Regulon controlled by the GppX hybrid two component system in Porphyromonas gingivalis

Area of Science:

• Microbiology
• Molecular Biology
• Genomics

Background:

• Porphyromonas gingivalis is a periodontal pathogen that must adapt to oral cavity environmental changes.
• Two-component systems are crucial for environmental sensing and response in bacteria.
• GppX is a hybrid two-component system in P. gingivalis with a poorly understood regulatory role.

Purpose of the Study:

• To investigate the regulon controlled by the GppX hybrid system in P. gingivalis.
• To define the specific domains and functions of GppX required for gene regulation.
• To elucidate the role of the GppX-PGN_0151 pathway in P. gingivalis colonization and survival.

Main Methods:

• RNA-sequencing (RNA-Seq) was performed on a ΔGppX mutant to identify differentially expressed genes.
• Complementation studies with mutated GppX proteins were used to assess domain function.
• Electrophoretic mobility shift assays (EMSA) confirmed GppX binding to the PGN_0151 promoter.
• Biofilm formation assays were conducted on wild-type, ΔGppX, and ΔPGN_0151 mutants.

Main Results:

• The absence of GppX (ΔGppX mutant) resulted in the upregulation of 53 genes and downregulation of 37 genes.
• Over 40% of differentially abundant genes encoded hypothetical proteins, suggesting a novel regulatory role for GppX.
• GppX's transmembrane domains, DNA-binding domain, and phosphotransfer residues were all essential for regulating the PGN_0151 gene.
• Both ΔGppX and ΔPGN_0151 mutants exhibited deficiencies in monospecies biofilm formation.

Conclusions:

• The GppX system regulates a novel set of genes in P. gingivalis, including PGN_0151.
• Specific domains and phosphotransfer activity of GppX are critical for its regulatory function.
• The GppX-PGN_0151 regulon plays a significant role in the colonization and survival of P. gingivalis through biofilm formation.