The strategies used by bacterial pathogens to establish and maintain themselves in the host represent one of the fundamental aspects of microbial pathogenesis. Characterization of these strategies and the underlying molecular machinery offers new opportunities both to our understanding of how organisms cause disease in susceptible individuals and to the development of novel therapeutic measures designed to undermine or interfere with these determinants of successful survival. With respect to the microbial aetiology of the periodontal diseases, a growing body of evidence suggests that the proteolytic enzymes of Porphyromonas gingivalis represent key survival and, by extrapolation, virulence determinants of this periodontal bacterium. This in turn has led to international efforts to characterize these enzymes at the gene and protein level. Approximately 20 protease genes of P. gingivalis with different names and accession numbers have been deposited in the gene databases and a correspondingly heterogeneous nomenclature system is employed for the products of these genes in the literature. However, it is evident, through comparison of these gene sequences and through gene inactivation studies, that the genetic structure of the proteases of this organism, particularly those with specificity for arginyl and lysyl peptide bonds, is less complicated than originally thought. The major extracellular and surface associated arginine specific protease activity is encoded by 2 genes which we recommend be designated rgpA and rgpB (arg-gingipains A & B). Similarly we recommend that the gene encoding the major lysine specific protease activity is designated kgp (lys-gingipain). These three genes, which account for all the extracellular/surface arginine and lysine protease activity in P. gingivalis, belong to a family of sequence-related proteases and haemagglutinins.

Background: Bacterocins are antimicrobial peptides produced by bacteria with a relatively narrow range of activity against closely related organisms. Subtilosin A is a bacteriocin produced by Bacillus subtilis that has activity against Listeria monocytogenes, which might indicate antimicrobial activity unusual for bacteriocins.Objectives: To examine the antimicrobial activity and factors affecting the activity of subtilosin A against a range of potentially pathogenic bacteria. Methods:The peptide was purified from cultures of B. subtilis and the MIC determined for 18 species of bacteria using a microdilution methodology. The extent of capsule formation was determined using microscopic examination of cells mounted in India ink. Protease mutants of a susceptible bacteria and mild heat shock were used to examine the effect of environmental stress on subtilosin A activity.Results: Subtilosin A proved to have antimicrobial activity against a wide range of bacteria including Gram-positive and Gram-negative bacteria and both aerobes and anaerobes. The peptide was less effective against capsulated forms of two Gram-negative bacteria than the non-capsulated strains of either. Heat shock but not protease activity also altered the effectiveness of the bacteriocin.Conclusions: Subtilosin A has limited antimicrobial activity against a number of human pathogens which, combined with its relative ineffectiveness against some capsulated pathogens, may limit its usefulness as a human therapeutic.

Collagenolytic activity was assessed in a variety of microorganisms with particular emphasis on members of the indigenous oral flora. Organisms were grown in complete and peptide depleted basal anaerobic broth. Cell sonicates and media preparations were assayed for collagenolytic activity using 14C‐labelled collagen in solution and as fibrils. Assay reaction products were evaluated by acrylamide gel electrophoresis. All tested species of Bacteroides, including B. gingivalis, B, melaninogenicus ss. melaninogenicus and intermedius, B. capillus, B. oris, B. thetaiotaomicron, and B. fragilis produced collagenase which was primarily associated with the cell fraction. Collagenolytic activity was also observed in both media and cell sonicates of Actinobacillus actinomycetemcomitans, Strain 511. The Bacteroides and Actinobacillus enzymes were heat labile, inhibited by EDTA and human serum. Enzyme activity appeared to be enhanced when these organisms were grown in peptide depleted medium. Collagenase production by tested species of Bacteroides and A. actinomycetemcomitans (511) was unique among other members of the oral microflora including species of Fusobacterium, Actinomyces, Capnocylophaga, and Selenomonas, which did not demonstrate collagenolytic activity under the same cultural conditions.

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