Office: (859) 257-5147
Fax: (859) 257-8994
Lab: (859) 323-3870
Jason Johnston, Ph.D.
Doctoral Studies: University of Alabama at Birmingham.
Postdoctoral: University of Iowa.
My laboratory studies gene regulation and virulence in nontypeable Heamophilus influenzae (NTHi). NTHi is an opportunistic pathogen that is commonly found as part of the normal flora in the human upper respiratory tract. We study transcriptional regulation and attempt to identify genes that are required for virulence, and then determine their role in infection and host-pathogen interactions. We use a wide variety of genetic, biochemical, and physiological methods in the course of our investigations.
Our work in NTHi focuses on biofilm formation, an important feature in middle ear infections. We are investigating how NTHi senses its environment and adapts to the host immune response. Our work has focused on a two-component regulatory system, FirRS, which responds to ferrous iron and zinc. The FirRS system regulates the expression of a previously uncharacterized periplasmic protein that influences iron uptake. This system is important for survival in a lung environment and may have a role in the interaction of NTHi and macrophage cells. Currently, we are studying the expression of the system in vivo and exploring its role in survival in the host and iron transport.
Other projects in the lab look at other aspects of biofilm formation. We are characterizing the regulation of AI-2 uptake, a cell-cell signaling molecule that promotes the maturation of biofilms. AI-2 uptake is mediated by the ribose transporter. Transporter expression is tightly regulated and regulation integrates multiple control mechanisms. Understanding these regulatory mechanisms will aid in the identification of AI-2-regulated genes and allow us to develop a model for the control of biofilm formation.
Selected Recent Publications:
Steele, K. H., L. H. O’Connor, N. Burpo, K. Kohler, and J. W. Johnston. 2012. Characterization of a ferrous iron responsive two-component system in nontypeable Haemophilus influenzae. J. Bacteriol. 194: 6162-6173.
Johnston, J. W. 2012. An improved counterselection cassette for use in Haemophilus influenzae. Gene. 492:325-8.
Johnston, J. W., H. Shamsulddin, A. Miller, and M. A. Apicella. 2010. Sialic acid transport and catabolism are cooperatively regulated by SiaR and CRP in nontypeable Haemophilus influenzae. BMC Microbiol. 10: 240-253.
Johnston, J. W., N. P. Coussens, S. Allen, J. Houtman, K. H. Turner, A. Zaleski, S. Ramaswamy, B. W. Gibson, and M. A. Apicella. 2008. Characterization of the N-acetyl-5-neuraminic acid binding site of the extracytoplasmic solute receptor (SiaP) of nontypeable Haemophilus influenzae strain 2019. J. Biol. Chem. 283: 855-865.
Johnston, J. W., A. Zaleski, S. Allen, J. M. Mootz, D. Armbruster, B. W. Gibson, M. A. Apicella, and R. S. Munson, Jr. 2007. Regulation of sialic acid transport and catabolism in Haemophilus influenzae. Mol. Microbiol. 66: 26-39.
Johnston, J. W., D. E. Briles, L. E. Myers, and S. K. Hollingshead. 2006. Mn2+-dependent regulation of multiple genes in Streptococcus pneumoniae through PsaR and the resultant impact on virulence. Infect. Immun. 74: 1171-1180.
Allen, S., A. Zaleski, J. W. Johnston, B. W. Gibson, and M. A. Apicella. 2005. Novel sialic acid transporter of Haemophilus influenzae. Infect. Immun. 73: 5291-5300.
Johnston, J. W., L. E. Myers, M. M. Oochs, W. H. Benjamin, Jr., D. E. Briles, and S. K. Hollingshead. 2004. Lipoprotein PsaA in virulence of Streptococcus pneumoniae: surface accessibility and role in protection from superoxide. Infect. Immun. 72: 5858-5867.