Episymbiotic Saccharibacteria suppresses gingival inflammation and bone loss in mice through host bacterial modulation.

Saccharibacteria (TM7) are obligate epibionts living on the surface of their host bacteria and are strongly correlated with dysbiotic microbiomes during periodontitis and other inflammatory diseases, suggesting they are putative pathogens. However, due to the recalcitrance of TM7 cultivation, causal research to investigate their role in inflammatory diseases is lacking. Here, we isolated multiple TM7 species on their host bacteria from periodontitis patients. These TM7 species reduce inflammation and consequential bone loss by modulating host bacterial pathogenicity in a mouse ligature-induced periodontitis model. Two host bacterial functions involved in collagen binding and utilization of eukaryotic sialic acid are required for inducing bone loss and are altered by TM7 association. This TM7-mediated downregulation of host bacterial pathogenicity is shown for multiple TM7/host bacteria pairs, suggesting that, in contrast to their suspected pathogenic role, TM7 could protect mammalian hosts from inflammatory damage induced by their host bacteria.

Antibiofilm effects of Thymus vulgaris and Hyptis spicigera essential oils on cariogenic bacteria.

Aim: The inhibitory and antibiofilm effects of Thymus vulgaris (EOTv) and Hyptis spicigera essential oils (EOHs) on cariogenic microorganisms were evaluated. Materials & methods: The chemical characterization of EOTv was performed by gas chromatography/mass spectrometry. Streptococcus mutans, Streptococcus gordonii, Streptococcus sanguinis, Streptococcus mitis, Streptococcus sobrinus, Lactobacillus acidophilus and Actinomyces naeslundii were used for agar diffusion assays and determination of minimal inhibitory and minimal bactericide concentrations. In addition, 20 streptococci and lactobacilli clinical isolates were also tested. The effects of essential oil on microbial initial biofilm formation and on preformed microcosm biofilm formed from human saliva were studied. Results & conclusion: Both essential oils had inhibitory effects on the cariogenic species and reduced the bacterial adherence to dental enamel. Essential oils were able to disrupt preformed microcosm biofilms. Thymus vulgaris and Hyptis spicigera essential oils have potential to be used in the development of formulations to the control of cariogenic biofilms.

Short chain fatty acids induced the type 1 and type 2 fimbrillin-dependent and fimbrillin-independent initial attachment and colonization of Actinomyces oris monoculture but not coculture with streptococci.

BACKGROUND: Actinomyces oris is an early colonizer and has two types of fimbriae on its cell surface, type 1 fimbriae (FimP and FimQ) and type 2 fimbriae (FimA and FimB), which contribute to the attachment and coaggregation with other bacteria and the formation of biofilm on the tooth surface, respectively. Short-chain fatty acids (SCFAs) are metabolic products of oral bacteria including A. oris and regulate pH in dental plaques. To clarify the relationship between SCFAs and fimbrillins, effects of SCFAs on the initial attachment and colonization (INAC) assay using A. oris wild type and fimbriae mutants was investigated. INAC assays using A. oris MG1 strain cells were performed with SCFAs (acetic, butyric, propionic, valeric and lactic acids) or a mixture of them on human saliva-coated 6-well plates incubated in TSB with 0.25% sucrose for 1 h. The INAC was assessed by staining live and dead cells that were visualized with a confocal microscope. RESULTS: Among the SCFAs, acetic, butyric and propionic acids and a mixture of acetic, butyric and propionic acids induced the type 1 and type 2 fimbriae-dependent and independent INAC by live A. oris, but these cells did not interact with streptococci. The main effects might be dependent on the levels of the non-ionized acid forms of the SCFAs in acidic stress conditions. GroEL was also found to be a contributor to the FimA-independent INAC by live A. oris cells stimulated with non-ionized acid. CONCLUSION: SCFAs affect the INAC-associated activities of the A. oris fimbrillins and non-fimbrillins during ionized and non-ionized acid formations in the form of co-culturing with other bacteria in the dental plaque but not impact the interaction of A. oris with streptococci.

Bacteria Residing at Root Canals Can Induce Cell Proliferation and Alter the Mechanical Properties of Gingival and Cancer Cells.

Understanding the importance of oral microbiota in human health and disease also leads to an expansion of the knowledge on functional, metabolic, and molecular alterations directly contributing to oral and systemic pathologies. To date, a compelling number of studies have documented the crucial role of some oral cavity-occurring microbes in the initiation and progression of cancers. Although this effect was noted primarily for Fusobacterium spp., the potential impact of other oral microbes is also worthy of investigation. In this study, we aimed to assess the effect of Enterococcus faecalis, Actinomyces odontolyticus, and Propionibacterium acnes on the proliferation capability and mechanical features of gingival cells and cell lines derived from lung, breast, and ovarian cancers. For this purpose, we incubated selected cell lines with heat-inactivated bacteria and supernatants collected from biofilms, cultured in both anaerobic and aerobic conditions, in the presence of surgically removed teeth and human saliva. The effect of oral bacteria on cell population growth is variable, with the highest growth-promoting abilities observed for E. faecalis in relation to human primary gingival fibroblasts (HGF) and lung cancer A549 cells, and P. acnes in relation to breast cancer MCF-7 and ovarian cancer SKOV-3 cells. Notably, this effect seems to depend on a delicate balance between the pro-stimulatory and toxic effects of bacterial-derived products. Regardless of the diverse effect of bacterial products on cellular proliferation capability, we observed significant alterations in stiffness of gingival and lung cancer cells stimulated with E. faecalis bacteria and corresponding biofilm supernatants, suggesting a novel molecular mechanism involved in the pathogenesis of diseases in oral cavities and tooth tissues. Accordingly, it is proposed that analysis of cancerogenic features of oral cavity bacteria should be multivariable and should include investigation of potential alterations in cell mechanical properties. These findings corroborate the important role of oral hygiene and root canal treatment to assure the healthy stage of oral microbiota.

Effect of thymoquinone on Fusobacterium nucleatum­associated biofilm and inflammation.

Periodontitis affects oral tissues and induces systemic inflammation, which increases the risk of cardiovascular disease and metabolic syndrome. Subgingival plaque accumulation is a trigger of periodontitis. Fusobacterium nucleatum (FN) contributes to subgingival biofilm complexity by intercalating with early and late bacterial colonizers on tooth surfaces. In addition, inflammatory responses to FN are associated with the progression of periodontitis. Nigella sativa Lin. seed, which is known as black cumin (BC), has been used as a herbal medicine to treat ailments such as asthma and infectious diseases. The current study examined the inhibitory effect of BC oil and its active constituents, thymol (TM) and thymoquinone (TQ), on FN­associated biofilm and inflammation. FN­containing biofilms were prepared by co­cultivation with an early dental colonizer, Actinomyces naeslundii (AN). The stability and biomass of FN/AN dual species biofilms were significantly higher compared with FN alone. This effect was retained even with prefixed cells, indicating that FN/AN co­aggregation is mediated by physicochemical interactions with cell surface molecules. FN/AN biofilm formation was significantly inhibited by 0.1% TM or TQ. Confocal laser scanning microscopy indicated that treatment of preformed FN/AN biofilm with 0.01% of BC, TM or TQ significantly reduced biofilm thickness, and TQ demonstrated a cleansing effect equivalent to that of isopropyl methylphenol. TQ dose­dependently suppressed TNF­α production from a human monocytic cell line, THP­1 exposed to FN, yet showed no toxicity to THP­1 cells. These results indicated that oral hygiene care using TQ could reduce FN­associated biofilm and inflammation in gingival tissue.

Streptococcus mutans adhesion force sensing in multi-species oral biofilms.

Bacteria utilize chemical and mechanical mechanisms to sense their environment, to survive hostile conditions. In mechanical sensing, intra-bilayer pressure profiles change due to deformation induced by the adhesion forces bacteria experience on a surface. Emergent properties in mono-species Streptococcus mutans biofilms, such as extracellular matrix production, depend on the adhesion forces that streptococci sense. Here we determined whether and how salivary-conditioning film (SCF) adsorption and the multi-species nature of oral biofilm influence adhesion force sensing and associated gene expression by S. mutans. Hereto, Streptococcus oralis, Actinomyces naeslundii, and S. mutans were grown together on different surfaces in the absence and presence of an adsorbed SCF. Atomic force microscopy and RT-qPCR were used to measure S. mutans adhesion forces and gene expressions. Upon SCF adsorption, stationary adhesion forces decreased on a hydrophobic and increased on a hydrophilic surface to around 8 nN. Optical coherence tomography showed that triple-species biofilms on SCF-coated surfaces with dead S. oralis adhered weakly and often detached as a contiguous sheet. Concurrently, S. mutans displayed no differential adhesion force sensing on SCF-coated surfaces in the triple-species biofilms with dead S. oralis, but once live S. oralis were present S. mutans adhesion force sensing and gene expression ranked similar as on surfaces in the absence of an adsorbed SCF. Concluding, live S. oralis may enzymatically degrade SCF components to facilitate direct contact of biofilm inhabitants with surfaces and allow S. mutans adhesion force sensing of underlying surfaces to define its appropriate adaptive response. This represents a new function of initial colonizers in multi-species oral biofilms.

A rare case of brain abscess caused by Actinomyces meyeri.

BACKGROUND: Brain abscesses are the rare and most severe form of actinomycosis, which usually manifests as abscesses of the occipital or parietal lobe due to direct expansion from an adjacent area, the oral cavity. In the medical literature, there are only a few reported cases of brain abscess caused by Actinomyces meyeri. In this report, we present a 35-year-old male patient who experienced an insidious headache and left-sided weakness and was diagnosed with an Actinomyces meyeri brain abscess. CASE PRESENTATION: A 35-year-old Nepalese man came to our institute with the primary complaint of insidious onset of headache and left-sided weakness. His physical examination was remarkable for the left-sided weakness with power 2/5 on both upper and lower limbs, hypertonia, hyperreflexia and positive Babinski sign, with intact sensory function. Cardiac examination revealed systolic murmur with regular S1 and S2, and lung examination was normal. The patient had poor dental hygiene. Biochemistry and haematology panel were normal. Urinalysis, chest X-ray and electrocardiogram revealed no abnormality. A transthoracic echocardiogram revealed mitral regurgitation. However, there was no evidence of valvular vegetation. A magnetic resonance imaging (MRI) of the brain was performed, which showed a bi-lobed rim enhancing lesion with a conglomeration of two adjoining round lesions in the right parietal parasagittal region. Perilesional oedema resulting in mass effect over the right lateral ventricle and mid-right uncal herniation with midline shift was noted. Craniotomy was performed, and the lesion was excised. Gram staining of the extracted sample revealed gram variable filamentous rods. Creamy white, moist, confluent colonies were observed after performing anaerobic culture in chocolate agar. On the gram staining, they showed gram-positive filamentous rods. Actinomyces meyeri was identified based on matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) technology. Based on the susceptibilities, he was successfully treated with ampicillin-sulbactam. CONCLUSIONS: In conclusion, Actinomyces should be considered in the differential diagnosis of brain abscess in patients with poor dental hygiene, and early diagnosis and appropriate treatment can lead to better results.

Early host-microbe interaction in a peri-implant oral mucosa-biofilm model.

The host-microbe relationship is pivotal for oral health as well as for peri-implant diseases. Peri-implant mucosa and commensal biofilm play important roles in the maintenance of host-microbe homeostasis, but little is known about how they interact. We have therefore investigated the early host-microbe interaction between commensal multispecies biofilm (Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar, Porphyromonas gingivalis) and organotypic peri-implant mucosa using our three-dimensional model. After 24 hr, biofilms induced weak inflammatory reaction in the peri-implant mucosa by upregulation of five genes related to immune response and increased secretion of IL-6 and CCL20. Biofilm volume was reduced which might be explained by secretion of ß-Defensins-1, -2, and CCL20. The specific tissue reaction without intrinsic overreaction might contribute to intact mucosa. Thus, a relationship similar to homeostasis and oral health was established within the first 24 hr. In contrast, the mucosa was damaged and the bacterial distribution was altered after 48 hr. These were accompanied by an enhanced immune response with upregulation of additional inflammatory-related genes and increased cytokine secretion. Thus, the homeostasis-like relationship was disrupted. Such profound knowledge of the host-microbe interaction at the peri-implant site may provide the basis to improve strategies for prevention and therapy of peri-implant diseases.

Orally administered pathobionts and commensals have comparable and innocuous systemic effects on germ-free mice.

BACKGROUND AND OBJECTIVES: Recent evidence suggests that oral bacteria can affect extra-oral diseases by modulating aspects of the gut environment such as the microbiome, metabolome, and immune profiles. However, differences in the effects of different types of oral bacteria, particularly periodontopathic and health-associated bacteria, remain elusive. MATERIALS AND METHODS: Five-week-old germ-free mice were orally administered with either periodontopathic bacteria as oral pathobionts (Porphyromonas gingivalis, Filifactor alocis, and Fusobacterium nucleatum) or bacteria associated with periodontal health (Actinomyces naeslundii, Streptococcus mitis, and Veillonella rogosae) twice a week for five weeks. The presence of all bacterial species in the feces and the livers of the mice was analyzed via polymerase chain reaction (PCR), using specific primers for 16S rRNA genes. Alveolar bone resorption was evaluated histologically. The expression profiles of various genes in the liver and small intestine were analyzed using real-time PCR. Sera were analyzed to determine the levels of antibodies and endotoxin. The proportions of T helper 17 (Th17) and regulatory T (Treg) cells in mesenteric lymph nodes and Peyer's patches were analyzed using flow cytometry. RESULTS: Neither of the types of bacteria administered in this experiment induced alveolar bone resorption. All bacteria elicited some degree of systemic antibody response in the mice, although the response to S. mitis was not obvious. The response to P. gingivalis and V. rogosae was strongest. Generally, the health-associated bacteria but not the periodontitis-associated bacteria were detected in fecal samples. Interestingly, only Fusobacterium nucleatum DNA was detected in the liver, despite that live Fusobacterium nucleatum were not detected in the liver. The levels of interleukin-17 in the intestine and genes related to lipid accumulation in the liver were significantly higher in the mice that received periodontitis-associated bacteria. In addition, expression of the gene associated with endoplasmic reticulum stress was higher and that of the gene controlling circadian rhythm was lower in the periodontitis group. There was no difference in serum endotoxin, T-cell phenotypes in the lymphatic tissues, or genes related to the gut barrier. CONCLUSION: Oral administration of periodontitis-associated bacteria can induce pathological changes in the liver and intestine that are implicated in the process of periodontitis. These findings further support the importance of the oral-gut connection.

Visible-Light-Induced Photocatalytic and Antibacterial Activity of TiO2 Codoped with Nitrogen and Bismuth: New Perspectives to Control Implant-Biofilm-Related Diseases.

Biofilm-associated diseases are one of the main causes of implant failure. Currently, the development of implant surface treatment goes beyond the osseointegration process and focuses on the creation of surfaces with antimicrobial action and with the possibility to be re-activated (i.e., light source activation). Titanium dioxide (TiO2), an excellent photocatalyst used for photocatalytic antibacterial applications, could be a great alternative, but its efficiency is limited to the ultraviolet (UV) range of the electromagnetic spectrum. Since UV radiation has carcinogenic potential, we created a functional TiO2 coating codoped with nitrogen and bismuth via the plasma electrolytic oxidation (PEO) of titanium to achieve an antibacterial effect under visible light with re-activation potential. A complex surface topography was demonstrated by scanning electron microscopy and three-dimensional confocal laser scanning microscopy. Additionally, PEO-treated surfaces showed greater hydrophilicity and albumin adsorption compared to control, untreated titanium. Bismuth incorporation shifted the band gap of TiO2 to the visible region and facilitated higher degradation of methyl orange (MO) in the dark, with a greater reduction in the concentration of MO after visible-light irradiation even after 72 h of aging. These results were consistent with the in vitro antibacterial effect, where samples with nitrogen and bismuth in their composition showed the greatest bacterial reduction after 24 h of dual-species biofilm formation ( Streptococcus sanguinis and Actinomyces naeslundii) in darkness with a superior effect at 30 min of visible-light irradiation. In addition, such a coating presents reusable photocatalytic potential and good biocompatibility by presenting a noncytotoxicity effect on human gingival fibroblast cells. Therefore, nitrogen and bismuth incorporation into TiO2 via PEO can be considered a promising alternative for dental implant application with antibacterial properties in darkness, with a stronger effect after visible-light application.

Lactobacillus plantarum Lipoteichoic Acid Inhibits Oral Multispecies Biofilm.

INTRODUCTION: Apical periodontitis is an inflammatory disease in the periradicular region of teeth that results from infection by multispecies bacterial biofilm residing in the root canal system. In this study, we investigated whether Lactobacillus plantarum lipoteichoic acid (Lp.LTA) could inhibit multispecies oral pathogenic bacterial biofilm formation. METHODS: Highly pure and structurally intact Lp.LTA was purified from L. plantarum. Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans, and Enterococcus faecalis were co-cultured to form oral multispecies biofilm in the presence or absence of Lp.LTA on culture plates or human dentin slices. Preformed biofilm was treated with or without Lp.LTA, followed by additional treatment with intracanal medicaments such as calcium hydroxide or chlorhexidine digluconate. Confocal microscopy and crystal violet assay were performed to determine biofilm formation. Biofilm on human dentin slices was visualized with a scanning electron microscope. RESULTS: Biofilm formation of multispecies bacteria on the culture dishes was dose-dependently reduced by Lp.LTA compared with the nontreatment control group. Lp.LTA also inhibited multispecies biofilm formation on the dentin slices in a dose-dependent manner. Interestingly, Lp.LTA was shown to reduce preformed multispecies biofilm compared with the nontreatment group. Moreover, Lp.LTA potentiated the effectiveness of the intracanal medicaments in the removal of preformed multispecies biofilm. CONCLUSIONS: These results suggest that Lp.LTA is a potential anti-biofilm agent for treatment or prevention of oral infectious disease, including apical periodontitis, which is mainly caused by multispecies bacterial biofilm.

Exploring the potential of actinomycetes in improving soil fertility and grain quality of economically important cereals.

The search for environment-friendly, economical and healthy alternatives to agrochemicals tempted us to evaluate the potential of naturally occurring actinomycetes to improve soil properties, plant growth and photosynthesis, grain yield and chemical composition of economically important cereals (wheat, barley, oat, maize and sorghum). To this end, actinomycetes were isolated from soils of local cereals fields, then their biological activities, namely antibacterial, antiprotozoal, antioxidant, and phenolic and flavonoid contents were evaluated. The four most active isolates (9, 16, 24 and 26) were selected and used for enriching the soils until seed set. Each isolate was separately applied. Seeds of the selected cereals were grown in the actinomycete-enriched soils. The soils were analyzed for their electrical conductivity, pH values, total phenolics, organic matter and mineral content. At the vegetative stage, chlorophyll content and gas exchange rates were measured. Mature seeds were then harvested, the yield was evaluated and the seeds were analyzed for their primary and secondary metabolites. The selected isolates improved the grain yield in all tested cereals and most noticeably in barley and maize as compared to control counterparts. These positive effects were probably a result of increased carbon gain due to higher chlorophyll and photosynthetic rate. Isolate 26 showed the highest effect on grains composition profiles followed by the isolate 16. Phenolics and sugars of all grains increased by treatment with the tested isolates. Isolate 26 was the most effective in this regard. All isolates generally improved vitamins, amino acids and organic acids contents in grains. However, fatty acids profile showed a decrease in the content of all measured fatty acids by isolate 26 and an increase in the contents by isolate 16. These results emphasize the potential of actinomycete enrichment as an alternative to agrochemicals and strongly suggest that they can be used in organic farming.

Monospecies and polymicrobial biofilms differentially regulate the phenotype of genotype-specific oral cancer cells.

Microbial infection has been shown to involve in oral carcinogenesis; however, the underlying mechanisms remain poorly understood. The present study aimed to characterize the growth of oral microorganisms as both monospecies and polymicrobial biofilms and determine the effects of their products on oral keratinocytes. Candida albicans (ALC3), Actinomyces naeslundii (AN) and Streptococcus mutans (SM) biofilms or a combination of these (TRI) were grown in flow-cell system for 24 h. The biofilms were subjected to fluorescent in situ hybridization using species-specific probes and analysed using confocal laser scanning microscopy. The effluent derived from each biofilm was collected and incubated with malignant (H357) and normal (OKF6) oral keratinocytes to assess extracellular matrix adhesion, epithelial-mesenchymal transition (EMT) and cytokines expression. Incubation of OKF6 with ALC3 and TRI effluent significantly decreased adhesion of the oral keratinocyte to collagen I, whereas incubation of H357 with similar effluent increased adhesion of the oral keratinocyte to laminin I, significantly when compared with incubation with artificial saliva containing serum-free medium (NE; P < 0.05). In OKF6, changes in E-cadherin and vimentin expression were not consistent with EMT although there was evidence of a mesenchymal to epithelial transition in malignant oral keratinocytes incubated with AN and SM effluent. A significant increase of pro-inflammatory cytokines expression, particularly interleukin (IL)-6 and IL-8, was observed when H357 was incubated with all biofilm effluents after 2- and 24-h incubation when compared with NE (P < 0.05). In conclusion, C.albicans, A.naeslundii and S.mutans form polymicrobial biofilms which differentially modulate malignant phenotype of oral keratinocytes.

REPEATED ANESTHESIA IN A BLACK RHINOCEROS ( DICEROS BICORNIS) TO MANAGE UPPER RESPIRATORY OBSTRUCTION.

This report describes weekly repeated anesthesia in a 7-yr-old, 1,030 kg, female Eastern black rhinoceros ( Diceros bicornis michaeli), that was immobilized six times using a combination of 2 mg etorphine (0.002 mg/kg), 5 mg medetomidine (0.005 mg/kg), 25 mg midazolam (0.024 mg/kg), and 300 mg ketamine (0.29 mg/kg) delivered intramuscularly (IM) via remote dart to facilitate long-term medical care of a bilateral, obstructive Actinomyces sp. rhinitis. The drug combination described in this study resulted in reliable, rapid recumbency of the animal within 2-8 min after initial administration via dart and produced deep anesthesia for 34-78 min without supplemental anesthetic administration. Antagonist drugs (100 mg naltrexone [0.1 mg/kg] and 25 mg atipamezole [0.024 mg/kg] IM) produced reliable and uneventful recoveries in all the procedures. During each anesthetic procedure, the animal was intubated and provided intermittent positive pressure ventilation with a megavertebrate demand ventilator. Tachycardia and hypoxia noted after induction resolved after positive pressure ventilation with oxygen. This report provides useful information on a novel anesthetic protocol used repeatedly for intensive medical management in a black rhinoceros.

Biochemical characterization of extracellular polymeric substances from endodontic biofilms.

Apical periodontitis is frequently associated with the presence of bacteria biofilm, which has an indisputable impact on the prognosis of endodontic therapy due to the high resistance to adverse environmental conditions, chemicals, and antibiotic therapy that characterize bacteria within biofilm. The biofilm matrix acts as a protective shield over the encased microorganisms. The aim of this investigation was to identify the main biochemical components of biofilm matrix from endodontic mono- and dual-species biofilms. Enterococcus faecalis and Actinomyces naeslundii were cultured as mono- and dual-species biofilms for 14 days. Crude extracellular polymeric substances (EPSs) from biofilm matrices were extracted using chemical and physical methods. High-performance liquid chromatography, gas chromatography, and mass spectrometry were used to determine the carbohydrate, protein, and fatty acid components. Chemical analysis of the biofilm matrices revealed that they were mainly composed of stachyose, maltose, and mannose carbohydrates. The protein profile in all biofilm samples showed abundant oxidoreductases and chaperone proteins and some virulence- associated proteins mainly located in the membrane surface. High percentages of saturated and monounsaturated fatty acids were identified in all biofilm matrices, with a major prevalence of palmitic, stearic, and oleic acids. Based on the results, it was possible to obtain for the first time a general overview of the biochemical profile of endodontic biofilm matrices.

Rapid evolution of decreased host susceptibility drives a stable relationship between ultrasmall parasite TM7x and its bacterial host.

Around one-quarter of bacterial diversity comprises a single radiation with reduced genomes, known collectively as the Candidate Phyla Radiation. Recently, we coisolated TM7x, an ultrasmall strain of the Candidate Phyla Radiation phylum Saccharibacteria, with its bacterial host Actinomyces odontolyticus strain XH001 from human oral cavity and stably maintained as a coculture. Our current work demonstrates that within the coculture, TM7x cells establish a long-term parasitic association with host cells by infecting only a subset of the population, which stay viable yet exhibit severely inhibited cell division. In contrast, exposure of a naïve A. odontolyticus isolate, XH001n, to TM7x cells leads to high numbers of TM7x cells binding to each host cell, massive host cell death, and a host population crash. However, further passaging reveals that XH001n becomes less susceptible to TM7x over time and enters a long-term stable relationship similar to that of XH001. We show that this reduced susceptibility is driven by rapid host evolution that, in contrast to many forms of phage resistance, offers only partial protection. The result is a stalemate where infected hosts cannot shed their parasites; nevertheless, parasite load is sufficiently low that the host population persists. Finally, we show that TM7x can infect and form stable long-term relationships with other species in a single clade of Actinomyces, displaying a narrow host range. This system serves as a model to understand how parasitic bacteria with reduced genomes such as those of the Candidate Phyla Radiation have persisted with their hosts and ultimately expanded in their diversity.

Actinomyces and Alimentary Tract Diseases: A Review of Its Biological Functions and Pathology.

Actinomyces are nonmotile, filamentous, Gram-positive bacteria that cause actinomycosis in immunodeficiency patients. Although the prognosis of actinomycosis is good, the diagnosis of actinomycosis is quite difficult. Recent studies on actinomycosis have shown that Actinomyces play an important role in various biological and clinical processes, such as the formation of dental plaque and the degradation of organics in the gastrointestinal tract. Here, the distribution of Actinomyces in the digestive tract, and different biological effects of actinomycosis, and its clinical association with inflammatory diseases are discussed. Furthermore, an overview of the most commonly used treatment methods and drugs used to treat Actinomyces infected alimentary canal diseases is presented.

Components in Lentinus edodes mushroom with anti-biofilm activity directed against bacteria involved in caries and gingivitis.

The present study investigated the compounds present in the low molecular mass fraction of Lentinus edodes mushroom (shiitake) extract and their anti-virulence activity against oral pathogens (reference and clinical Streptococcus mutans, Actinomyces naeslundii, and Prevotella intermedia strains). Oxalic, succinic, and quinic acids, and adenine, inosine, and uridine were identified by HPLC-DAD-ESI-MS/MS. Their anti-biofilm production and preformed biofilm disaggregation activities were studied using commercial standard compounds at different concentrations. As regards S. mutans, the highest activity was shown by adenine at 5 mg mL-1 both in the biofilm inhibition (BI 50%) and biofilm disaggregation tests (BD 20%). Considering A. naeslundii, BI values close to 80% were registered for oxalic acid at 1 mg mL-1 and 2 mg mL-1 and BD 50% for quinic acid at 3 mg mL-1. A weaker activity was found against P. intermedia. Furthermore, different mixtures of the commercial standards were tested showing that the activity of a compound can be strongly and sometimes negatively affected by the presence of the other compounds.

ent-Copalic acid antibacterial and anti-biofilm properties against Actinomyces naeslundii and Peptostreptococcus anaerobius.

Diterpenes are an important class of plant metabolites that can be used in the search for new antibacterial agents. ent-Copalic acid (CA), the major diterpene in Copaifera species exudates, displays several pharmacological properties. This study evaluates the CA antibacterial potential against the anaerobic bacteria Peptostreptococcus anaerobius and Actinomyces naeslundii. Antimicrobial assays included time-kill and biofilm inhibition and eradication assays. Time-kill assays conducted for CA concentrations between 6.25 and 12.5 µg/mL evidenced bactericidal activity within 72 h. CA combined with chlorhexidine dihydrochloride (CHD) exhibited bactericidal action against P. anaerobius within 6 h of incubation. As for A. naeslundii, the same combination reduced the number of microorganisms by over 3 log10 at 24 h and exerted a bactericidal effect at 48 h of incubation. CA at 500 and 2000 µg/mL inhibited P. anaerobius and A. naeslundii biofilm formation by at least 50%, respectively. CA at 62.5 and 1.000 µg/mL eradicated 99.9% of pre-formed P. anaerobius and A. naeslundii biofilms, respectively. These results indicated that CA presents in vitro antibacterial activity and is a potential biofilm inhibitory agent. This diterpene may play an important role in the search for novel sources of agents that can act against anaerobic bacteria.

Streptococcus gordonii Challisin protease is required for sensing cell--cell contact with Actinomyces oris.

The ability of microorganisms to regulate gene expression is thought to be critical for survival and growth during the development of polymicrobial biofilms such as dental plaque. The commensal dental plaque colonizer, Streptococcus gordonii, responds to cell--cell contact (coaggregation) with Actinomyces oris by regulating >20 genes, including those involved in arginine biosynthesis. We hypothesized that an S. gordonii extracellular protease is critical for sensing by providing amino acids that modulate gene expression. S. gordonii coaggregated strongly with A. oris in buffer, saliva or chemically defined medium (CDM). In wild-type S. gordonii, expression of arginine biosynthesis genes argC and argG increased within two hours' growth in CDM in monocultures, but not following coaggregation with A. oris. By contrast, coaggregation of A. oris with an S. gordonii mutant lacking sgc, encoding the extracellular protease Challisin, resulted in increases in argC and argG gene expression that were similar to monocultures. Genetic complementation of sgc restored the ability of S. gordonii to sense coaggregation with A. oris. Coaggregation enabled growth of S. gordonii in low/no arginine and disruption of sgc did not affect this ability. We propose that extracellular bacterial proteases may be key mediators of cell--cell contact sensing by diverse microbial species.