Manganese and iron homeostasis play an important role in oxidative stress protection in a variety of organisms. However, the transport and role of these metals in the periodontal pathogen Porphyromonas gingivalis were not well understood. Analysis of the genome of P. gingivalis W83 revealed the presence of two genes encoding homologs of ferrous iron transport protein, FeoB1 and FeoB2. The goal of this study was to determine the role of these two putative transporters in metal transport, their contributions to resistance to oxygen radicals and intracellular survival as well as the regulation and genetic organization of these two loci. Isogenic mutant strains deficient in FeoB1 and FeoB2, respectively, were generated and used in this study. The transport ability for manganese and iron was assessed and compared in feoB1, feoB2 mutant and wild type strains using 55Fe2+ and 54Mn2+. We demonstrated that feoB2 encodes a major manganese transporter, while FeoB1 functions as a major ferrous iron transporter. The roles of P. gingivalis FeoB1 and FeoB2 in oxidative stress defense and intracellular survival in host cells were determined using an oxidative stress survival assay and an in vitro infection assay, respectively. The feoB2 mutant exhibited reduced survival after exposure to H2O2 and to atmospheric oxygen and inside the host cells compared to the wild-type strain and its revertant, while the feoB1 mutant survived as well as the wild type strain under oxidative stress and possessed better capability to adhere to and survive in the host cells. Our results demonstrate that FeoB2 is required for protection of the bacterium from oxidative stress and for intracellular survival of P. gingivalis in host cells. However, FeoB1 is dispensable for both processes. Quantitative RT-PCR analysis revealed that expression of feoB2 in P. gingivalis is induced by oxidative stress. However, expression of feoB1 increased 2-fold upon exposure to lower growth temperature. Both observed inductions were specific and not detected under other stress conditions. We have also showed in this study that feoB2 is the second gene transcribed in an operon that is composed of a total of five genes and feoB1 is only co-transcribed with one downstream gene encoding a hypothetical protein. Notably, we also identified tandem repeats with potential to form stable stem-loop RNA secondary structure within the feoB2 and feoB1 transcripts.To our knowledge, this study has demonstrated the first connection among metal homeostasis, oxidative stress resistance and response to host cells in the periodontal pathogen, P. gingivalis.

Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is implicated as a major etiological agent in the initiation and progression of severe forms of periodontal disease. It has been reported that gingivitis and periodontal disease affect roughly 50.3% and 35% of the adult population, respectively. Therefore, approximately over 85% of the adult population may suffer from some form of gingival disease. Porphyromonas gingivalis, an established periodontopathogen, requires hemin for growth. Although multiple hemin uptake systems appear to be present in this organism, their specific role in hemin uptake and virulence remains unknown. Pigmentation is thought to result from the accumulation of iron protoporphyrin IX (FePPIX) derived from erythrocyte hemoglobin. It has been observed that mutations abolishing activity of the Lys-X specific cysteine protease, Kgp, resulted in loss of black pigmentation of P. gingivalis W83; they were less virulent than their wild-type counterparts. Thus, we have observed that Kgp degradation of fibrinogen deregulates the clotting cascade, thereby minimizing the availability of free erythrocytes. Additionally, Kgp binds erythrocytes and degrades them, releasing hemoglobin. The interference with mechanisms involved in the accumulation of black pigmentation may be significant in controlling the pathogenic potential of P. gingivalis. These results suggest that Lys-gingipain protease is a principal protein involved in acquisition of hemin from hemoglobin as well as a major factor in transport, by affecting the accumulation of FePPIX on the bacterial cell surface. Microarray analysis indicates a change in the expression of key enzymes and proteins required for hemin uptake, iron storage, electron transport and oxidative stress. Therefore, interference with mechanisms involved in accumulation of black pigmentation may be significant in controlling the pathogenic potential of P. gingivalis.

Porphyromonas gingivalis (P. gingivalis) is a gram-negative, anaerobic bacterium recognized as a major player in progression of periodontal disease. P. gingivalis survives in the oral cavity while being exposed to dynamic environmental conditions such as pH, temperature, nutrient availability and host immune responses such as oxygen tension and nitrosative stress. Survival and pathogenesis of P. gingivalis in the oral cavity require mechanisms to regulate gene expression in response to the extracellular signals. Little is known about the regulatory mechanisms of P. gingivalis in the oral cavity, so it is important to investigate and characterize these regulatory mechanisms. Adaptation to environmental cues using riboregulation is a significant mechanism for post-transcriptional regulation in bacteria. Using bioinformatics, we have identified a putative RNA-binding protein in P. gingivalis: RBP. Bioinformatic studies have led to the selection of HUβ and HUα nucleoid associated proteins as controls for RNA binding. I hypothesize that the candidate proteins RBP, HUβ and HUα bind RNA in P. gingivalis. The first aim is to show that RBP, HUβ and HUα bind RNA. Using electrophoretic mobility shift assays with IRE RNA and synthesized RNA motifs, I have confirmed that the proteins do bind RNA. The second aim is to isolate and sequence the P. gingivalis RNA that bind to RBP, HUβ and HUα. I have isolated the RNAs that bound the proteins and determined identity of the RNA using high throughput sequencing. Finally, I have identified an antibody that specifically binds RBP to use for in vivo immunoprecipitation of RNA-protein complexes from P. gingivalis. In conclusion RBP, HUβ and HUα are novel RNA binding proteins in P. gingivalis, and further investigation of these proteins is necessary to understand the mechanisms of gene regulation in P. gingivalis.

Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is a major etiological agent in the initiation and progression of severe forms of periodontal disease. Oral bacteria like P. gingivalis are subject to continually changing conditions as a consequence of host eating, oral hygiene patterns and subgingival temperatures. As such survival requires an adaptive response to environmental cues, but little is known about the mechanism by which P. gingivalis controls co- and post-transcriptional regulation of RNA levels and potentially protein expression. RNA-binding proteins (RBPs) are evolutionarily conserved across species and are involved in such regulatory mechanisms. However, P. gingivalis currently has no identified RBP. Recently, PG0627 has become an ideal candidate for a putative RBP due to its sequence homology to RBPs across various species. By characterizing PG0627, we can gain better insight into the function of this hypothetical protein and determine if it indeed behaves like an RNA-binding protein. A host of studies were done on a PG0627-deficient P. gingivalis mutant, V3139, in order to determine the biological role of the protein encoded by the gene. Our bioinformatics analysis indicated that PG0627 had sequence homology to several RNA recognition motifs or RBPs. Furthermore, our PG0627-deficient mutant, when compared to W83, exhibited decreased cell-associated iron content, decreased total interactions and invasions with eukaryotic cells, and decreased protease activity. Conversely, our PG0627-deficient mutant displayed slightly increased growth in the presence of nitrosative stress, and in hemin-depleted conditions. In conclusion, our results support that PG0627 is a valid candidate for an RNA-binding protein in P. gingivalis.

Porphorymonas gingivalis is one of the major bacterial pathogens responsible for the initiation and progression of periodontal disease. The bacterium requires hemin uptake for its growth and has developed sophisticated mechanisms to extract hemin from hemin containing proteins in the oral cavity. Hemin first binds to receptors on the surface of P. gingivalis and is then taken up in an energy dependent manner. TonB is an inner membrane bound protein that spans the periplasm and is believed to be involved in the passage of hemin through the double membrane of P. gingivalis. However, the TonB protein in P. gingivalis is yet to be identified. We identified PG0785 as a possible P. gingivalis TonB based on its bioinformatics data showing similarity to other known TonB proteins. We generated a P. gingivalis mutant lacking a functional PG0785 and then characterized the mutant to determine the role of PG0785. We performed metal content and protease assays, virulence studies and transcriptional and translational analysis of our mutant and wild type P. gingivalis strains. Phenotypic studies showed that the mutant cannot accumulate hemin on its surface. The mutant has significantly lower levels of iron compared to wild type based on metal content assays. The mutant also has significantly lower protease activity compared to the wild type. Virulence studies showed that the mutant interacted and invaded eukaryotic cells at much lower levels than the wild type. These results allowed us to speculate that PG0785 is very important in binding of hemin to surface of P. gingivalis. PG0785 also plays an important role in iron uptake, protease activity and virulence of P. gingivalis. Transcriptional and translational analyses have shown that numerous TonB related genes, metal uptake genes, hemin uptake genes and genes related to virulence have been differentially regulated in the mutant lacking a functional PG0785 gene compared to the wild type strain. In conclusion we believe that based on our results PG0785 is a putative P. gingivalis TonB protein that plays a significant role in the biology of P. gingivalis.

The facultative anaerobe, Escherichia coli and the obligate anaerobe, Porphyromonas gingivalis are two bacteria that reside in our body. Although they reside in separate environments, they are both subject to hydrogen peroxide stress and have mechanisms to regulate the stress. OxyR is the primary transcriptional regulator/sensor of oxidative stress response caused by hydrogen peroxide. OxyR in P. gingivalis is not well-characterized compared to OxyR in E. coli. We sought to characterize and compare the two forms of OxyR in order to gain a better understanding of the protein. We determined the oligomeric state of both proteins: primarily a tetramer for E. coli and primarily a tetramer for P. gingivalis OxyR.. We demonstrated DNA binding with E. coli OxyR, indicating purification of the functional form of E. coli OxyR.Through pulldown assays we discovered potential novel binding targets, mobB for E. coli OxyR and PG1209 for P. gingivalis OxyR. Many of the other targets corresponded to intergenic regions within genes, which may pertain to small RNAs or small proteins. These results show that OxyR in E. coli and P. gingivalis has novel function and properties indicating an expanded role in addition to the well-characterized oxidative stress response.

Porphyromonas gingivalis é um bacilo anaeróbio Gram negativo envolvido com o início e progressão de doenças periodontais. É considerado um colonizador tardio ou secundário do biofilme oral capaz de aderir a células de Streptococcus gordonii, um colonizador inicial do biofilme dental. Este estudo se propôs a comparar a expressão de genes de amostras de P. gingivalis isoladas de diferentes condições periodontais usando Differential Display (DD) Reverse Transcription PCR, durante a formação de biofilme misto com S. gordonii. O perfil de expressão gênica de células em biofilme (saúde e periodontite) foi comparado, assim como com células planctônicas pareadas. Bandas diferencialmente expressas nas diferentes condições foram clonadas e seqüenciadas, seguida de identificação dos genes em bancos de dados. A confirmação da expressão diferencial dos genes detectados foi realizada através de PCR em Tempo Real. Desses genes, alguns se relacionam com fatores de virulência, outros com obtenção de energia além de genes relacionados com proteínas de membrana e de transporte. / Porphyromonas gingivalis is a Gram negative anaerobic rod involved with the beginning and progression of periodontal diseases P. gingivalis is a late or secondary colonizer of oral biofilms and adhere to cells of Streptococcus gordonii, an early colonizer of dental plaque. This study aim to compare the gene expression of P. gingivalis strains isolated from different periodontal conditions using Differential Display (DD) Reverse Transcription PCR, in a mixed biofilm with S. gordonii. The gene expression profile was determined with biofilm cells (health and disease) and also with their planktonic samples partners. Bands differentially expressed were cloned, sequenciated and analyzed in gene data bank. Differential expression was confirmed by Real Time PCR. Some of the confirmed genes are related to virulence factors, energy metabolism and transport and membrane proteins.

Publicación a texto completo no autorizada por el autor / La realización del estudio tiene como objetivo el aislamiento de la bacteria Porphyromonas gingivalis, de pacientes con cuadros de periodontitis de la clínica estomatológica, perteneciente a la Facultad de Odontología de la Universidad Nacional Mayor de San Marcos, para luego enfrentarlas con la oleorresina de Copaifera reticulata “Copaiba”. Las muestras para la obtención del microorganismo, son tomadas con conos de papel N° 30 ó 40, colocados dentro del surco gingival a profundidad, por un tiempo de 60 segundos, luego se llevan al medio de transporte BHI (infusión cerebro corazón), diluidos en diferentes concentraciones y sembradas en el medio de agar sangre suplementado, incubándose en condiciones de anaerobiosis, a 37 °C durante 7 a 14 días. Para su identificación preliminar, se realizan pruebas de catalasa, oxidasa, y medios diferenciales como SIM, Urea, TSI (Tripe azúcar hierro) y Citrato. Para la identificación definitiva de la bacteria purificada, se realiza la prueba automatizada de Api 20 Anaerobios. El enfrentamiento se realiza por el test de difusión en agar con disco, para lo cual se prepara diez concentraciones distintas de la oleorresina, siendo el diluyente dimetilsulfoxido. Así mismo se prepara una suspensión equivalente al patrón 1 de Mc Farland de P. gingivalis, para ser sembrada, en un medio de agar sangre suplementado, luego se colocan los discos equidistantemente y se incuba a 37 °C durante siete a diez días en anaerobiosis. Los resultados de las mediciones de los halos de inhibición, dan una media en la Concentración Mínima Inhibitoria (CMI) de 3,4345 %. Se concluye que la oleorresina de copaiba, es un posible fitoproducto, que complementaria el tratamiento odontológico. / Tesis

Periodontal disease is a chronic inflammation of the gingiva and periodontium that leads to progressive destruction and irreversible damage to the supportive structures of the teeth. It affects nearly half of the United States population and is a particular risk factor in adults older than 65 years of age. Oral microorganisms assemble in plaque as a polymicrobial biofilm and Porphyromonas gingivalis, an important secondary colonizer in oral biofilms, has been implicated in periodontal disease. Although the protective functions of various salivary molecules such as antimicrobial proteins have been delineated, lipids present in saliva and on the oral mucosa have been largely ignored and there is growing evidence that the role of lipids in innate immunity is more important than previously realized. In fact, recent studies suggest that sphingoid bases and fatty acids, which exhibit potent broad spectrum antimicrobial activity against a variety of bacteria and fungi, are likely important innate immune molecules involved in the defense against oral bacterial and fungal infections. However little is known about their spectrum of activity or mechanisms of action. In addition, the effects of these lipids that are endogenous to the oral cavity have not been explored against oral bacteria. In this study I hypothesized that oral mucosal and salivary lipids exhibit dose-dependent antimicrobial activity against P. gingivalis and alter cell morphology and metabolic events. To test this hypothesis, I first examined the effects of two fatty acids: sapienic acid and lauric acid, and three sphingoid bases: sphingosine, dihydrosphingosine, and phytosphingosine, against a variety of gram-positive and gram-negative bacteria including P. gingivalis. Using broth microdilution assays to determine minimum inhibitory and minimum bactericidal concentrations, I show that antimicrobial activity against bacteria is dose-dependent, lipid specific, and microorganism specific. Kill kinetics were also variable across each bacteria-lipid combination. Upon examination of select bacteria-lipid combinations via scanning and transmission electron microscopy, different morphologies were evident across all treatments, demonstrating differential activity of each lipid for a particular bacterium as well as for each bacterium across different lipids. In addition, all sphingoid bases and fatty acids were taken up and retained in association with P. gingivalis cells and could be extracted along with bacterial lipids and separated using thin layer chromatography. Using a combination of two-dimensional in-gel electrophoresis and Western blots followed by mass spectroscopy and n-terminus degradation sequencing, I show that sapienic-acid treatment induces a unique stress response in P. gingivalis, as evidenced by the ability of P. gingivalis to upregulate a set of proteins involved in fatty acid biosynthesis metabolism and energy production, protein processing, cell adhesion, and virulence. Finally, utilizing flow cytometry and confocal microscopy, I assessed the effects of oral antimicrobial lipids against a representative host cell and describe oral lipid concentrations that are both antimicrobial to P. gingivalis cells and non-cytotoxic to the representative host cells tested. Combined, these data strongly suggest that sphingoid bases and fatty acids found within the saliva and on oral mucosa likely do contribute to the innate antimicrobial activity of saliva, mucosal surfaces, and skin and this dose-dependent activity is both lipid specific and bacteria specific. This information adds to current knowledge of the innate functions of endogenous lipids in the oral cavity. With bacterial resistance to current antibiotics increasing, the exploration of new antimicrobial agents is important and these lipid treatments may be beneficial for prophylactic treatments or therapeutic intervention of infection by supplementing the natural immune function of endogenous lipids on skin and other mucosal membranes.

Objectives: This investigation adapted the LIVE/DEAD� Baclight[TM] bacterial viability stain for the quantitative determination of bacterial cell viability of the aerotolerant anaerobes Porphyromonas gingivalis ATCC 33277 and Prevotella intermedia ATCC 25611. The Live/Dead stain was used to determine the influence of haem availability on the resistance of P. gingivalis and P. intermedia to the reactive oxygen species (ROS) superoxide anion and hydrogen peroxide and compare the sensitivities between the haem-requiring periodontal bacteria to ROS. Neutrophils use oxidative and non-oxidative killing mechanisms. During phagocytosis, neutrophils kill bacteria via a respiratory burst, producing ROS. P. gingivalis and P. intermedia are oxygen-tolerant gram-negative bacteria found in the gingival crevice. These bacteria express superoxide dismutase (SOD) activity, which extends some protection against superoxide radicals. Methods: Initially, experiments were performed to validate the reliability and accuracy of the fluorogenic Live/Dead stain using Escherichia coli ATCC 10798 (K-12), followed by experiments using P. gingivalis. The Live/Dead stain distinguishes viable:non-viable proportions of bacteria using mixtures of green (SYTO 9) and red (propidium iodide) fluorescent nucleic acid stains respectively. Bacterial cell viability was assessed with fluorescence microscopy and subsequently quantitative measurement using a fluorescence microplate reader (BMG Fluorostar plus Optima). P. gingivalis and P. intermedia colonies were subcultured from frozen cultures, in Tryptic soy broth (TSB) (Difco) and incubated anaerobically for approximately five days. They were further subcultured in pre-reduced TSB, supplemented with menadione 0.5[mu]g/ml (TSB-M) and either 5 [mu]g/ml haemin (Haem 5), 50 [mu]g/ml haemin (Haem 50) or without supplemental haemin (Haem 0). Cultures were grown anaerobically at 37�C to early stationary phase (approximately 48 hours). For experimental purposes, bacteria were harvested, washed and resuspended in 10 mM Tris-buffered saline (pH 7.5) containing peptone (TBS-P) (0.1 mg/ml), with a final adjustment to OD₅₄₀ [approximately equals] 2.0 (which corresponds to 1 x 10⁹ bacteria/ml). Bacterial suspensions were diluted ([approximately equals] 10⁸/ml) into TBS-P containing the fluorogenic viability stain (BacLight, Molecular Probes). Either pyrogallol (0.02 - 2 mM) or hydrogen peroxide (0.01 - 100 mM) was added (except to control tubes); tubes were vortexed for ten seconds and incubated at 37�C. Viability was monitored fluorimetrically for three hours. Results: For both P. gingivalis and P. intermedia, a pyrogallol concentration of 0.2 mM resulted in 80 to 90% cell death; and a hydrogen peroxide concentration of 10 mM killed approximately 80 to 90% of cells. Irrespective of the haem status, no significant difference was determined between the overall maximum rate of killing of P. gingivalis and P. intermedia, in their response to either superoxide or hydrogen peroxide; with the exception that the P. intermedia Haem 0 group was significantly less susceptible to hydrogen peroxide than the P. gingivalis Haem 0 group. For the majority of the experiments, there was no significant difference between final bacterial cell viability in the Haem 0 and Haem 5 cells for both species, after 3 hours exposure to various concentrations of ROS. However, the Haem 50 cells showed a significant increased susceptibility (albeit, a small difference) to both hydrogen peroxide and superoxide. Conclusions: The Live/Dead bacterial viability stain provided a valuable method to monitor "real-time" killing, avoiding the difficulties associated with culture-based methods for assessing viability. Haem availability had no clear influence on the resistance to ROS of either P. gingivalis or P. intermedia Haem 0 and Haem 5 cells. The Haem 50 cells showed a very slight increase in susceptibility to hydrogen peroxide and superoxide. Although P. intermedia may be isolated in significant numbers from healthy gingivae, as well as from periodontally diseased sites, it was no more resistant to ROS than was P. gingivalis, which is associated with periodontal lesions and difficult to cultivate from relatively healthy (more oxygenated) sites. This suggests that resistance to ROS does not contribute to the ecological distinction between these two species. The finding that haem availability did not influence sensitivity implies that these bacteria do not accumulate haem for the purpose of protection from ROS.