Involvement of PorK, a component of the type IX secretion system, in Prevotella melaninogenica pathogenicity

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Prevotella melaninogenica is an oral bacterium, often commensal but capable of causing suppurative diseases.
• The role of specific virulence factors and secretion systems in P. melaninogenica pathogenicity remains largely uncharacterized.
• Other periodontal pathogens utilize the type IX secretion system (T9SS) for virulence factor secretion.

Purpose of the Study:

• To investigate the role of the type IX secretion system (T9SS) in the pathogenicity of Prevotella melaninogenica.
• To characterize the function of the T9SS-encoding gene, porK, in P. melaninogenica.

Main Methods:

• Construction of a P. melaninogenica GAI 07411 mutant deficient in the T9SS-encoding gene, porK.
• Assays for hemagglutination, biofilm formation, and protease activity.
• Proteomic analysis of secreted proteins using two-dimensional electrophoresis.
• Infection experiments in mice to assess mortality rates.

Main Results:

• The porK mutant exhibited decreased hemagglutination and biofilm formation compared to the wild-type strain.
• Protease secretion was reduced in the porK mutant, indicated by smaller halos on skim milk agar.
• Two-dimensional electrophoresis revealed fewer secreted proteins in the porK mutant's culture supernatant.
• Mice infected with the porK mutant showed a significantly lower mortality rate than those infected with the wild-type strain.

Conclusions:

• Prevotella melaninogenica utilizes the type IX secretion system (T9SS) to secrete potent virulence factors.
• The T9SS, specifically the porK gene product, plays a significant role in the pathogenicity of P. melaninogenica.
• Targeting the T9SS could be a potential strategy to control P. melaninogenica infections.