, T. L., Wickner, W. T. (2000). Evaluating the oligomeric state of SecYEG in preprotein translocase. EMBO J, 19(16), 4393-401. PMID: 10944122.

Olson, J. C., Fraylick, J. E., McGuffie, E. M., Dolan, K. M., Yahr, T. L., Frank, D. W. & Vincent, T. S. (1999). Interruption of multiple cellular processes in HT-29 epithelial cells by Pseudomonas aeruginosa exoenzyme S. Infect Immun, 67(6), 2847-54. PMID: 10338490.

Sawa, T., Yahr, T. L., Ohara, M., Kurahashi, K., Gropper, M. A., Wiener-Kronish, J. P. & Frank, D. W. (1999). Active and passive immunization with the Pseudomonas V antigen protects against type III intoxication and lung injury. Nat Med, 5(4), 392-8. PMID: 10202927.

Vallis, A. J., Finck-Barbançon, V., Yahr, T. L. & Frank, D. W. (1999). Biological effects of Pseudomonas aeruginosa type III-secreted proteins on CHO cells. Infect Immun, 67(4), 2040-4. PMID: 10085057.

Vallis, A. J., Yahr, T. L., Barbieri, J. T. & Frank, D. W. (1999). Regulation of ExoS production and secretion by Pseudomonas aeruginosa in response to tissue culture conditions. Infect Immun, 67(2), 914-20. PMID: 9916108.

Holder, I. A., Neely, A. N., Yahr, T. L. & Frank, D. W. (1999). Genetic analysis of the type III effectors of P. aeruginosa in the burned mouse model. General Meeting of the American Society for Microbiology, Chicago, IL.

Frank, D. W., Yahr, T. L., Sawa, T., Barbancon-Finck, V. & Wiener-Kronish, J. P. (1999). Type III intoxication and Pseudomonas pathogenesis. Pseudomonas '99: Biotechnology and Pathogenesis, American Society for Microbiology, Maui, Hawaii.

Finck-Barbançon, V., Yahr, T. L. & Frank, D. W. (1998). Identification and characterization of SpcU, a chaperone required for efficient secretion of the ExoU cytotoxin. J Bacteriol, 180(23), 6224-31. PMID: 9829931.

Yahr, T. L., Vallis, A. J., Hancock, M. K., Barbieri, J. T. & Frank, D. W. (1998). ExoY, an adenylate cyclase secreted by the Pseudomonas aeruginosa type III system. Proc Natl Acad Sci U S A, 95(23), 13899-904. PMID: 9811898.

Finck-Barbançon, V., Yahr, T. L. & Frank, D. W. (1998). Characterization of the exoU locus from Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, Atlanta, GA.

Vallis, A. J., Yahr, T. L., Barbieri, J. T. & Frank, D. W. (1998). Contact-mediated regulation of ExoS production by Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, Atlanta, GA.

Yahr, T. L., Vallis, A. J., Hancock, M. K. & Frank, D. W. (1998). ExoY, a novel type III secreted adenylate cyclase from Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, Atlanta, GA.

Sawa, T., Ohara, M., Kurahashi, K., Yahr, T. L., Gropper, M. A., Frank, D. W. & Wiener-Kronish, J. P. (1998). Pathogenesis of acute lung injury caused by Pseudomonas aeruginosa major contribution of type III secretory system. American Federation of Biomedical Research, Biomedicine.

Ohara, M., Sawa, T., Kurahashi, K., Yahr, T. L., Frank, D. W., Wiener-Kronish, J. P. & Gropper, M. A. (1998). Pseudomonas aeruginosa inhibits Fc receptor-mediated phagocytosis. American Federation of Biomedical Research, Biomedicine.

Yahr, T. L., Mende-Mueller, L. M., Friese, M. B. & Frank, D. W. (1997). Identification of type III secreted products of the Pseudomonas aeruginosa exoenzyme S regulon. J Bacteriol, 179(22), 7165-8. PMID: 9371466.

Liu, S., Yahr, T. L., Frank, D. W. & Barbieri, J. T. (1997). Biochemical relationships between the 53-kilodalton (Exo53) and 49-kilodalton (ExoS) forms of exoenzyme S of Pseudomonas aeruginosa. J Bacteriol, 179(5), 1609-13. PMID: 9045820.

Vallis, A. J., Yahr, T. L. & Frank, D. W. (1997). Development of in vitro methodologies to study type III-mediated translocation of Pseudomonas aeruginosa ExoS. Midwest Microbial Pathogenesis Meeting, Ann Arbor, MI.

Yahr, T. L., Vallis, A. J., Friese, M. B., Mende-Mueller, L. M. & Frank, D. W. (1997). Identification and characterization of type III secreted products of the Pseudomonas aeruginosa exoenzyme S region. Midwest Microbial Pathogenesis Meeting, Ann Arbor, MI.

Yahr, T. L., Friese, M. B., Mende-Mueller, L. M. & Frank, D. W. (1997). Pseudomonas aeruginosa encodes homologs to the Yersinia lcrGVHyopBD locus. General Meeting of the American Society for Microbiology, Miami Beach, FL.

Yahr, T. L., Goranson, J. & Frank, D. W. (1996). Exoenzyme S of Pseudomonas aeruginosa is secreted by a type III pathway. Mol Microbiol, 22(5), 991-1003. PMID: 8971719.

Yahr, T. L., Barbieri, J. T. & Frank, D. W. (1996). Genetic relationship between the 53- and 49-kilodalton forms of exoenzyme S from Pseudomonas aeruginosa. J Bacteriol, 178(5), 1412-9. PMID: 8631719.

Liu, S., Knight, D. A., Yahr, T. L. & Barbieri, J. T. (1996). Biochemical properties of the 53-kDa form of Pseudomonas aeruginosa exoenzyme S. General Meeting of the American Society for Microbiology, New Orleans, LA.

Yahr, T. L., Goranson, J. & Frank, D. W. (1996). Exoenzyme S of Pseudomonas aeruginosa is secreted by a type III pathway. General Meeting of the American Society for Microbiology, New Orleans, LA.

Yahr, T. L., Goranson, J. & Frank, D. W. (1996). Exoenzyme S of Pseudomonas aeruginosa is secreted by a type III pathway. Gordon Research Conference on Microbial Toxins and Pathogenesis, Colby-Sawyer College, NH.

Yahr, T. L., Hovey, A. K., Kulich, S. M. & Frank, D. W. (1995). Transcriptional analysis of the Pseudomonas aeruginosa exoenzyme S structural gene. J Bacteriol, 177(5), 1169-78. PMID: 7868588.

Yahr, T. L., Barbieri, J. T. & Frank, D. W. (1995). The genetic relationship between the 49- and 53-kDa forms of exoenzyme S. General Meeting of the American Society for Microbiology, Washington, DC.

Yahr, T. L., Frank, D. W. (1994). Transcriptional organization of the trans-regulatory locus which controls exoenzyme S synthesis in Pseudomonas aeruginosa. J Bacteriol, 176(13), 3832-8. PMID: 8021164.

Kulich, S. M., Yahr, T. L., Mende-Mueller, L. M., Barbieri, J. T. & Frank, D. W. (1994). Cloning the structural gene for the 49-kDa form of exoenzyme S (exoS) from Pseudomonas aeruginosa strain 388. J Biol Chem, 269(14), 10431-7. PMID: 8144626.

Yahr, T. L., Frank, D. W. (1994). Transcriptional analysis of the exoenzyme S structural gene. Gordon Research Conference on Microbial Toxins and Pathogenesis, Colby-Sawyer College, NH.

Hovey, A. K., Yahr, T. L. & Frank, D. W. (1992). Functional analysis of ExsA of Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, Atlanta, GA.

Yahr, T. L., Frank, D. W. (1992). Transcriptional control of the trans-regulatory locus required for exoenzyme S synthesis in Pseudomonas aeruginosa. Gordon Research Conference on Microbial Toxins and Pathogenesis, Colby-Sawyer College, NH.

Yahr, T. L., Frank, D. W. (1992). Transcriptional organization of the exoenzyme S trans-regulatory locus in Pseudomonas aeruginosa. General Meeting of the American Society for Microbiology, Atlanta, GA.