P. aeruginosa is a species of bacterium that is widely distributed in the environment and is capable of causing very severe infections in patients with predisposing conditions, such as cystic fibrosis. During infection the bacteria secrete a number of agents termed virulence factors that contribute to the pathogenic process. These include proteins (toxins, proteases and phospholipases) and an iron-chelating compound called pyoverdine. We are using a wide range of biochemical, molecular biological and genetic approaches to study the way in which pyoverdine contributes to infection and how it is made.
(i) Regulation of virulence factor production. We have shown that pyoverdine acts as a signalling molecule to control production of several virulence factors as well as pyoverdine itself. The signalling pathway involves at least four proteins and spans two different membranes. We are using a range of approaches to study how this system works, the interactions between different components of the signalling system, and how this system interacts with other signalling systems within the bacteria.
(ii) How does P. aeruginosa exist in cystic fibrosis? In collaboration with researchers in Australia, we have developed methods for extracting bacterial RNA from samples obtained from cystic fibrosis, and for using this to get a snapshot of how P. aeruginosa exists in the lungs of these patients.
(iii) Enzymes that contribute to infection. A number of enzymes have been identified that are required for P. aeruginosa to cause infection. We are characterising some of the critical enzymes using genetic engineering, microbiological and biochemical approaches.
(iv) Comparative genomics. Different strains of P. aeruginosa make different forms of pyoverdine, and even between strains that make the same kind of pyoverdine there are differences in gene organisation. We are exploring the nature of these differences and how they may have arisen.
We thank the Marsden Fund, administered by the Royal Society of New Zealand, the Australian National Health and Medical Research Council, CureKids and Cystic Fibrosis New Zealand for providing funds that support our research.
Anyone who would like more information about our research should contact Prof Lamont at the address shown above. More information is also available through our publications.
M A Llamas, F Imperi, P Visca, and I L Lamont, Cell-surface signalling in Pseudomonas: Stress responses, iron transport, and pathogenicity, FEMS Microbiology Reviews 2014, Link »
Mark J Calcott, Jeremy G Owen, Iain L Lamont, and David F Ackerley, Biosynthesis of novel pyoverdines by domain substitution in a non-ribosomal peptide synthetase of Pseudomonas aeruginosa., Applied and environmental microbiology 2014, Link »
Angela T Nguyen, Maura J O'Neill, Annabelle M Watts, Cynthia L Robson, Iain L Lamont, Angela Wilks, and Amanda G Oglesby-Sherrouse, Adaptation of Iron Homeostasis Pathways by a Pseudomonas aeruginosa Pyoverdine Mutant in the Cystic Fibrosis Lung., Journal of Bacteriology 2014 vol. 196 (12) pp. 2265-2276, Link »
D W Reid, R Latham, I L Lamont, M Cámara, and L F Roddam, Molecular analysis of changes in Pseudomonas aeruginosa load during treatment of a pulmonary exacerbation in cystic fibrosis, Journal of Cystic Fibrosis 2013 vol. 12 (6) pp. 688-699, Link »
Andrea E Donaldson and Iain L Lamont, Biochemistry changes that occur after death: potential markers for determining post-mortem interval., PLoS ONE 2013 vol. 8 (11) p. e82011, Link »
Anna F Konings, Lois W Martin, Katrina J Sharples, Louise F Roddam, Roger Latham, David W Reid, and Iain L Lamont, Pseudomonas aeruginosa uses multiple pathways to acquire iron during chronic infection in cystic fibrosis lungs., Infection and immunity 2013 vol. 81 (8) pp. 2697-2704, Link »
Andrea Evelyn Donaldson & Iain L Lamont, Estimation of postmortem interval using biochemical markers, Australian Journal of Forensic Sciences , Link »
D W Reid, I L Lamont, D J Smith, A C Badrick, and G J Anderson, Airway Iron in Cystic Fibrosis Is Associated with Increased Inflammation, Enhanced Pseudomonas Aeruginosa Infection and Reduced Airway Ph, Respirology 2013 vol. 18 pp. 62-62,
Margi I Butler, Peter A Stockwell, Michael A Black, Robert C Day, Iain L Lamont, and Russell T M Poulter, Pseudomonas syringae pv. actinidiae from Recent Outbreaks of Kiwifruit Bacterial Canker Belong to Different Clones That Originated in China., PLoS ONE 2013 vol. 8 (2) p. e57464, Link »
D J Smith, G J Anderson, I L Lamont, P Masel, S C Bell, and D W Reid, Accurate assessment of systemic iron status in cystic fibrosis will avoid the hazards of inappropriate iron supplementation., Journal of cystic fibrosis : official journal of the European Cystic Fibrosis Society , Link »
Y Nakatani, I L Lamont, and J.F. Cutfield, Discovery and characterization of a distinctive exo-1,3/1,4β-glucanase from the marine bacterium Pseudoalteromonas sp. strain BB1, Applied and environmental microbiology 2010 vol. 76 (20) pp. 6760-6768, Link »
Draper, R. C., Martin, L. W., Beare, P.A. and Lamont, I. L. Differential proteolysis of sigma regulators controls cell-surface signaling in Pseudomonas aeruginosa. Molecular Microbiology 82: 1444-1453 (2011). (IF 4.8)
Upritchard, H.G., Yang, J., Bremer, P. J., Lamont, I.L. and McQuillan, A. J. Adsorption of enterobactin to metal oxides and the role of siderophores in bacterial adhesion to metals. Langmuir 27: 10587-97 (2011). (IF 4.6)
Martin, L. W., Reid, D. W., Sharples, K. J. and Lamont, I.L. Pseudomonas siderophores in the sputum of patients with cystic fibrosis. Biometals 24: 1059-1067 (2011). (IF 2.3)
Hannauer, M., Yeterian, E. Martin, L. W., Lamont, I.L. and Schalk, I. J. An efflux pump is involved in secretion of newly synthesized siderophore by Pseudomonas aeruginosa. FEBS Lett. 584: 4751-5 (2010). (IF 3.6)
Donaldson, A. E., Lamont, I. L., Cordiner, S. J. and Taylor, M. C. Characterising the dynamics of expirated blood pattern formation using high-speed digital imaging. International Journal of Legal Medicine (manuscript accepted for publication) (2010). (IF 2.7)
Donaldson, A. E., Taylor, M. C., Cordiner, S. J. and Lamont, I. L. Using oral microbial DNA analysis to identify expirated bloodspatter. International Journal of Legal Medicine 124: 569-76 (2010). (IF 2.7)
Yeterian, E., Martin, L. W., Hannauer, M., Lamont, I. L. and Schalk I. J. (Joint corresponding authors). An efflux pump is required for siderophore recycling by Pseudomonas aeruginosa. Environmental Microbiology Reports 2: 412-418 (2010). (IF 4.7)
Mettrick, K. M. and Lamont, I. L. Different roles for anti-sigma factors in siderophore signalling pathways of Pseudomonas aeruginosa. Molecular Microbiology 74: 1257-71 (2009).
Yeterian, E., Martin, L. W., Guillon, L. Joure, L., Lamont, I. L. and Schalk, I. J. Synthesis of the siderophore pyoverdine in Pseudomonas aeruginosainvolves a periplasmic maturation. Amino Acids (epub ahead of print) (2009)
Reid, D. W., Anderson, G. J. and Lamont, I. L. The role of lung iron in determining the bacterial and host struggle in cystic fibrosis. Am J Physiol Lung Cell Mol Physiol 297: L795-802.
Ramsay, J. P., Sullivan, J. T., Jambari, N., Ortori, C. A., Heeb, S., Williams, P., Barrett, D. A., Lamont, I. L. and Ronson, C. W. A LuxRI-family regulator system controls excision and transfer of the Mesorhizobium loti strain R7A symbiosis island by activating expression of two conserved hypothetical genes.Molecular Microbiology 73: 1141-1155 (2009).
Shirley, M. and Lamont, I. L. Role of TonB1 in pyoverdine-mediated signaling in Pseudomonas aeruginosa. J. Bacteriol 191: 5634-5460 (2009)
Schalk, I. J., Lamont I. L. and Cobessi, D. Structure-function relationships in the bifunctional ferri-siderophore FpvA receptor from Pseudomonas aeruginosa. Biometals 22: 671-8 (2009).
Lamont, I. L., Konings, A. F. and Reid, D. W. Iron acquisition by Pseudomonas aeruginosa in the lungs of patients with cystic fibrosis. Biometals 22: 53-60 (2009).
Upritchard, U. G., Cordwell, S. J. and Lamont, I. L. Immunoproteomics to examine cystic fibrosis host interactions with extracellular Pseudomonas aeruginosa proteins. Infection and Immunity 76: 4624-4632 (2008).
Spencer, M. R., Beare, P. A. and Lamont, I. L. Role of cell surface signalling in proteolysis of an alternative sigma factor in Pseudomonas aeruginosa.Journal of Bacteriology 190: 4865-4869 (2008).
Reid, D. W,, Anderson, G. J. and Lamont, I. L. Cystic fibrosis: ironing out the problem of infection? Am J Physiol Lung Cell Mol Physiol. 295: L23-4 (invited editorial) (2008).
Carlton, T. M, Sullivan, J. T., Stuart, G. S., Hutt, K, Lamont, I. L. and Ronson, C. W.. Ferrichrome utilization in a mesorhizobial population: microevolution of a three-locus system. Environmental Microbiology 9: 2923-2932. (2007).
Upritchard, H.G, Yang, J., Bremer, P., Lamont, I.L. and McQuillan, A. J. Adsorption to metal oxides of the Pseudomonas aeruginosa siderophore pyoverdine and implications for bacterial biofilm formation on metals. Langmuir 23: 7189-7195 (2007).
Visca, P., Imperi, F. and Lamont, I. L. Pyoverdine siderophores: from biogenesis to biosignificance. Trends in Microbiology 15: 22-30 (2007)
Diggle, S.P., Matthijs, S., Wright, V. J., Fletcher, M. P., Chabra, S. R., Lamont, I. L., Kong, X., Hider, R. C., Cornelis, P., Cámara, M. and Williams, P. The Pseudomonas aeruginosa 4-Quinolone Signal Molecules HHQ and PQS play multi-functional roles in quorum sensing and iron entrapment. Chemistry and Biology 14: 87-96 (2007)
Wilson, M.J. and Lamont, I.L. Mutational analysis of an extracytoplasmic-function sigma factor to investigate its interactions with RNA polymerase and DNA. Journal of Bacteriology 188: 1935-1942 (2006)
Lamont, I. L, Martin, L. W., Sims, T., Scott, A. and Wallace, M. Characterization of a gene encoding an acetylase required for pyoverdine synthesis in Pseudomonas aeruginosa. Journal of Bacteriology 188: 3149-3152 (2006)
Ramsay, J. P., Sullivan, J. T., Stuart, G. S., Lamont, I. L. and Ronson, C. W. Excision and transfer of the Mesorhizobium loti R7A symbiosis island requires an integrase IntS, a novel recombination directionality factor RdfS, and a putative relaxase RlxS. Molecular Microbiology 62: 723-734 (2006)
Yang, J., Bremer, P. J., Lamont, I. L. and McQuillan, A. J. Infrared spectroscopic studies of siderophore-related hydroxamic acid ligands adsorbed on titanium dioxide. Langmuir 22: 10109-10117 (2006)
James, E. E., Beare, P. A., Martin, L. W. and Lamont, I. L. Mutational analysis of a bifunctional ferri-siderophore receptor and signal transducing protein from Pseudomonas aeruginosa. Journal of Bacteriology 185: 4514-4520 (2005)
Caradoc Davies, T.T., Cutfield, S., Lamont, I.L. and Cutfield, J.F. Crystal structures of Escherichia coli uridine phosphorylase in two native and three complexed forms reveal basis of substrate specificity, induced conformational changes and influence of potassium. Journal of Molecular Biology 337: 337-354 (2004)
Ackerley, D. F. and Lamont, I. L. Characterisation and genetic manipulation of peptide synthetases of Pseudomonas aeruginosa PAO1 in order to generate novel pyoverdines. Chemistry and Biology 11: 971-980 (2004)
Beare, P. A., For, R. J., Martin, L. W. and Lamont, I. L.. Siderophore-mediated cell signalling in Pseudomonas aeruginosa: divergent pathways regulate virulence factor production and siderophore receptor synthesis. Molecular Microbiology 47: 197-205 (2003)
Lamont, I. L. and Martin, L. W. Identification and characterization of novel pyoverdine synthesis genes in Pseudomonas aeruginosa. Microbiology 149: 833-842 (2003)
Ackerley, D. F., Caradoc-Davies, T. T. and Lamont, I. L. Substrate specificity of a non-ribosomal peptide synthetase, PvdD, from Pseudomonas aeruginosa.Journal of Bacteriology 185: 2848-2855 (2003)
Lamont, I.L. Bacterial intercellular signalling and infectious disease. Australian Biochemist 34:4-6 (2003)
McWhirter, M. J., Bremer, P. J., Lamont, I. L. and McQuillan, A. J. Siderophore-mediated covalent bonding to metal (oxide) surfaces during biofilm initiation by Pseudomonas aeruginosa bacteria. Langmuir 19: 3575-3577 (2003)
Lamont, I.L. and Beare, P.A. Iron uptake, cell signalling and gene expression in Pseudomonas aeruginosa. NZ BioScience 12:15-17 (2003)
Lamont, I. L., Beare, P. A., Ochsner, U., Vasil, A. I. and Vasil, M. L. Siderophore-mediated signaling regulates virulence factor production in Pseudomonas aeruginosa. Proc. Natl. Acad. Sci. USA 99: 7072-7077 (2002)
Visca, P., Leoni, L., Wilson, M. J. and Lamont, I. L. Iron transport and regulation, cell signalling and genomics: lessons from Escherichia coli and Pseudomonas. Molecular Microbiology 45: 1177-1190 (2002)