Abstract
The periodontal pathogen Porphyromonas gingivalis strain W83 displays at least three different surface glycans, specifically two types of lipopolysaccharides (O-LPS and A-LPS) and K-antigen capsule. Despite the importance of K-antigen capsule to the virulence of P. gingivalis, little is known as to how expression of genes involved in the synthesis of this surface glycan is regulated. The genes required for K-antigen capsule synthesis are located in a locus that encodes a number of transcripts, including an operon (PG0104 to PG0121, generating ~19.4-kb transcript) which contains a non-coding 77-bp inverted repeat (77 bpIR) region near the 5'-end. Previously, we identified a 550-nucleotide antisense RNA molecule (designated asSuGR for antisense Surface Glycan Regulator) encoded within the 77-bpIR element that influences the synthesis of surface glycans. In this study, we demonstrate that the DNA-binding response regulator PG0720 can bind the promoter region of asSuGR and activate expression of asSuGR, indicating that PG0720 may indirectly influence transcript levels of the K-antigen capsule operon expressed from the sense strand. The data show that deletion of the PG0720 gene confers a defect in the presentation of surface polysaccharides compared with the parent strain and quantitative RT-PCR (qPCR) analysis determined that the overall expression of genes involved in K-antigen capsule synthesis were down-regulated in the PG0720 mutant. Furthermore, the defects of the PG0720 deletion mutant were restored by complementation. Importantly, the PG0720 deletion mutant showed reduced virulence. Altogether, our data show that the response regulator PG0720 regulates expression of asSuGR, a trans-acting antisense RNA molecule involved in modulating the production of surface polysaccharides in P. gingivalis strain W83. The data provide further evidence that surface glycans are key virulence determinants and significantly advances our understanding of the molecular mechanisms controlling the synthesis of P. gingivalis K-antigen capsule, a key virulence determinant.
Highlights
Periodontal diseases are among the most common chronic biofilm-based infections of humans and are associated with chronic systemic inflammatory disorders
The production of Porphyromonas gingivalis virulence factors, including proteases, adhesins, and surface glycans is influenced by its interactions with other oral bacteria and controlled by an elaborate signaling network of P. gingivalis based on serine/threonine and tyrosine phosphorylation/dephosphorylation [5, 6], extracytoplasmic function (ECF) sigma factors [7,8,9,10], and two-component systems (TCS) [11]
To analyze the quantities of surface polysaccharides presented on the surface of the cell by an ELISA format, colonies of the deletion mutant and the parent strain harboring the empty plasmid or pT-PG0720, and PG0106 mutant were scraped from blood agar plates, normalized by optical density and autoclaved
Summary
Periodontal diseases are among the most common chronic biofilm-based infections of humans and are associated with chronic systemic inflammatory disorders. TCS play an important role in bacterial sensing and responding to changes in the environmental cues. These systems consist of a sensor histidine kinase and a response regulator where an environmental signal activates the autophosphorylation of the histidine kinase on a conserved histidine within its sensor domain, the high-energy phosphate is transferred to a conserved aspartate within the receiver domain of the cognate response regulator [12, 13]. The genome of P. gingivalis strain W83 contains only four TCS pairs, along with one orphan histidine kinase, two orphan response regulators, and one chimeric TCS [14]. The focus of this study was on the response regulator PG0720 in strain W83. Transfer of PG0719 from strain W83 to ATCC 33277 restored growth defects [15]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
