Comparative gene expression analysis of planktonic Porphyromonas gingivalis ATCC 33277 in the presence of a growing biofilm versus planktonic cells

How to study biofilms: technological advancements in clinical biofilm research

Biofilm formation is an important survival strategy commonly used by bacteria and fungi, which are embedded in a protective extracellular matrix of organic polymers. They are ubiquitous in nature, including humans and other animals, and they can be surface- and non-surface-associated, making them capable of growing in and on many different parts of the body. Biofilms are also complex, forming polymicrobial communities that are difficult to eradicate due to their unique growth dynamics, and clinical infections associated with biofilms are a huge burden in the healthcare setting, as they are often difficult to diagnose and to treat. Our understanding of biofilm formation and development is a fast-paced and important research focus. This review aims to describe the advancements in clinical biofilm research, including both in vitro and in vivo biofilm models, imaging techniques and techniques to analyse the biological functions of the biofilm.

A Novel Injectable Piezoelectric Hydrogel for Periodontal Disease Treatment

Periodontal disease is a multifactorial, bacterially induced inflammatory condition characterized by the progressive destruction of periodontal tissues. The successful nonsurgical treatment of periodontitis requires multifunctional technologies offering antibacterial therapies and promotion of bone regeneration simultaneously. For the first time, in this study, an injectable piezoelectric hydrogel (PiezoGEL) was developed after combining gelatin methacryloyl (GelMA) with biocompatible piezoelectric fillers of barium titanate (BTO) that produce electrical charges when stimulated by biomechanical vibrations (e.g., mastication, movements). We harnessed the benefits of hydrogels (injectable, light curable, conforms to pocket spaces, biocompatible) with the bioactive effects of piezoelectric charges. A thorough biomaterial characterization confirmed piezoelectric fillers' successful integration with the hydrogel, photopolymerizability, injectability for clinical use, and electrical charge generation to enable bioactive effects (antibacterial and bone tissue regeneration). PiezoGEL showed significant reductions in pathogenic biofilm biomass (∼41%), metabolic activity (∼75%), and the number of viable cells (∼2-3 log) compared to hydrogels without BTO fillers in vitro. Molecular analysis related the antibacterial effects to be associated with reduced cell adhesion (downregulation of porP and fimA) and increased oxidative stress (upregulation of oxyR) genes. Moreover, PiezoGEL significantly enhanced bone marrow stem cell (BMSC) viability and osteogenic differentiation by upregulating RUNX2, COL1A1, and ALP. In vivo, PiezoGEL effectively reduced periodontal inflammation and increased bone tissue regeneration compared to control groups in a mice model. Findings from this study suggest PiezoGEL to be a promising and novel therapeutic candidate for the treatment of periodontal disease nonsurgically.

Transcriptome analysis of Fusobacterium nucleatum reveals differential gene expression patterns in the biofilm versus planktonic cells

As a chronic infectious disease, periodontitis can cause gum recession, loss of alveolar bone, loosening of teeth, and even loss of teeth. Dental plaque biofilm is the initiating factor for the occurrence and development of periodontitis. Fusobacterium nucleatum (F. nucleatum) plays a vital role in the structure and ecology of dental plaque biofilms. It is a bridge between early and late colonization bacteria in dental plaque. Understanding the molecular mechanism of F. nucleatum during biofilm development is essential to control periodontitis. This study aimed to determine gene expression profiles of the F. nucleatum strain, ATCC 25586, in the planktonic and biofilm phase through RNA-sequencing approach. The results were confirmed by quantitative reverse transcriptase PCR (RT-qPCR). The results clearly illustrate the difference in gene expression of F. nucleatum under planktonic and biofilms. A total of 110 genes were differentially expressed by F. nucleatum in the biofilm state compared with the planktonic state. The 25 upregulated genes in the biofilm state were mainly related to carbohydrate and amino acid metabolism, while the 85 downregulated genes were primarily associated with cell growth, division, and oxidative stress; most of the upregulated genes of F. nucleatum involved in virulence and oral malodor. Furthermore, the transcriptome analysis and antibacterial activity test also identified Lysine might exhibit the antibacterial and antibiofilm activity of F. nucleatum for the first time. These new findings could provide caveats for future studies on the regulation and maintenance of plaque biofilm and the development of biomarkers for periodontitis.

Anti-Planktonic and Anti-Biofilm Properties of Pentacyclic Triterpenes-Asiatic Acid and Ursolic Acid as Promising Antibacterial Future Pharmaceuticals

Due to the ever-increasing number of multidrug-resistant bacteria, research concerning plant-derived compounds with antimicrobial mechanisms of action has been conducted. Pentacyclic triterpenes, which have a broad spectrum of medicinal properties, are one of such groups. Asiatic acid (AA) and ursolic acid (UA), which belong to this group, exhibit diverse biological activities that include antioxidant, anti-inflammatory, diuretic, and immunostimulatory. Some of these articles usually contain only a short section describing the antibacterial effects of AA or UA. Therefore, our review article aims to provide the reader with a broader understanding of the activity of these acids against pathogenic bacteria. The bacteria in the human body can live in the planktonic form and create a biofilm structure. Therefore, we found it valuable to present the action of AA and UA on both planktonic and biofilm cultures. The article also presents mechanisms of the biological activity of these substances against microorganisms.

Salmonella enterica serovar Enteritidis biofilm lifestyle induces lower pathogenicity and reduces inflammatory response in a murine model compared to planktonic bacteria

Salmonellaenterica serovar Enteritidis (S. Enteritidis) is the most frequent serovar involved in human salmonellosis. It has been demonstrated that about 80% of infections are related to biofilm formation. There is scant information about the pathogenicity of S. Enteritidis and its relationship to biofilm production. In this regard, this study aimed to investigate the differential host response induced by S. Enteritidis biofilm and planktonic lifestyle. To this purpose, biofilm and planktonic bacteria were inoculated to BALB/c mice and epithelial cell culture. Survival studies revealed that biofilm is less virulent than planktonic cells. Reduced signs of intestinal inflammation and lower bacterial translocation were observed in animals inoculated with Salmonella biofilm compared to the planktonic group. Results showed that Salmonella biofilm was impaired for invasion of non-phagocytic cells and induces a lower inflammatory response in vivo and in vitro compared to that of planktonic bacteria. Taken together, the outcome of Salmonella-host interaction varies depending on the bacterial lifestyle.

Gene Sets and Mechanisms of Sulfate-Reducing Bacteria Biofilm Formation and Quorum Sensing With Impact on Corrosion

Sulfate-reducing bacteria (SRB) have a unique ability to respire under anaerobic conditions using sulfate as a terminal electron acceptor, reducing it to hydrogen sulfide. SRB thrives in many natural environments (freshwater sediments and salty marshes), deep subsurface environments (oil wells and hydrothermal vents), and processing facilities in an industrial setting. Owing to their ability to alter the physicochemical properties of underlying metals, SRB can induce fouling, corrosion, and pipeline clogging challenges. Indigenous SRB causes oil souring and associated product loss and, subsequently, the abandonment of impacted oil wells. The sessile cells in biofilms are 1,000 times more resistant to biocides and induce 100-fold greater corrosion than their planktonic counterparts. To effectively combat the challenges posed by SRB, it is essential to understand their molecular mechanisms of biofilm formation and corrosion. Here, we examine the critical genes involved in biofilm formation and microbiologically influenced corrosion and categorize them into various functional categories. The current effort also discusses chemical and biological methods for controlling the SRB biofilms. Finally, we highlight the importance of surface engineering approaches for controlling biofilm formation on underlying metal surfaces.

Relevance of Biofilm Models in Periodontal Research: From Static to Dynamic Systems

Microbial biofilm modeling has improved in sophistication and scope, although only a limited number of standardized protocols are available. This review presents an example of a biofilm model, along with its evolution and application in studying periodontal and peri-implant diseases. In 2011, the ETEP (Etiology and Therapy of Periodontal and Peri-Implant Diseases) research group at the University Complutense of Madrid developed an in vitro biofilm static model using representative bacteria from the subgingival microbiota, demonstrating a pattern of bacterial colonization and maturation similar to in vivo subgingival biofilms. When the model and its methodology were standardized, the ETEP research group employed the validated in vitro biofilm model for testing in different applications. The evolution of this model is described in this manuscript, from the mere observation of biofilm growth and maturation on static models on hydroxyapatite or titanium discs, to the evaluation of the impact of dental implant surface composition and micro-structure using the dynamic biofilm model. This evolution was based on reproducing the ideal microenvironmental conditions for bacterial growth within a bioreactor and reaching the target surfaces using the fluid dynamics mimicking the salivary flow. The development of this relevant biofilm model has become a powerful tool to study the essential processes that regulate the formation and maturation of these important microbial communities, as well as their behavior when exposed to different antimicrobial compounds.

Inflammasome dysregulation in human gingival fibroblasts in response to periodontal pathogens

OBJECTIVE

Uncontrolled production of Interleukin-1β (IL-1β), a major proinflammatory cytokine, is associated with tissue destruction in periodontal disease. IL-1β production is controlled by inflammasomes which are multiprotein regulatory complexes. The current study aimed to elucidate potential regulatory pathways by monitoring the effects of periodontal pathogens Fusobacterium nucleatum (Fn) and Porphyromonas gingivalis (Pg) on inflammasomes and their regulators in human gingival fibroblasts (HGFs) in vitro.

METHODS

HGFs were exposed to Fn and Pg alone or in combination for 24 hr at a multiplicity of infection of 100, ±30 min exposure with 5 mM adenosine triphosphate (ATP) incubation. Gene expression of NLRP3 and AIM2, inflammasome regulatory proteins POP1, CARD16 and TRIM16, and inflammasome components ASC and CASPASE 1, and IL-1β, were evaluated by RT-PCR. Pro- and mature IL-1β levels were monitored intracellularly by immunocytochemistry and extracellularly by ELISA.

RESULTS

Fn + ATP significantly upregulated NLRP3, AIM2, IL-1β, ASC, and CASPASE 1; however, it downregulated POP1 and TRIM16. Pg + ATP downregulated NLRP3, ASC, POP1, but upregulated IL-1β and CARD16. Pg + Fn+ATP significantly upregulated AIM2, IL-1β and CARD16, and downregulated POP1, TRIM16, and CASPASE 1. Pg + ATP exposure significantly increased pro- and mature IL-1β production.

CONCLUSION

Bacterial exposure with ATP may deregulate IL-1β by dysregulating inflammasomes and their regulators in HGFs.

Antimicrobial Activity of EPA and DHA against Oral Pathogenic Bacteria Using an In Vitro Multi-Species Subgingival Biofilm Model

In search for natural products with antimicrobial properties for use in the prevention and treatment of periodontitis, the purpose of this investigation was to evaluate the antimicrobial activity of two omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), using an in vitro multi-species subgingival biofilm model including Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans. The antimicrobial activities of EPA and DHA extracts (100 µM) and the respective controls were assessed on 72 h biofilms by their submersion onto discs for 60 s. Antimicrobial activity was evaluated by quantitative polymerase chain reaction (qPCR), confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). ANOVA with Bonferroni correction was used to evaluate the antimicrobial activity of each of the fatty acids. Both DHA and EPA significantly reduced (p < 0.001 in all cases) the bacterial strains used in this biofilm model. The results with CLSM were consistent with those reported with qPCR. Structural damage was evidenced by SEM in some of the observed bacteria. It was concluded that both DHA and EPA have significant antimicrobial activity against the six bacterial species included in this biofilm model.

Specific Anti-biofilm Activity of Carbon Quantum Dots by Destroying P. gingivalis Biofilm Related Genes

Introduction

Biofilms protect bacteria from antibiotics and this can produce drug-resistant strains, especially the main pathogen of periodontitis, Porphyromonas gingivalis. Carbon quantum dots with various biomedical properties are considered to have great application potential in antibacterial and anti-biofilm treatment.

Methods

Tinidazole carbon quantum dots (TCDs) and metronidazole carbon quantum dots (MCDs) were prepared by a hydrothermal method with the clinical antibacterial drugs tinidazole and metronidazole, respectively. Then, TCDs and MCDs were characterized by transmission electron microscopy, UV–visible spectroscopy, infrared spectroscopy and energy-dispersive spectrometry. The antibacterial effects were also investigated under different conditions.

Results

The TCDs and MCDs had uniform sizes. The results of UV–visible and energy-dispersive spectrometry confirmed their important carbon polymerization structures and the activity of the nitro group, which had an evident inhibitory effect on P. gingivalis, but almost no effect on other bacteria, including Escherichia coli, Staphylococcus aureus and Prevotella nigrescens. Importantly, the TCDs could penetrate the biofilms to further effectively inhibit the growth of P. gingivalis under the biofilms. Furthermore, it was found that the antibacterial effect of TCDs lies in its ability to impair toxicity by inhibiting the major virulence factors and related genes involved in the biofilm formation of P. gingivalis, thus affecting the self-assembly of biofilm-related proteins.

Conclusion

The findings demonstrate a promising new method for improving the efficiency of periodontitis treatment by penetrating the P. gingivalis biofilm with preparations of nano-level antibacterial drugs.

Effects of Porphyromonas gingivalis and Fusobacterium nucleatum on inflammasomes and their regulators in H400 cells

INTRODUCTION

Inflammasomes are multiprotein complexes that regulate immune processes in response to infections and tissue damage. They modulate Interleukin-1beta (IL-1β) expression, a major proinflammatory cytokine. The inflammasome/IL-1β pathway is involved in head and neck squamous cell carcinoma (HNSCC) progression and the periodontal pathogens Fusobacterium nucleatum (Fn) and Porphyromonas gingivalis (Pg) have been reported to cause chronic inflammation in HNSCC. The aim of this study was to characterise the role of these pathogens in regulating inflammasome activity and the IL-1β response in HNSCC in vitro.

METHODS

An HNSCC cell line (H400) was exposed to Fn and Pg individually or in combination for 24h, ± incubation for 30 min with 5 mM adenosine triphosphate (ATP). Transcript levels of inflammasomes, NLRP3 and AIM2; inflammasome-regulatory proteins, POP1, CARD16 and TRIM16; and inflammasome-component, ASC and caspase 1 and IL-1β, were assayed by RT-PCR. Expression of IL-1β was by immunocytochemistry and ELISA.

RESULTS

NLRP3 expression was significantly upregulated in response to Pg, Fn + Pg, Pg + ATP and Fn + Pg + ATP. AIM2 was significantly upregulated by Fn, Pg and Fn + Pg + ATP exposure. All conditions significantly upregulated IL-1β gene expression. POP1 expression was significantly downregulated by Pg or Fn exposure but not by Fn + Pg. Intracellular pro- and mature IL-1β were significantly higher following Fn and Pg + ATP exposure.

CONCLUSION

Pg alone increased IL-1β by upregulating AIM2, NLRP3 and downregulating POP1. Fn promoted IL-1β by increasing AIM2 and downregulating POP1. Pg + ATP with or without Fn upregulated NLRP3, IL-1β by downregulating POP1. Periodontal pathogens may contribute to HNSCC pathogenesis by increasing the IL-1β response due to inflammasome dysregulation.

Optimization of ZnO Nanorods Growth on Polyetheresulfone Electrospun Mats to Promote Antibacterial Properties

Zinc oxide (ZnO) nanorods grown by chemical bath deposition (CBD) on the surface of polyetheresulfone (PES) electrospun fibers confer antimicrobial properties to the obtained hybrid inorganic–polymeric PES/ZnO mats. In particular, a decrement of bacteria colony forming units (CFU) is observed for both negative (Escherichia coli) and positive (Staphylococcus aureus and Staphylococcus epidermidis) Grams. Since antimicrobial action is strictly related to the quantity of ZnO present on surface, a CBD process optimization is performed to achieve the best results in terms of coverage uniformity and reproducibility. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) provide morphological and compositional analysis of PES/ZnO mats while thermogravimetric analysis (TGA) is useful to assess the best process conditions to guarantee the higher amount of ZnO with respect to PES scaffold. Biocidal action is associated to Zn²⁺ ion leaching in solution, easily indicated by UV–Vis measurement of metallation of free porphyrin layers deposited on glass.

Gene expression of Porphyromonas gingivalis ATCC 33277 when growing in an in vitro multispecies biofilm

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis, an oral microorganism residing in the subgingival biofilm, may exert diverse pathogenicity depending on the presence of specific virulence factors, but its gene expression has not been completely established. This investigation aims to compare the transcriptomic profile of this pathogen when growing within an in vitro multispecies biofilm or in a planktonic state.

MATERIALS AND METHODS

P. gingivalis ATCC 33277 was grown in anaerobiosis within multi-well culture plates at 37°C under two conditions: (a) planktonic samples (no hydroxyapatite discs) or (b) within a multispecies-biofilm containing Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans deposited on hydroxyapatite discs. Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) combined with Fluorescence In Situ Hybridization (FISH) were used to verify the formation of the biofilm and the presence of P. gingivalis. Total RNA was extracted from both the multispecies biofilm and planktonic samples, then purified and, with the use of a microarray, its differential gene expression was analyzed. A linear model was used for determining the differentially expressed genes using a filtering criterion of two-fold change (up or down) and a significance p-value of <0.05. Differential expression was confirmed by Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR).

RESULTS

SEM verified the development of the multispecies biofilm and FISH confirmed the incorporation of P. gingivalis. The microarray demonstrated that, when growing within the multispecies biofilm, 19.1% of P. gingivalis genes were significantly and differentially expressed (165 genes were up-regulated and 200 down-regulated), compared with planktonic growth. These genes were mainly involved in functions related to the oxidative stress, cell envelope, transposons and metabolism. The results of the microarray were confirmed by RT-qPCR.

CONCLUSION

Significant transcriptional changes occurred in P. gingivalis when growing in a multispecies biofilm compared to planktonic state.