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J. Bacteriol. doi:10.1128/JB.01270-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The response of Porphyromonas gingivalis to heme limitation in continuous culture

Cooperative Research Centre for Oral Health Science, Melbourne Dental School, Bio21 Institute, The University of Melbourne, Australia; and WHO Collaborating Centre for Reference and Research on Influenza, Parkville, Victoria, Australia

^* To whom correspondence should be addressed. Email: e.reynolds{at}unimelb.edu.au.

	Abstract

Porphyromonas gingivalis is an anaerobic, asaccharolytic Gram-negative bacterium that has essential requirements for both iron and protoporphyrin IX, which it preferentially obtains as heme. A combination of large-scale, quantitative proteomic analysis using stable isotope labelling strategies and mass spectrometry, together with transcriptomic analysis using custom-made DNA microarrays, was used to identify changes in P. gingivalis W50 protein and transcript abundances on changing from heme-excess to heme-limited continuous culture. This approach identified 160 genes and 70 proteins that were differentially regulated by heme availability, with broad agreement between the transcriptomic and proteomic data. A change in abundance of the enzymes of the aspartate and glutamate catabolic pathways was observed with heme limitation which was reflected in organic acid end product levels of the culture fluid. These results demonstrate a shift from an energy-efficient anaerobic respiration to a less efficient process upon heme limitation. Heme limitation also resulted in an increase in abundance of a protein, PG1374 which we have demonstrated, by insertional inactivation, to have a role in epithelial cell invasion. The greater abundance of a number of transcripts/proteins linked to invasion of host cells, oxidative stress response, iron/heme transport and virulence of the bacterium indicate there is a broad response by P. gingivalis to heme availability.