Molecular Oral Microbiology最新文献

Oral microbiome sequencing efforts revealed the presence of hundreds of different microbes. Interindividual differences at strain and species resolution suggest that microbiome diversity could lead to mechanistically distinct gene regulation as well as species-related differences in phenotypes. Commonly, gene regulation and related phenotypes are studied in a few selected strains of a particular species with conclusions that are mostly generalized. The aim of this study was to isolate several species of Corynebacterium using an established protocol that led to the previous isolation of C. durum. Characterization of C. durum interspecies interactions revealed a specific mechanism for chain elongation in Streptococcus sanguinis that was the result of corynebacterial fatty acid production and secretion. While the protocol was successfully applied to isolate what we presumed to be additional Corynebacterium based on several phenotypic traits that seem to be identical to C. durum, genome sequencing of the newly isolated strains placed them closer to Actinomyces. Both Corynebacterium and Actinomyces are suborders of the Actinobacteridae and related species. Our study suggests to take several comprehensive strategies into consideration when taxonomically identifying closely related microorganisms. Furthermore, it seems to be important to test common core phenotypes in bacterial ecology to understand the behavior of specific groups of microbes, rather than simply relying upon genome sequence homology to establish relationships in the microbiome.

Carbohydrate components, such as glycoconjugates and polysaccharides, are constituents of the dental biofilm matrix that play an important role in biofilm stability and virulence. Exopolysaccharides in Streptococcus mutans biofilms have been characterized extensively, but comparably little is known about the matrix carbohydrates in complex, in situ-grown dental biofilms. The present study employed fluorescence lectin binding analysis (FLBA) to investigate the abundance and spatial distribution of glycoconjugates/polysaccharides in biofilms (n = 306) from 10 participants, grown in situ with (SUC) and without (H2O) exposure to sucrose. Biofilms were stained with 10 fluorescently labeled lectins with different carbohydrate specificities (AAL, ABA, ASA, HPA, LEA, MNA-G, MPA, PSA, VGA and WGA) and analyzed by confocal microscopy and digital image analysis. Microbial composition was determined by 16S rRNA gene sequencing. With the exception of ABA, all lectins targeted considerable matrix biovolumes, ranging from 19.3% to 194.0% of the microbial biovolume in the biofilms, which illustrates a remarkable variety of carbohydrate compounds in in situ-grown dental biofilms. MNA-G, AAL, and ASA, specific for galactose, fucose, and mannose, respectively, stained the largest biovolumes. AAL and ASA biovolumes were increased in SUC biofilms, but the difference was not significant due to considerable biological variation. SUC biofilms were enriched in streptococci and showed reduced abundances of Neisseria and Haemophilus spp., but no significant correlations between lectin-stained biovolumes and bacterial abundance were observed. In conclusion, FLBA demonstrates the presence of a voluminous biofilm matrix comprising a variety of different carbohydrate components in complex, in situ-grown dental biofilms.

Interleukin-34 (IL-34) is a cytokine that supports the viability and differentiation of macrophages. An important cytokine for the development of epidermal immunity, IL-34, is present and plays a role in the immunity of the oral environment. IL-34 has been linked to inflammatory periodontal diseases, which involve innate phagocytes, including macrophages. Whether IL-34 can alter the ability of macrophages to effectively interact with oral microbes is currently unclear. Using macrophages derived from human blood monocytes with either the canonical cytokine colony-stimulating factor (CSF)1 or IL-34, we compared the ability of the macrophages to phagocytose, kill, and respond through the production of cytokines to the periodontal keystone pathogen Porphyromonas gingivalis. While macrophages derived from both cytokines were able to engulf the bacterium equally, IL-34-derived macrophages were much less capable of killing internalized P. gingivalis. Of the macrophage cell surface receptors known to interact with P. gingivalis, dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin was found to have the largest variation between IL-34- and CSF1-derived macrophages. We also found that upon interaction with P. gingivalis, IL-34-derived macrophages produced significantly less of the neutrophil chemotactic factor IL-8 than macrophages derived in the presence of CSF1. Mechanistically, we identified that the levels of IL-8 corresponded with P. gingivalis survival and dephosphorylation of the major transcription factor NF-κB p65. Overall, we found that macrophages differentiated in the presence of IL-34, a dominant cytokine in the oral gingiva, have a reduced ability to kill the keystone pathogen P. gingivalis and may be susceptible to specific bacteria-mediated cytokine modification.

The ecological dysbiosis of a biofilm includes not only bacterial changes but also changes in their metabolism. Related to oral biofilms, changes in metabolic activity are crucial endpoint, linked directly to the pathogenicity of oral diseases. Despite the advances in caries research, detailed microbial and metabolomic etiology is yet to be fully clarified. To advance this knowledge, a meta-taxonomic approach based on 16S rRNA gene sequencing and an untargeted metabolomic approach based on an ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry analysis (UHPLC/Q-TOF-MS) were conducted. To this end, an in vitro biofilm model derived from the saliva of healthy participants were developed, under commensal and cariogenic conditions by adding sucrose as the disease trigger. The cariogenic biofilms showed a significant increase of Firmicutes phyla (p = 0.019), due to the significant increase in the genus Streptococcus (p = 0.010), and Fusobacter (p < 0.001), by increase Fusobacterium (p < 0.001) and Sphingomonas (p = 0.024), while suffered a decrease in Actinobacteria (p < 0.001). As a consequence of the shift in microbiota composition, significant extracellular metabolomics changes were detected, showed 59 metabolites of the 120 identified significantly different in terms of relative abundance between the cariogenic/commensal biofilms (Rate of change > 2 and FDR < 0.05). Forty-two metabolites were significantly higher in abundance in the cariogenic biofilms, whereas 17 metabolites were associated significantly with the commensal biofilms, principally related protein metabolism, with peptides and amino acids as protagonists, latter represented by histidine, arginine, l-methionine, glutamic acid, and phenylalanine derivatives.

Streptococcus pyogenes, a host-restricted gram-positive pathogen during infection, initially adheres to the epithelia of the nasopharynx and respiratory tract of the human host, followed by disseminating to other organs and evading the host immune system. Upon phagocytosis, S. pyogenes encounters oxidative stress inside the macrophages. The role of polyamines in regulating various physiological functions including stress resistance in bacteria has been reported widely. Since S. pyogenes lacks the machinery for the biosynthesis of polyamines, the study aimed to understand the role of extracellular polyamines in the survival of S. pyogenes under oxidative stress environments. S. pyogenes being a catalase-negative organism, we report that its survival within the macrophages and H₂ O₂ is enhanced by the presence of spermidine. The increased survival can be attributed to the upregulation of oxidative stress response genes such as sodM, npx, and mtsABC. In addition, spermidine influences the upregulation of virulence factors such as sagA, slo, and hasA. Also, spermidine leads to a decrease in hydrophobicity of the cell membrane and an increase in hyaluronic acid. This study suggests a role for extracellular spermidine in the survival of S. pyogenes under oxidative stress environments. Recognizing the factors that modulate S. pyogenes survival and virulence under stress will assist in understanding its interactions with the host.