The Whitchurch Lab

Development of model systems to study bacterial biofilms in mucosal diseases.
It is now increasingly appreciated that bacteria usually live in structures known as biofilms, rather than as free-living (planktonic) forms. A biofilm is a complex of matrix-encased bacteria that live together in organised structures and communicate with one another in a cooperative manner. The majority of chronic bacterial infections are now believed to be attributed to biofilms. Bacteria living in biofilms gain enormous advantages from biofilm formation as they provide protection from environmental stresses and resistance to host defence mechanisms. Bacteria living in biofilms are also notoriously resistant to antibiotics and have altered gene expression patterns when compared with planktonic bacteria. We are establishing novel model systems that mimic human mucosal disease conditions for the study of bacterial biofilms in chronic infections.

Biofilm development by non-typeable Haemophilus influenzae.
Otitis media (OM) is the most frequent reason children in developed countries visit the doctor, are prescribed antibiotics or undergo surgery. The long-term consequences of recurrent acute and chronic OM include problems in behaviour and the development of speech, language and cognitive abilities and decreased quality of life outcomes. It is now apparent that OM with effusion (OME) is a biofilm disease commonly caused by non-typeable Haemophilus influenzae (NTHI). In order to develop targeted interventions to treat OME it is important that we understand the process of biofilm development by NTHI. The aim of this project is to establish assay systems for the genetic analysis of NTHI biofilms in OME. We will use these systems to identify genes that are required for biofilm development by NTHI. This project is supported by the Financial Markets Foundation for Children.

Molecular analysis of a complex chemosensory system of Pseudomonas aeruginosa.
Pseudomonas aeruginosa is an important opportunistic pathogen causing serious and often life-threatening infections in immunocompromised humans and is equipped with a large arsenal of secreted and cell associated virulence factors. The major adhesins of P. aeruginosa which facilitate attachment of the bacterium to host epithelial cells are filamentous structures called type IV pili (tfp). Tfp also mediate a form of solid surface translocation termed twitching motility and are required for biofilm development. Twitching motility in P. aeruginosa is controlled by a complex signal transduction pathway (Chp) which has many modules in common with chemosensory systems that control flagella rotation in bacteria. The P. aeruginosa Chp system is possibly the most complex of its kind yet described in bacteria and possesses many modules that allow for the integration of multiple input and output signals. However, currently very little is known about the intermolecular interactions and signalling events which input into, occur within, and output from this regulatory system. The aim of this project is to elucidate the molecular interactions and signal transduction cascades of this complex regulatory system. This project is supported by the NHMRC and the William Buckland Foundation.

Extracellular DNA production and natural transformation in Pseudomonas aeruginosa.
Many bacteria release large quantities of extracellular DNA (ecDNA) into their environment. A well-characterised role for bacterial ecDNA is the transmission of genetic information via natural transformation. This has important consequences with respect to the spread of antibiotic resistance genes and virulence determinants amongst bacterial populations. It is now evident that ecDNA has a number of other functions. We have found that Pseudomonas aeruginosa uses ecDNA to facilitate biofilm development and colony expansion via twitching motility. This project aims to characterise the role of ecDNA in biofilms and colony expansion; identify and characterise genes involved in the mechanism and regulation of ecDNA production; and identify and characterise genes involved in natural transformation.

Extracellular nucleases of Pseudomonas aeruginosa
It has been established for many years that P. aeruginosa secretes extracellular nucleases. However, the biological role(s) of this activity remains unclear. The recent observation that extracellular DNA of P. aeruginosa is required for biofilm formation raises the possibility that the extracellular nucleases might also play a role in biofilm development and/or dissolution. The P. aeruginosa genome encodes at least 4 putative secreted nucleases. The aim of this project is to characterise each of these nucleases and examine their roles in biofilm development, restriction of DNA uptake and escape from neutrophil extracellular traps.

Characterisation of a highly transmissible strain of Pseudomonas aeruginosa.
Cystic fibrosis (CF) is the most common fatal inherited suppurative lung disease of Caucasian children in Australia. Lung infection with the opportunistic pathogen Pseudomonas aeruginosa is one of the hallmarks of CF, and established P. aeruginosa infection in CF is associated with worsening pulmonary function, increased hospitalisation and reduced life expectancy. Most children with CF acquire their own unique strains from the environment and, except after prolonged contact within families, are unlikely to cross-infect one another. However, recently a virulent, highly transmissible strain of P. aeruginosa has been found to be circulating in CF clinics in Eastern Australia. This strain is now referred to as the Australia epidemic strain pulsotype I (AES-I). The aim of this project is to identify factors that confer increased transmissibility.

Recent Publications

• Whitchurch, C.B. (2006) Type IV pili in Pseudomonas species, pp 139-188, in Pseudomonas Vol IV eds J.L. Ramos and R.J. Levesque; Kluwer Adademic/Plenum Publishers; New York USA.
• Whitchurch, C.B., Beatson, S.A., Comolli, J.C., Jakobsen, T., Sargent, J.L., Bertrand, J.J., West, J., Klausen, M., Waite, L.L., Kang, P.J., Tolker-Nielsesn, T., Mattick, J.S., and Engel, J.L. (2005) Pseudomonas aeruginosa fimL regulates multiple virulence functions by intersecting with Vfr-modulated pathways. Mol Microbiol 55:1357-78
• Whitchurch, C.B., Leech, A.J., Young, M.D., Kennedy, D., Sargent, J.L., Bertrand, J.J., Semmler, A.B.T., Mellick, A.A., Martin, P.R., Alm, R.A., Hobbs, Beatson, S.A., Huang, B, M., Nguyen, L., Comolli, J.C., Darzins, A., Engel, J.N. and Mattick, J.S. (2004) Characterization of a complex chemosensory signal transduction system which controls twitching motility in Pseudomonas aeruginosa Mol Microbiol 52: 873-93
• Huang, B., Ru, K., Yuan, Z., Whitchurch, C.B. and Mattick, J.S (2004) tonB3 is required for normal twitching motility and extracellular assembly of type IV pili. J Bacteriol 186: 4387-9
• Huang, B., Whitchurch, C.B. and Mattick, J.S. (2003) FimX, a multi-domain protein connecting environmental signals to twitching motility in Pseudomonas aeuruginosa. J Bacteriol 185, 7068-76
• Nouwens, A.S., Beatson, S.A. Whitchurch, C.B., Young, M.D., Schweizer, H.P., Willcox, M.M.D.P., Walsh, B.J., Mattick, J.S. and Cordwell, S.J. (2003) Identification of extracellular proteins in Pseudomonas aeruginosa via proteomics: invasive, cytotoxic and quorum sensing aspects. Microbiology 149, 1311-22. Faculty of 1000 ranking Factor 3.0- Recommended
• *Whitchurch, C.B., *Erova, T., Emery, J.A., Sargent, J.L., Harris, Semmler, A.B.T., Young, M.D., Mattick, J.S. and Wozniak, D.J. (2002) Phosphorylation of the Pseudomonas aeruginosa response regulator AlgR is essential for type IV fimbriae-mediated twitching motility. J Bacteriol 184, 4544-54 * equal contribution
• Whitchurch, C.B., Tolker-Nielsen, T., Ragas, P.C., and Mattick, J.S. (2002) Extracellular DNA required for biofilm formation. Science 22, 1487 Faculty of 1000 ranking Factor 8.3- Exceptional
• *Beatson, S.A., *Whitchurch, C.B. Semmler, A.B.T. and Mattick, J.S. (2002) Quorum sensing is not required for twitching motility in Pseudomonas aeruginosa. J Bacteriol 184, 3605-13 * equal contribution. Faculty of 1000 ranking Factor 6.0- Must Read
• Beatson, S.A., Whitchurch, C.B., Sargent, J.L. Levesque, R.C. and Mattick, J.S. (2002) Differential regulation of twitching motility and elastase production by Vfr in Pseudomonas aeruginosa J Bacteriol 184, 3605-13