Phylogenetic diversity in fim and mfa gene clusters between Porphyromonas gingivalis and Porphyromonas gulae, as a potential cause of host specificity

Exploring the genetic and functional diversity of Porphyromonas gingivalis long fimbriae

Porphyromonas gingivalis is a key pathobiont in periodontitis. Its long fimbriae consist of a single anchor (FimB), a varying number of stalk (FimA), and three accessory (tip-related) proteins (FimC, FimD, and FimE). Based on 133 strains/genomes available, it was our aim to investigate the diversity within FimA and FimB and explain the variety of long fimbriae (super-)structures. Combining the new forward primer fimAnewF with the established fimAunivR, we were able to amplify and sequence fimA including its leader region covering all genotypes and serotypes for phylogenetic analysis. We designed two primer pairs sensing the presence of an internal stop codon in fimB with an impact on fimbrial length. Finally, we examined fimbrial secondary structures by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The phylogeny of fimA/FimA revealed two new subtypes (IIa and IIb) with specific changes in functional domains and thus adding to the current classification scheme (I, Ib, and II-V). Regarding evolution, we confirm that Porphyromonas gulae fimA-type A is closely related to human P. gingivalis strains of cluster Ib and might be its ancestor genotype. A fimB internal stop codon is rare and was found in ATCC 33277 only. Comparing P. gingivalis TEM/SEM pictures of type I ATCC 33277 with type V OMI622 revealed a broad spectrum of fimbrial structures including bundling, cell-cell knotting, and brick-wall formation. In conclusion, FimA forms more distinct subtypes than previously known. The bundling of long fimbriae, a mechanism known from EPEC/EHEC and Salmonella, is proposed and supported by TEM/SEM pictures for the first time here. The role and variations of terminal accessory FimC-E in superstructure formation and/or (co-) adhesion should be investigated more closely next.

Prevalence and Phylogenetic Analysis of Lipoprotein-Gene ragB-1 of Porphyromonas gingivalis-A Pilot Study

Porphyromonas gingivalis (P.g.) is a key pathogen involved in periodontal diseases. The aim of this study was to investigate the prevalence and phylogenetic origin of the lipoprotein-gene ragB in its most virulent variant, ragB-1 (co-transcribed with ragA-1 as locus rag-1), in different P.g. strains collected worldwide. A total of 138 P.g. strains were analyzed for the presence of ragB-1 by pooled analysis and subsequently individual PCRs. Sequencing a core fragment of ragB-1 of the individual strains made it possible to carry out a phylogenetic classification using sequence alignment. In total, 22 of the 138 P.g. strains tested positive for ragB-1, corresponding to a prevalence of 16%. The fragment investigated was highly conserved, with variations in the base sequence detected in only three strains (OMI 1072, OMI 1081, and OMI 1074). In two strains, namely OMI 1072 (original name: I-433) and OMI 1081 (original name: I-372), which originate from monkeys, two amino-acid alterations were apparent. Since ragB-1 has also been found in animal strains, it may be concluded that rag-1 was transferred from animals to humans and that this originally virulent variant was weakened by mutations over time so that new, less virulent, adapted commensal versions of rag (rag-2, -3, and -4), with P.g. as the host, evolved.

Phylogenomic analysis of the Porphyromonas gingivalis - Porphyromonas gulae duo: approaches to the origin of periodontitis

Porphyromonas gingivalis is an oral human pathogen associated with the onset and progression of periodontitis, a chronic immune-inflammatory disease characterized by the destruction of the teeth-supporting tissue. P. gingivalis belongs to the genus Porphyromonas, which is characterized by being composed of Gram-negative, asaccharolytic, non-spore-forming, non-motile, obligatory anaerobic species, inhabiting niches such as the oral cavity, urogenital tract, gastrointestinal tract and infected wound from different mammals including humans. Among the Porphyromonas genus, P. gingivalis stands out for its specificity in colonizing the human oral cavity and its keystone pathogen role in periodontitis pathogenesis. To understand the evolutionary process behind P. gingivalis in the context of the Pophyoromonas genus, in this study, we performed a comparative genomics study with publicly available Porphyromonas genomes, focused on four main objectives: (A) to confirm the phylogenetic position of P. gingivalis in the Porphyromonas genus by phylogenomic analysis; (B) the definition and comparison of the pangenomes of P. gingivalis and its relative P. gulae; and (C) the evaluation of the gene family gain/loss events during the divergence of P. gingivalis and P. gulae; (D) the evaluation of the evolutionary pressure (represented by the calculation of Tajima-D values and dN/dS ratios) comparing gene families of P. gingivalis and P. gulae. Our analysis found 84 high-quality assemblies representing P. gingivalis and 14 P. gulae strains (from a total of 233 Porphyromonas genomes). Phylogenomic analysis confirmed that P. gingivalis and P. gulae are highly related lineages, close to P. loveana. Both organisms harbored open pangenomes, with a strong core-to-accessory ratio for housekeeping genes and a negative ratio for unknown function genes. Our analyses also characterized the gene set differentiating P. gulae from P. gingivalis, mainly associated with unknown functions. Relevant virulence factors, such as the FimA, Mfa1, and the hemagglutinins, are conserved in P. gulae, P. gingivalis, and P. loveana, suggesting that the origin of those factors occurred previous to the P. gulae - P. gingivalis divergence. These results suggest an unexpected evolutionary relationship between the P. gulae - P. gingivalis duo and P. loveana, showing more clues about the origin of the role of those organisms in periodontitis.

Structural and antigenic characterization of a novel genotype of Mfa1 fimbriae in Porphyromonas gingivalis

Background

Mfa1 fimbriae of the periodontal pathogen Porphyromonas gingivalis are responsible for biofilm formation and comprise five proteins: Mfa1-5. Two major genotypes, mfa170 and mfa153, encode major fimbrillin. The mfa170 genotype is further divided into the mfa170A and mfa170B subtypes. The properties of the novel mfa170B remain unclear.

Methods

Fimbriae were purified from P. gingivalis strains JI-1 (mfa170A), 1439 (mfa170B), and Ando (mfa153), and their components and their structures were analyzed. Protein expression and variability in the antigenic specificity of fimbrillins were compared using Coomassie staining and western blotting using polyclonal antibodies against Mfa170A, Mfa170B, and Mfa153 proteins. Cell surface expression levels of fimbriae were analyzed by filtration enzyme-linked immunosorbent assays.

Results

The composition and structures of the purified Mfa1 fimbriae of 1439 was similar to that of JI-1. However, each Mfa1 protein of differential subtype/genotype was specifically detected by western blotting. Mfa170B fimbriae were expressed in several strains such as 1439, JKG9, B42, 1436, and Kyudai-3. Differential protein expression and antigenic heterogeneities were detected in Mfa2-5 between strains.

Conclusion

Mfa1 fimbriae from the mfa170A and mfa170B genotypes indicated an antigenic difference suggesting the mfa170B, is to be utilized for the novel classification of P. gingivalis.

Porphyromonas gulae and PPAD antibodies are not related to citrullination in rheumatoid arthritis

INTRODUCTION

Porphyromonas gulae have the enzyme PPAD, as P. gingivalis, which is responsible for citrullination related to the pathophysiology of rheumatoid arthritis and periodontitis; this implies the presence of two species of PPAD-producing bacteria in the mouth as well as the presence of citrullinated proteins. There are no previous reports or studies investigating an association between P. gulae PPAD in rheumatoid arthritis (RA).

OBJECTIVE

To assess the presence of P. gulae and anti-citrullinated peptide antibodies of P. gulae PAD in patients with RA and their possible relationship with clinical activity markers.

SUBJECTS AND METHODS

A total of 95 patients with RA and 95 controls were included. Erythrocyte sedimentation rate (ESR), C-reactive protein, anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) were measured. Activity index-28 (DAS28) and SCDAI. The periodontal diagnosis was established. Presence of P. gulae and P. gingivalis. An ELISA was used to determine antibodies against citrullinated peptides of P. gulae PAD.

RESULTS

A P. gulae frequency of 15.8% was observed in the RA group and 9.5% in the control group. Higher levels of ACPA were found in the P. gulae-positive patients of the RA group, finding no significant difference, but if in patients positive for P. gingivalis with statistical significance (p = 0.0001). The frequency of anti-VDK-cit and anti-LPQ-cit9 antibodies to PPAD of P. gulae was higher in the RA group than in the control group without significant difference. No relationship was found with the clinical variables despite the presence of P. gulae and anti-citrullinated peptide antibodies of P. gulae PPAD in patients with RA CONCLUSIONS: It was not possible to establish a connection with clinical variables in RA and P. gulae; as a result, the presence of P. gingivalis continues to contribute significantly to the increase in antibodies against citrullinated proteins/peptides from exogenous sources of citrullination in RA and periodontitis.

Prevalence of Periodontal Pathogens in Slovak Patients with Periodontitis and Their Possible Aspect of Transmission from Companion Animals to Humans

Oral health and diseases are greatly influenced by oral bacteria. During dysbiosis, bacterial composition changes, which can lead to periodontitis. Periodontitis in humans is associated with periodontal pathogens such as Treponema denticola, Porphyromonas gingivalis, Tannerella forsythia and Aggregatibacter actinomycetemcomitans. Animal-to-human transmission of some of these pathogens has also been reported. The aim of this study was to evaluate the prevalence of periodontal pathogens in Slovak patients and to assess the possible risk of transmission of these pathogens from animals to their owners. The presence of periodontal pathogens in dental plaque was monitored by PCR. Amplified products were analysed using Sanger sequencing. T. forsythia isolates were assessed for the susceptibility to different antibiotics using the disk diffusion method. In humans, T. denticola, P. gingivalis, T. forsythia and A. actinomycetemcomitans were present in 69.23%, 69.23%, 100% and 84.62%, respectively. Most isolates of T. forsythia were susceptible to amoxicillin-clavulanic acid, clindamycin and moxifloxacin, but they were resistant to metronidazole. The transmission of T. forsythia from animals to their owners was not proven based on sequence analysing. On the other hand, transmission of Porphyromonas gulae was confirmed, but the risk of its involvement in the pathogenesis of periodontitis in humans must be further investigated.

Porphyromonas gingivalis FimA and Mfa1 fimbriae: Current insights on localization, function, biogenesis, and genotype

In general, the periodontal pathogen Porphyromonas gingivalis expresses distinct FimA and Mfa1 fimbriae. Each of these consists of five FimA–E and five Mfa1–5 proteins encoded by the fim and mfa gene clusters, respectively. The main shaft portion comprises FimA and Mfa1, whereas FimB and Mfa2 are localized on the basal portion and function as anchors and elongation terminators. FimC–E and Mfa3–5 participate in the assembly of an accessory protein complex on the tips of each fimbria. Hence, they serve as ligands for the receptors on host cells and other oral bacterial species. The crystal structures of FimA and Mfa1 fimbrial proteins were recently elucidated and new insights into the localization, function, and biogenesis of these proteins have been reported. Several studies indicated a correlation between P. gingivalis pathogenicity and the fimA genotype but not the mfa1 genotype. We recently revealed polymorphisms of all genes in the fim and mfa gene clusters. Intriguingly, mfa5 occurred in numerous different forms and underwent duplication. Detailed structural and functional knowledge of the fimbrial proteins in the context of the entire filament could facilitate the development of innovative therapeutic strategies for structure-based drug design.

Diversity analysis of genes encoding Mfa1 fimbrial components in Porphyromonas gingivalis strains

Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is associated with the development of periodontal disease. The genetic diversity in virulence factors, such as adhesive fimbriae, among its strains affects the bacterial pathogenicity. P. gingivalis generally expresses two distinct types of fimbriae, FimA and Mfa1. Although the genetic diversity of fimA, encoding the major FimA fimbrilin protein, has been characterized, the genes encoding the Mfa1 fimbrial components, including the Mfa1 to Mfa5 proteins, have not been fully studied. We, therefore, analyzed their genotypes in 12 uncharacterized and 62 known strains of P. gingivalis (74 strains in total). The mfa1 genotype was primarily classified into two genotypes, 53 and 70. Additionally, we found that genotype 70 could be further divided into two subtypes (70A and 70B). The diversity of mfa2 to mfa4 was consistent with the mfa1 genotype, although no subtype in genotype 70 was observed. Protein structure modeling showed high homology between the genotypes in Mfa1 to Mfa4. The mfa5 gene was classified into five genotypes (A to E) independent of other genotypes. Moreover, genotype A was further divided into two subtypes (A1 and A2). Surprisingly, some strains had two mfa5 genes, and the 2^ndmfa5 exclusively occurred in genotype E. The Mfa5 protein in all genotypes showed a homologous C-terminal half, including the conserved C-terminal domain recognized by the type IX secretion system. Furthermore, the von Willebrand factor domain at the N-terminal was detected only in genotypes A to C. The mfa1 genotypes partially correlated with the ragA and ragB genotypes (located immediately downstream of the mfa gene cluster) but not with the fimA genotypes.