Abstract
BackgroundPorphyromonas gingivalis is a major causative pathogen of chronic periodontitis. Within the inflammatory microenvironment, there exists extreme pH values, elevated temperatures and oxidative stress. Pathogens adapt to these stressful environmental conditions by regulating the transcription of virulence genes, modifying themselves with macromolecules and by aggregating and entering into a biofilm growth phase. Our previous study showed that the P. gingivalis sialidase can help cells obtain sialic acid from the environment, which is used to modify macromolecules on the surface of P. gingivalis cells. In this study, we compared the survival, virulence factors and biofilm formation of a sialidase-deficient strain (ΔPG0352) and the wild-type P. gingivalis W83 strain under various pH values, temperatures and oxidative stress conditions to identify the roles of sialidase in the adaptation of P. gingivalis to stressful conditions.ResultsCompared to the growth of the P. gingivalis W83 strain, the growth of the △PG0352 was more inhibited by oxidative stress (0.25 and 0.5 mM H2O2) and exhibited greater cell structure damage when treated with H2O2 as assessed by transmission electron microscopy. Both Lys-gingipain (Kgp) and Arg-gingipain (Rgp) activities were lower in the ΔPG0352 than those in the P. gingivalis W83 strain under all the assayed culture conditions. The lipopolysaccharide (LPS) activity of the W83 strain was higher than that of the ΔPG0352 under acidic conditions (pH 5.0), but no differences between the strains were observed under other conditions. Compared to the biofilms formed by P. gingivalis W83, those formed by the ΔPG0352 were decreased and discontinuous under acidic, alkaline and oxidative stress conditions.ConclusionCompared to the P. gingivalis W83 strain, the survival, virulence and biofilm formation of the ΔPG0352 were decreased under stressful environmental conditions.
Highlights
Porphyromonas gingivalis is a major causative pathogen of chronic periodontitis
There were no differences between the growth rates of the P. gingivalis W83 and Sialidase-deficient porphyromonas gingivalis strain (ΔPG0352) strains under pH-induced stress. (Fig. 1a)
Compared to the P. gingivalis W83 strain, the ΔPG0352 grew more slowly at final concentrations of 0.25 and 0.5 mM H2O2 (P < 0.05), and there were no significant differences between the two P. gingivalis strains at final concentrations of 0.1 and 1 mM H2O2 (Fig. 1e)
Summary
There exists extreme pH values, elevated temperatures and oxidative stress Pathogens adapt to these stressful environmental conditions by regulating the transcription of virulence genes, modifying themselves with macromolecules and by aggregating and entering into a biofilm growth phase. During the progression of periodontal disease, subgingival microorganisms survive in the inflammatory microenvironment, protecting themselves from the deleterious effects of extreme pH values, elevated temperatures and oxidative stress Microorganisms must overcome these harsh conditions to colonize or invade the host and can cause inflammation. To survive under these stressful microenvironmental conditions, bacteria will undergo cellular and physiological changes that include regulating the transcription of virulence genes, modifying themselves with macromolecules through reactions such as sialylation and glycosylation and by aggregating and entering into a biofilm growth phase. We found that the deletion of PG0352 influenced biofilm formation and capsule biosynthesis and decreased the pathogenicity of P. gingivalis in a mouse subcutaneous abscess model [7]
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