Bacteria have a high level of internal organization, with a subset of proteins and protein complexes having specific subcellular addresses. Examples of subcellular organization can be seen in chromosomal segregation, appendage localization (such as type IV pili and flagella), and division. Our research, which focuses on the mechanisms used to create and maintain this internal organization, will further increase the understanding of the bacterial physiology and lifecycle. We are investigating membrane proteins of Pseudomonas aeruginosa, a Gram-negative opportunistic pathogen that can infect burn victims and those with cystic fibrosis. P. aeruginosa is also a ubiquitous organism, found widely throughout nature, and as such is very versatile. Using proteomics in combination with mutant strains of P. aeruginosa our lab is identifying and characterizing novel polar and septal membrane proteins. These novel proteins will then be used to study the mechanisms for achieving and maintaining the spatial organization within the bacterial cell.
In addition, we are also investigating a known polar component of the bacterial cell: the chemotaxis complex. Similar chemotaxis-like systems in P. aeruginosa are involved in controlling biofilm formation, twitching motility, and swimming motility. These systems all use methyl-accepting chemotaxis proteins (MCPs) to sense and respond to external signals. Current studies are focused on the mechanism of methylation of the MCPs. In silico studies suggest a mechanism distinct from that seen in a model organism, E. coli. In E. coli, methylation of the MCPs is known to affect signal transduction and the organization of the MCPs at the poles of the cell. In P. aeruginosa, not only is the mechanism of methylation unknown, but also unknown are the effects of methylation on this polar complex.
Bardy SL, Hosking E, Walker E, Strahler J, Andrews P, and Maddock J. DamX is a novel septal protein, and overexpression delays cell division likely through interference with septal peptidoglycan processing. In preparation.
Bardy SL and Maddock JR. (2007) Polar explorations: Recent insights into the polarity of bacterial proteins. Curr. Opin. Microbiol. 10(6): 617-23.
Bardy SL and Maddock JR. (2005) Polar localization of a soluble MCP of Pseudomonas aeruginosa. J. Bacteriol. 187(22): 7840-7844.
Voisin S, Houliston RS, Kelly J, Brisson JR, Watson D, Bardy SL, Jarrell KF and Logan SM. (2005) Identification and characterization of the unique N-linked glycan common to the flagellins and S-layer glycoprotein of Methanococcus voltae. J. Biol. Chem. 280(17): 16586-93.
Bardy SL, Ng SYM, Carnegie D and Jarrell KF. (2005) Site-directed mutagenesis analysis of amino acids critical for activity of the type I signal peptidase of the archaeon Methanococcus voltae. J. Bacteriol. 187(3): 118-91
Bardy SL, Ng SYM, and Jarrell KF. (2004) Recent advances in the structure and assembly of the archaeal flagellum. J. Mol. Microbiol. Biotechnol. 7: 41-51
Bardy SL and Jarrell KF. (2003) Cleavage of preflagellins by an aspartic acid signal peptidase is essential for flagellation in the archaeon Methanococcus voltae. Mol. Microbiol. 50(4): 1339-47.
Bardy SL, Eichler J, and Jarrell KF. (2003) Archaeal signal peptides - a comparitive survey at the genome level. Protein Sci. 12(9):1833-43.
Bardy SL, Ng SY, and Jarrell KF. (2002) Prokaryotic motility structures. Microbiology. 149: 295-304.
Bardy SL, Mori T, Komoriya K, Aizawa SI, and Jarrell KF. (2002) Identification and localization of the flagellins FlaA and FlaB3 of Methanococcus voltae. J. Bacteriol. 184(19): 52223-33.
Bardy SL, and Jarrell KF. (2002) FlaK of the archaeon Methanococcus maripaludis possesses preflagellin peptidase activity. FEMS Microbiol. Lett. 208(1): 53-59.