Polyphosphate-Accumulating Bacteria: Potential Contributors to Mineral Dissolution in the Oral Cavity

Fluoride and gallein inhibit polyphosphate accumulation by oral pathogen Rothia dentocariosa

The uptake and storage of extracellular orthophosphate (Pi) by polyphosphate (polyP) accumulating bacteria may contribute to mineral dissolution in the oral cavity. To test the effect of potential inhibitors of polyP kinases on Rothia dentocariosa, gallein (0, 25, 50, and 100 μM) and fluoride (0, 50, and 100 ppm) were added to R. dentocariosa cultures grown in brain-heart infusion broth. At a late log growth phase (8 h), extracellular Pi was measured using an ascorbic acid assay, and polyP was isolated from bacterial cells treated with RNA/DNAases using a neutral phenol/chloroform extraction. Extracts were hydrolyzed and quantified as above. Gallein and fluoride had minor effects on bacterial growth with NaF having a direct effect on media pH. Gallein (≥25 μM) and fluoride (≥50 ppm) attenuated the bacterial drawdown of extracellular Pi by 56.7% (P < 0.05) and 37.3% (P < 0.01). There was a corresponding polyP synthesis decrease of 73.2% (P < 0.0001) from gallein and 83.1% (P < 0.0001) from fluoride. Attenuated total reflectance-Fourier-transform infrared spectroscopy validated the presence of polyP and its reduced concentration in R. dentocariosa bacterial cells following gallein and fluoride treatment. Rothia dentocariosa can directly change extracellular Pi and accumulate intracellular polyP, but the mechanism is attenuated by gallein and NaF.

Functional Genetic Diversity and Plant Growth Promoting Potential of Polyphosphate Accumulating Bacteria in Soil

Polyphosphate (polyP) accumulation is an important trait of microorganisms. Implication of polyP accumulating bacteria (PAB) in enhanced biological phosphate removal, heavy metal sequestration, and dissolution of dental enamel is well studied. Phosphorous (P) accumulated within microbial biomass also regulates labile P in soil; however, abundance and diversity of the PAB in soil is still unexplored. Present study investigated the genetic and functional diversity of PAB in rhizosphere soil. Here, we report the abundance of Pseudomonas spp. as high PAB in soil, suggesting their contribution to global P cycling. Additional subset analysis of functional genes i.e., polyphosphate kinase (ppk) and exopolyphosphatase (ppx) in all PAB, indicates their significance in bacterial growth and metabolism. Distribution of functional genes in phylogenetic tree represent a more biologically realistic discrimination for the two genes. Distribution of ppx gene disclosed its phylogenetic conservation at species level, however, clustering of ppk gene of similar species in different clades illustrated its environmental condition mediated modifications. Selected PAB showed tolerance to abiotic stress and strong correlation with plant growth promotary (PGP) traits viz. phosphate solubilization, auxin and siderophore production. Interaction of PAB with A. thaliana enhanced the growth and phosphate status of the plant under salinity stress, suggestive of their importance in P cycling and stress alleviation.

IMPORTANCE Study discovered the abundance of Pseudomonas genera as a high phosphate accumulator in soil. The presence of functional genes (polyphosphate kinase [ppk] and exopolyphosphatase [ppx]) in all PAB depicts their importance in polyphosphate metabolism in bacteria. Genetic and functional diversity reveals conservation of the ppx gene at species level. Furthermore, we found a positive correlation between PAB and plant growth promotary traits, stress tolerance, and salinity stress alleviation in A. thaliana.

Morphogenetic (Mucin Expression) as Well as Potential Anti-Corona Viral Activity of the Marine Secondary Metabolite Polyphosphate on A549 Cells

The mucus layer of the nasopharynx and bronchial epithelium has a barrier function against inhaled pathogens such as the coronavirus SARS-CoV-2. We recently found that inorganic polyphosphate (polyP), a physiological, metabolic energy (ATP)-providing polymer released from blood platelets, blocks the binding of the receptor binding domain (RBD) to the cellular ACE2 receptor in vitro. PolyP is a marine natural product and is abundantly present in marine bacteria. Now, we have approached the in vivo situation by studying the effect of polyP on the human alveolar basal epithelial A549 cells in a mucus-like mucin environment. These cells express mucins as well as the ectoenzymes alkaline phosphatase (ALP) and adenylate kinase (ADK), which are involved in the extracellular production of ATP from polyP. Mucin, integrated into a collagen-based hydrogel, stimulated cell growth and attachment. The addition of polyP to the hydrogel significantly increased cell attachment and also the expression of the membrane-tethered mucin MUC1 and the secreted mucin MUC5AC. The increased synthesis of MUC1 was also confirmed by immunostaining. This morphogenetic effect of polyP was associated with a rise in extracellular ATP level. We conclude that the nontoxic and non-immunogenic polymer polyP could possibly also exert a protective effect against SARS-CoV-2-cell attachment; first, by stimulating the innate antiviral response by strengthening the mucin barrier with its antimicrobial proteins, and second, by inhibiting virus attachment to the cells, as deduced from the reduction in the strength of binding between the viral RBD and the cellular ACE2 receptor.

Antibacterial and Remineralization Efficacy of Casein Phosphopeptide, Glycomacropeptide Nanocomplex, and Probiotics in Experimental Toothpastes: An In Vitro Comparative Study

Objective  This article evaluates the antibacterial and remineralization potential of experimentally prepared toothpastes containing different mixtures of nano casein phosphopeptides (nCPP), nano amorphous calcium phosphate (nACP), probiotic ­ Lactobacillus rhamnosus B-445 ( L. rhamnosus ), and nano glycomacropeptide (nGMP).

Materials and Methods  Five experimental toothpaste samples were prepared and grouped, such that group (A0) was the experimental toothpaste base formula. Groups (A1), (A2), (A3), and (A4) were the experimental toothpastes containing: nCPP; nCPP and nACP; nCPP, nACP, and L. rhamnosus , and nCPP, nACP, and nGMP, ­respectively. Group (A5) was the commercial group (GC MI Paste Plus). The five groups were screened against Streptococcus mutans (ATCC 25175) growth, and investigated for their remineralizing potentials on demineralized bovine enamel using Vickers ­microhardness test (Vickers hardness number [VHN]). Scanning electron microscope (SEM) images were obtained for the demineralized and remineralized enamel of the two most effective toothpastes against in vitro bacterial induced enamel demineralization. Statistical analysis was performed using one-way analysis of variance (ANOVA) as well as repeated measures ANOVA followed by Tukey’s post hoc test.

Results  Both (A3) and (A4) were significantly higher in mean inhibition zone ­diameters than group (A1) and (A2). Group (A4) showed the highest statistical ­significance in the mean difference between VHN values of demineralization and 15 days remineralization period. SEM images showed the deposition of nano-sized particles fill the ­microrough surface pattern of the etched enamel.

Conclusion  All these findings suggest the use of probiotic, nCPP–nACP, and nGMP as a dental anticariogenic and remineralizing active agents.

Geochemical Characteristics of Dolomitic Phosphorite Containing Rare Earth Elements and Its Weathered Ore

In order to provide a good theoretical guidance for the development and utilization of weathered phosphorite resources, we investigated the geochemical and mineralogical characteristics of primary and weathered phosphorites. The analysis of trace elements showed that the primary ore has hydrothermal sedimentation effect in the later stage, the weathered ore has obvious residual enrichment and the phosphate ore belongs to clastic lithologic phosphate rock. In addition, through leaching test method, it was shown that rare earth elements are present in fluorapatite in the form of isomorphic substitution, and the proportion of rare earth elements adsorbed on clay and other minerals was likely to be between 2% and 3%. The light rare earth elements are relatively enriched in both primary and weathered phosphorite, and Ce and Eu have obvious negative anomalies. The primary phosphorite is a dolomitic phosphorite containing rare earth elements, which are naturally enriched by weathering, and its weathered ore has obvious residual enrichment, while the deposit was characterized by normal marine sedimentation and hydrothermal action.

Sustained Release of Phosphates From Hydrogel Nanoparticles Suppresses Bacterial Collagenase and Biofilm Formation in vitro

Intestinal disease or surgical intervention results in local changes in tissue and host-derived factors triggering bacterial virulence. A key phenotype involved in impaired tissue healing is increased bacterial collagenase expression which degrades intestinal collagen. Antibiotic administration is ineffective in addressing this issue as it inadvertently eliminates normal flora while allowing pathogenic bacteria to "bloom" and acquire antibiotic resistance. Compounds that could attenuate collagenase production while allowing commensal bacteria to proliferate normally would offer major advantages without the risk of the emergence of resistance. We have previously shown that intestinal phosphate depletion in the surgically stressed host is a major cue that triggers P. aeruginosa virulence which is suppressed under phosphate abundant conditions. Recent findings indicate that orally administered polyphosphate, hexametaphosphate, (PPi) suppresses collagenase, and biofilm production of P. aeruginosa and S. marcescens in animal models of intestinal injury but does not attenuate E. faecalis induced collagenolytic activity (Hyoju et al., 2017). Systemic administration of phosphates, however, is susceptible to rapid clearance. Given the diversity of collagenase producing bacteria and the variation of phosphate metabolism among microbial species, a combination therapy involving different phosphate compounds may be required to attenuate pathogenic phenotypes. To address these barriers, we present a drug delivery approach for sustained release of phosphates from poly(ethylene) glycol (PEG) hydrogel nanoparticles. The efficacy of monophosphate (Pi)- and PPi-loaded NPs (NP-Pi and NP-PPi, respectively) and a combination treatment (NP-Pi + NP-PPi) in mitigating collagenase and biofilm production of gram-positive and gram-negative pathogens expressing high collagenolytic activity was investigated. NP-PPi was found to significantly decrease collagenase and biofilm production of S. marcescens and P. aeruginosa. Treatment with either NP-Pi or NP-Pi + NP-PPi resulted in more prominent decreases in E. faecalis collagenase compared to NP-PPi alone. The combination treatment was also found to significantly reduce P. aeruginosa collagenase production. Finally, significant attenuation in biofilm dispersal was observed with NP-PPi or NP-Pi + NP-PPi treatment across all test pathogens. These findings suggest that sustained release of different forms of phosphate confers protection against gram-positive and gram-negative pathogens, thereby providing a promising treatment to attenuate expression of tissue-disruptive bacterial phenotypes without eradicating protective flora over the course of intestinal healing.

The Saliva Metabolome in Association to Oral Health Status

Periodontitis is one of the most prevalent oral diseases worldwide and is caused by multifactorial interactions between host and oral bacteria. Altered cellular metabolism of host and microbes releases a number of intermediary end products known as metabolites. There is an increasing interest in identifying metabolites from oral fluids such as saliva to widen the understanding of the complex pathogenesis of periodontitis. It is believed that some metabolites might serve as indicators toward early detection and screening of periodontitis and perhaps even for monitoring its prognosis in the future. Because contemporary periodontal screening methods are deficient, there is an urgent need for novel approaches in periodontal screening procedures. To this end, we associated oral parameters (clinical attachment level, periodontal probing depth, supragingival plaque, supragingival calculus, number of missing teeth, and removable denture) with a large set of salivary metabolites ( n = 284) obtained by mass spectrometry among a subsample ( n = 909) of nondiabetic participants from the Study of Health in Pomerania (SHIP-Trend-0). Linear regression analyses were performed in age-stratified groups and adjusted for potential confounders. A multifaceted image of associated metabolites ( n = 107) was revealed with considerable differences according to age groups. In the young (20 to 39 y) and middle-aged (40 to 59 y) groups, metabolites were predominantly associated with periodontal variables, whereas among the older subjects (≥60 y), tooth loss was strongly associated with metabolite levels. Metabolites associated with periodontal variables were clearly linked to tissue destruction, host defense mechanisms, and bacterial metabolism. Across all age groups, the bacterial metabolite phenylacetate was significantly associated with periodontal variables. Our results revealed alterations of the salivary metabolome in association with age and oral health status. Among our comprehensive panel of metabolites, periodontitis was significantly associated with the bacterial metabolite phenylacetate, a promising substance for further biomarker research.

Galactose Impacts the Size and Intracellular Composition of the Asaccharolytic Oral Pathobiont Porphyromonas gingivalis

The asaccharolytic anaerobe Porphyromonas gingivalis metabolizes proteins it encounters in the periodontal pocket, including host-derived glycoproteins such as mucins and immunoglobulins. Often, these proteins are protected by a diverse array of carbohydrates tethered to the polypeptide chain via glycolytic bonds, and P. gingivalis produces enzymes capable of liberating these carbohydrates, exposing the proteinaceous core. In this study, we investigated the effect of individual monosaccharides, including galactose, l-fucose, mannose, and glucose, on the growth and physiology of P. gingivalis Of the carbohydrates tested, only galactose noticeably altered the density of the bacterial culture, and we observed that cultures grown with galactose reached significantly higher densities during stationary phase. Importantly, electron micrographs and plating of P. gingivalis in stationary phase demonstrated that the presence of galactose did not increase cell numbers; instead, the higher densities resulted from the expansion of individual cells which contained large intracellular granules. Initial attempts to characterize these granules revealed only a subtle increase in soluble carbohydrates, suggesting they are likely not composed of stored carbohydrate. Also, an analysis of major surface polysaccharides via an enzyme-linked immunosorbent assay (ELISA) did not reveal significant differences between cells grown with or without galactose. Finally, an initial investigation of the transcriptional changes elicited by galactose in late exponential phase suggested that genes important for cell shape and for the general stress response may play roles in this phenomenon. Overall, galactose, a monosaccharide commonly present on the surfaces of host proteins, substantially alters the physiology of P. gingivalis via the production of large, currently undefined, intracellular granules.IMPORTANCE Environmental perturbations are central to the ability of pathobionts, such as Porphyromonas gingivalis, to promote the development of diseased sites. In the case of periodontal disease, increased local pH, a shift to anaerobic surroundings, and the accumulation of Gram-negative anaerobes at the expense of Gram-positive cocci are known ecological fluctuations prominently associated with progression toward disease. Importantly, in contrast, the alterations to subgingival food webs in disease sites remain poorly characterized. We hypothesized that given the dramatic shift in community structure during disease, it is possible that free carbohydrates, which would typically be readily metabolized by Gram-positive cocci after cleavage from glycoproteins, may increase in concentration locally and thereby affect the physiological state of the subgingival microbiota. In this study, we explored the impact of free monosaccharides on P. gingivalis to gain deeper insight into the effect of dysbiotic conditions on the growth and physiology of this periodontal pathogen.

Biomimetic transformation of polyphosphate microparticles during restoration of damaged teeth

OBJECTIVE

In the present study, we investigated the fusion process between amorphous microparticles of the calcium salt of the physiological polymer comprising orthophosphate units, of inorganic polyphosphate (polyP), and enamel.

METHODS

This polymer was incorporated as an ingredient into toothpaste and the fusion process was studied by electron microscopy and by synchrotron-based X-ray tomography microscopy (SRXTM) techniques.

RESULTS

The data showed that toothpaste, supplemented with the amorphous Ca-polyP microparticles (aCa-polyP-MP), not only reseals tooth defects on enamel, like carious lesions, and dentin, including exposed dentinal tubules, but also has the potential to induce re-mineralization in the enamel and dentin regions. The formation of a regeneration mineralic zone on the tooth surface induced by aCa-polyP-MP was enhanced upon exposure to artificial saliva, as demonstrated by SRXTM. Energy dispersive X-ray analysis revealed an increase in the calcium/phosphorus atomic ratio of the enamel deposits to values characteristic for the particles during the treatment with polyP applied in the toothpaste, indicating a fusion of the particles with the tooth mineral.

SIGNIFICANCE

Our results suggest that toothpaste enriched with aCa-polyP-MP is a promising biomimetic material for accelerating enamel and dentin restoration.

Polyphosphate in Lactobacillus and Its Link to Stress Tolerance and Probiotic Properties

The synthesis of the inorganic polymer polyphosphate (poly-P) in bacteria has been linked to stress survival and to the capacity of some strains to sequester heavy metals. In addition, synthesis of poly-P by certain strains of probiotic lactobacilli has been evidenced as a probiotic mechanism due to the homeostatic properties of this compound at the intestinal epithelium. We analyzed the link between poly-P synthesis, stress response, and mercury toxicity/accumulation by comparing wild-type strains of Lactobacillus and their corresponding mutants devoid of poly-P synthesis capacity (defective in the poly-P kinase, ppk, gene). Results showed that resistance to salt (NaCl) and acidic (pH 4) stresses upon ppk mutation was affected in Lactobacillus casei, while no effect was observed in two different Lactobacillus plantarum strains. Inorganic [Hg(II)] and organic (CH₃Hg) mercury toxicity was generally increased upon ppk mutation, but no influence was seen on the capacity to retain both mercurial forms by the bacteria. Notwithstanding, the culture supernatants of ppk-defective L. plantarum strains possessed a diminished capacity to induce HSP27 expression, a marker for cell protection, in cultured Caco-2 cells compared to wild-type strains. In summary, our results illustrate that the role of poly-P in stress tolerance can vary between strains and they reinforce the idea of probiotic-derived poly-P as a molecule that modulates host-signaling pathways. They also question the relevance of this polymer to the capacity to retain mercury of probiotics.