Explore the vast range of titles available.

and belong to the Bacteroidota phylum. Both species inhabit the oral cavity and can be associated with periodontal diseases. To survive, they must uptake heme from the host as an iron and protoporphyrin IX source. Among the best-characterized heme acquisition systems identified in members of the Bacteroidota phylum is the Hmu system, with a leading role played by the hemophore-like HmuY (HmuY ) protein. Theoretical analysis of selected HmuY proteins and spectrophotometric methods were employed to determine the heme-binding mode of the HmuY homolog (HmuY ) and its ability to sequester heme. Growth phenotype and gene expression analysis of were employed to reveal the importance of the HmuY and Hmu system for this bacterium. Unlike in , where HmuY uses two histidines for heme-iron coordination, other known HmuY homologs use two methionines in this process. HmuY is the first characterized representative of the HmuY family that binds heme using a histidine-methionine pair. It allows HmuY to sequester heme directly from serum albumin and HmuY , the HmuY homolog which uses two methionines for heme-iron coordination. In contrast to HmuY , which sequesters heme directly from methemoglobin, HmuY may bind heme only after the proteolytic digestion of hemoglobin. We hypothesize that differences in components of the Hmu system and structure-based properties of HmuY proteins may evolved allowing different adaptations of species to the changing host environment. This may add to the superior virulence potential of over other members of the Bacteroidota phylum.

Periodontitis is caused by Gram-negative bacteria. Porphyromonas gingivalis, a major Gram-negative periodontal pathogen, produces virulence factors such as gingipains, lipopolysaccharide (LPS), and lipoproteins, which contribute to tissue destruction. Ozone ultrafine bubble water (OUFBW) has been studied for its antimicrobial effects against various bacteria and toxin protein inactivation. This present study aimed to explore the effects of OUFBW on P. gingivalis and its virulence factors. OUFBW was generated and applied to P. gingivalis to assess bactericidal activity. OUFBW effects on morphological changes in P. gingivalis and its membrane vesicles (MVs) were analyzed using transmission electron microscopy. Gingipain activities in OUFBW-treated P. gingivalis culture supernatant was tested using fluorogenic substrates and endogenous substrates, E-cadherin and IL-6. Degradation of OUFBW-treated gingipains was analyzed by silver staining and western blotting. Effects of OUFBW on P. gingivalis lipoproteins and LPS were evaluated using HEK-Blue cells expressing Toll-like receptor 2 (TLR2) and TLR4, respectively. Cytotoxicity of OUFBW on human gingival cells was analyzed using an MTT assay. OUFBW disrupted the inner membrane of P. gingivalis , leading to elimination of the bacterium and reduction of MVs. OUFBW also decreased gingipain activities and inhibited gingipain-induced degradation of E-cadherin and IL-6 due to gingipain breakdown. Additionally, OUFBW suppressed lipoprotein-induced TLR2 activation but had no effect on LPS-mediated TLR4 signaling. OUFBW showed low cytotoxicity in human gingival cells. Our findings indicate that OUFBW can sterilize P. gingivalis and inactivate gingipains and lipoproteins. These results suggest that OUFBW would be used to disinfect periodontal treatment instruments.

Probiotics are gaining attention for their benefits as a supplement to improve oral health. This study aimed to evaluate the antibacterial effect of the probiotic Lactobacillus helveticus against Porphyromonas gingivalis , a significant pathogen in periodontal diseases. Antibacterial susceptibility was assessed using the well diffusion assay, with 0.12% chlorhexidine (CHX) served as the positive control. Biofilm biomass was evaluated using crystal violet staining. Cell viability in P. gingivalis treated with L. helveticus was determined using the LIVE/DEAD Baclight bacterial assay via fluorescence microscopy. Ultra-morphological alterations in these cells were further examined using Field Emission Scanning Electron Microscopy. The results indicated that L. helveticus significantly reduced the growth of P. gingivalis . The highest concentration of 10 9 cells/mL achieved the most substantial inhibition in the well diffusion assay, followed by concentrations of 10 8 cells/mL and 10 7 cells/mL, which demonstrated a clear dose-dependent response. Furthermore, biofilms of P. gingivalis treated with L. helveticus exhibited a notable biomass reduction of up to 85% at the highest concentrations. LIVE/DEAD staining confirmed a decreased in cell viability among the treated populations, while FESEM analysis revealed morphological disruptions in P. gingivalis cells treated with L. helveticus . These findings suggest that L. helveticus has a potent antibacterial effect against P. gingivalis , highlighting the need for further research to identify the optimal probiotic strategies that could enhance periodontal health.

Bacteria of the genus, belonging to the Bacteroidota phylum, colonize various host niches in health and disease. As heme auxotrophs, they rely on heme uptake for iron and protoporphyrin IX. A key heme acquisition system in is the Hmu system, where the hemophore-like HmuY protein plays a major role. HmuY coordinates heme-iron using two histidines, whereas other known HmuY proteins produced by other Bacteroidota members prefer a pair of histidine-methionine or two methionines. Some of them bind heme the protoporphyrin ring without heme-iron coordination, similar to the HusA protein. This study used bioinformatics, spectroscopic, and electrophoretic methods to compare the genomic organization of the Hmu system and the structural and functional properties of HmuY proteins within the genus. We revealed variations in the heme-binding properties of proteins belonging to the HmuY family and susceptibility to modifications in their heme-binding pockets. These findings suggest that HmuY proteins may have undergone evolutionary adaptations to enhance bacterial survival in the human microbiome, contributing to dysbiosis and disease development. These evolutionary changes may explain the superior heme-binding ability of HmuY compared to HmuY homologs produced by other species.

Abstract Porphyromonas gingivalis is a Gram-negative oral anaerobe that is involved in the pathogenesis of periodontitis, an inflammatory disease that destroys the tissues supporting the tooth, eventually leading to tooth loss. Porphyromonas gingivalis has can locally invade periodontal tissues and evade the host defence mechanisms. In doing so, it utilizes a panel of virulence factors that cause deregulation of the innate immune and inflammatory responses. The present review discusses the invasive and evasive strategies of P. gingivalis and the role of its major virulence factors in these, namely lipopolysaccharide, capsule, gingipains and fimbriae. Moreover, the role of P. gingivalis as a ‘keystone’ biofilm species in orchestrating a host response, is highlighted.

Abstract Iron and heme are crucial for pathogenic bacteria living in the human host but are not available in free form due to their binding by iron- and heme-sequestering proteins. Porphyromonas gingivalis causes dysbiosis in the oral microbiome and is considered a keystone pathogen in the onset and progression of periodontal diseases. Its ability to infect and multiply in host cells and its presence in distant tissues and fluids highlights its pathogenic versatility and explains the relationship between periodontal diseases and systemic or neurodegenerative diseases. Porphyromonas gingivalis has evolved specialized mechanisms that allow it to thrive in the host under adverse nutrient-limited conditions. This review presents the updated summary of the mechanisms of iron and heme acquisition by P. gingivalis, with a central role played by gingipains and the unique Hmu system. The potential role of other iron and heme acquisition systems, such as Hus and Iht, indicates the importance of the partially conserved heme biosynthesis pathway, involving homologs of the HemN, HemG, and HemH proteins. In light of increasing antibiotic resistance, difficulties with diagnosis, and drug administration, targeting the mechanisms of heme and iron acquisition of P. gingivalis represents a promising target for developing diagnostic tests, preventive or therapeutic strategies. This review presents the heme and iron acquisition mechanisms of periodontopathogen Porphyromonas gingivalis, highlighting the roles of gingipains, the Hmu, Hus, and Iht systems, and a partially conserved heme biosynthesis pathway.

Porphyromonas gingivalis is a causative agent in the onset and progression of periodontal disease. This study aims to investigate the effects of quercetin, a natural plant product, on P. gingivalis virulence properties including gingipain, haemagglutinin and biofilm formation. Antimicrobial effects and morphological changes of quercetin on P. gingivalis were detected. The effects of quercetin on gingipains activities and hemolytic, hemagglutination activities were evaluated using chromogenic peptides and sheep erythrocytes. The biofilm biomass and metabolism with different concentrations of quercetin were assessed by the crystal violet and MTT assay. The structures and thickness of the biofilms were observed by confocal laser scanning microscopy. Bacterial cell surface properties including cell surface hydrophobicity and aggregation were also evaluated. The mRNA expression of virulence and iron/heme utilization was assessed using real time-PCR. Quercetin exhibited antimicrobial effects and damaged the cell structure. Quercetin can inhibit gingipains, hemolytic, hemagglutination activities and biofilm formation at sub-MIC concentrations. Molecular docking analysis further indicated that quercetin can interact with gingipains. The biofilm became sparser and thinner after quercetin treatment. Quercetin also modulate cell surface hydrophobicity and aggregation. Expression of the genes tested was down-regulated in the presence of quercetin. In conclusion, our study demonstrated that quercetin inhibited various virulence factors of P. gingivalis .

Background Rheumatoid arthritis (RA) is characterised by autoimmunity to citrullinated proteins, and there is increasing epidemiologic evidence linking Porphyromonas gingivalis to RA. P gingivalis is apparently unique among periodontal pathogens in possessing a citrullinating enzyme, peptidylarginine deiminase (PPAD) with the potential to generate antigens driving the autoimmune response. Objectives To examine the immune response to PPAD in patients with RA, individuals with periodontitis (PD) and controls (without arthritis), confirm PPAD autocitrullination and identify the modified arginine residues. Methods PPAD and an inactivated mutant (C351A) were cloned and expressed and autocitrullination of both examined by immunoblotting and mass spectrometry. ELISAs using PPAD, C351A and another P gingivalis protein arginine gingipain (RgpB) were developed and antibody reactivities examined in patients with RA (n=80), individuals with PD (n=44) and controls (n=82). Results Recombinant PPAD was a potent citrullinating enzyme. Antibodies to PPAD, but not to Rgp, were elevated in the RA sera (median 122 U/ml) compared with controls (median 70 U/ml; p<0.05) and PD (median 60 U/ml; p<0.01). Specificity of the anti-peptidyl citrullinated PPAD response was confirmed by the reaction of RA sera with multiple epitopes tested with synthetic citrullinated peptides spanning the PPAD molecule. The elevated antibody response to PPAD was abolished in RA sera if the C351A mutant was used on ELISA. Conclusions The peptidyl citrulline-specific immune response to PPAD supports the hypothesis that, as a bacterial protein, it might break tolerance in RA, and could be a target for therapy.

Bacterial behavior and virulence during human infection is difficult to study and largely unknown, as our vast knowledge of infection microbiology is primarily derived from studies using in vitro and animal models. Here, we characterize the physiology of Porphyromonas gingivalis, a periodontal pathogen, in its native environment using 93 published metatranscriptomic datasets from periodontally healthy and diseased individuals. P. gingivalis transcripts were more abundant in samples from periodontally diseased patients but only above 0.1% relative abundance in one-third of diseased samples. During human infection, P. gingivalis highly expressed genes encoding virulence factors such as fimbriae and gingipains (proteases) and genes involved in growth and metabolism, indicating that P. gingivalis is actively growing during disease. A quantitative framework for assessing the accuracy of model systems showed that 96% of P. gingivalis genes were expressed similarly in periodontitis and in vitro midlogarithmic growth, while significantly fewer genes were expressed similarly in periodontitis and in vitro stationary phase cultures (72%) or in a murine abscess infection model (85%). This high conservation in gene expression between periodontitis and logarithmic laboratory growth is driven by overall low variance in P. gingivalis gene expression, relative to other pathogens including Pseudomonas aeruginosa and Staphylococcus aureus. Together, this study presents strong evidence for the use of simple test tube growth as the gold standard model for studying P. gingivalis biology, providing biological relevance for the thousands of laboratory experiments performed with logarithmic phase P. gingivalis. Furthermore, this work highlights the need to quantitatively assess the accuracy of model systems.