Potential role for age as a modulator of oral nitrate reductase activity
Khandaker Ahtesham AhmedK. C. KimKarina RicartWilliam Van Der PolXiaoping QiMarcas M. BammanChristian E. BehrensGordon FisherMichael E. BoultonCasey D. MorrowPamela V. O’NealRakesh P. Patel
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Oral Microbiome
This chapter summarizes the recent advancement of our knowledge of the healthy oral microbiome, and address the potential role of the oral microbiome in systemic diseases, including cardiovascular disease and pneumonia. An understanding of the composition of the oral microbial community with respect to oral health is essential for diagnosis, prevention, and treatment of oral diseases. The chapter describes oral microbiome associated with periodontal disease, microbiome associated with endodontic infections, apical periodontitis and tooth decay, and oral microbiome associated with oral cancer. Diseases caused by the oral microbiome are not limited to oral infections. Recognition that disease conditions associated with the oral microbiome contribute to systemic infections may require clinicians to consider alternative preventative and therapeutic approaches. The current data on two of the most-studied systemic conditions, cardiovascular and respiratory diseases are reviewed in the chapter. A community-and microbial ecology-based pathogenic concept that forms the basis for understanding relationships between the oral microbiome and the host, as well as developing novel strategies for therapeutics and disease prevention is discussed in the chapter. A better understanding of the oral microbiome structure and function and the dynamics between the commensals and pathogens is needed to selectively modulate composition of the microbiome and prevent oral disease.
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Nitrite reduction, catalyzed by nitrite reductase, is a key step in the denitrification pathway because it catalyzes the reduction of soluble nitrite (NO2-) into nitric oxide gas (NO). The production of nitric oxide gas therefore decreases the amount of nitrogen in soils. Other studies have investigated the effect of oxygen on denitrification in a few specific microorganisms (e.g. Aquaspirillum magnetotacticum, Thiosphaera pantotropha, and Paracoccus denitrificans). In this study, we tested the effect of oxygen on nitrite reduction in seven strains representing 5 different genera obtained from Tallgrass Prairie soil. The strains were chosen based on positive detection of at least one functional gene in the denitrification pathway along with positive results for nitrate (NO3-) and/or nitrite reduction after growth in nitrate broth in a microtiter plate assay. Under these conditions which did not totally exclude oxygen, three strains were able to reduce nitrite while four strains did not reduce nitrite. All seven strains were retested for the production/consumption of nitrite under strictly anaerobic conditions using nitrate as the electron acceptor. In addition, the strains were screened for genes encoding the copper nitrite reductase (nirK) and the cytochrome cd1-nitrite reductase (nirS) and other functional markers of denitrification pathway, namely nitric oxide reductase gene (norB) and nitrous oxide (N2O) reductase gene (nosZ) by PCR amplification using specific primers. Our results show that under strict anaerobic conditions, two additional strains demonstrated nitrite reduction. Although none of the molecular markers showed perfect correlation with the ability to reduce nitrite, nirS/nirK, commonly used to screen environmental samples for denitrifying bacteria, was detected in only two of the five strains shown in this study to reduce nitrite. More nitrite reducing strains were correctly identified when both the cnorB and nosZ primer sets were used. ©2015 Oklahoma Academy of Science
Paracoccus denitrificans
Nitrous-oxide reductase
Aerobic denitrification
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Commensal microbiomes exert critical functions at barrier sites. In particular, establishment of the commensal microbiome after birth dictates immune functionality and tissue homeostasis at mucosal surfaces. To investigate the establishment and stability of the oral mucosal microbiome in mice, we evaluated oral microbiome communities shortly after birth, through adulthood, and up to 1 y of life in a controlled manner, using sequential oral samples from the same mice over time. We further evaluated transmissibility of oral microbiomes from parents and during cohousing experiments and evaluated susceptibility to oral inflammatory disease in mice harboring distinct microbiomes. Our work reveals basic principles in the establishment and stability of a health-associated oral microbiome after birth and provides insights that may be important for host-microbiome experimentation in animal models.
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Abstract The onset and progress of dental caries and periodontal disease is associated with the oral microbiome. Therefore, it is important to understand the factors that influence oral microbiome formation. One of the factors that influence oral microbiome formation is the transmission of oral bacteria from parents. However, it remains unclear when the transmission begins, and the difference in contributions of father and mother. Here, we focused on the oral microbiome of 18-month-old infants, at which age deciduous dentition is formed and the oral microbiome is likely to become stable, with that of their parents. We collected saliva from forty 18-month-old infants and their parents and compared the diversity and composition of the microbiome using next-generation sequencing of 16S rRNA genes. The results showed that microbial diversity in infants was significantly lower than that in parents and composition of microbiome were significantly different between infants and parents. Meanwhile, the microbiome of the infants was more similar to that of their mothers than unrelated adults. The bacteria highly shared between infants and parents included not only commensal bacteria but also disease related bacteria. These results suggested that the oral microbiome of the parents influences that of their children aged < 18 months.
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The purpose of this scoping review was to examine the oral microbiome composition in preterm infants, sampling and collection methods, as well as exposures associated with oral microbiome composition and health implications. We conducted a scoping review of the literature using the Arskey and O'Malley framework. We identified a total of 13 articles which met our inclusion criteria and purpose of this scoping review. Articles included in this review compared the oral microbiome in preterm infants to term infants, examined alterations to the oral microbiome over time, compared the oral microbiome to different body site microbiomes, and explored associations with clinically relevant covariates and outcomes. Exposures associated with the diversity and composition of the oral microbiome in preterm infants included delivery mode, oral feeding, oropharyngeal care, skin-to-skin care, and antibiotics. Day of life and birth weight were also associated with oral microbiome composition. The oral microbiome may be associated with the composition of the tracheal and gut microbiomes, likely due to their proximity. Alpha and beta diversity findings varied across studies as well as the relative abundance of taxa. This is likely due to the different sampling techniques and timing of collection, as well as the wide range of infant clinical characteristics. Multiple factors may influence the composition of the oral microbiome in preterm infants. However, given the heterogeneity of sampling techniques and results within this review, the evidence is not conclusive on the development as well as short- and long-term implications of the oral microbiome in preterm infants and needs to be explored in future research studies. Key Points
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Plants take up nitrogen in the form of nitrate and ammonia through nitrate assimilation pathway.Nitrate assimilation is highly regulated process by two successive enzymes,nitrate reductase (NR) and nitrite reductase (NiR),which mainly controll the primary nitrogen assimilation.In higher plants,various external and endogenous factors influence the regulation of NR and NiR gene expression transcriptionally as well as post-transcriptionally.Post-translational modulation is an important mechanism to eliminate the accumulation of nitrite.Development of molecular biology methods will contribute to the research of regulatory networks of NR and NiR by creating mutants and transgenic lines.
Nitrogen Assimilation
Assimilation (phonology)
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The human mouth houses the second most diverse microbial community in the body, with almost 700 species of bacteria colonizing the hard surfaces of teeth and the soft tissues of the oral mucosa. To compete in the relatively exposed oral cavity, resident microbes must avoid being replaced by newcomers. This selective constraint, coupled with pressure on the host to cultivate a beneficial microbiome, has rendered a commensal oral microbiota that displays colonization resistance, protecting the human host from invasive species, including pathogens. Current control of dental plaque-related diseases is non-specific and is centered on the removal of plaque by mechanical means. Several new methods based on the modulation of the microbiome that aim at maintaining and re-establishing a healthy oral ecosystem have been developed and has greatly expanded our knowledge of the composition and function of the oral microbiome in health and disease. Promoting a balanced microbiome is therefore important to effectively maintain or restore oral health. This review provides an updated body of knowledge on oral microbiome in health and disease and discusses the implications for modern-day oral healthcare. Filipino Oral Microbiome Research to develop a policy framework for microbiome-based management of dental diseases and opportunities will be discussed.
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Although the effects of environmental changes on extractable nitrate reductase activity are well documented, little attention has been paid to the response of nitrite reductase to similar treatments. We have followed changes in the level of extractable nitrate and nitrite reductase in the leaves of pea seedlings subjected to different light, shade, drought, and nitrate treatments. In similarity to nitrate reductase, extractable nitrite reductase increases with availability of nitrate. However, it appears that the two enzyme activities show differential responses in plants exposed to drought conditions and in plants transferred to darkness. Nitrate reductase activity declines much more rapidly than nitrite reductase. These observations and the varying influence of the other environmental treatments are discussed in relation to the different cellular locations of nitrate and nitrite reductase.
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Abstract This Basic Science Workshop addressed the oral microbiome. At the 7th World Workshop on Oral Health & Disease in HIV/AIDS in India in 2014, some aspects of the human microbiome were discussed, and research questions formulated. Since that time, there have been major advances in technology, which have stimulated a number of publications on many aspects of the human microbiome, including the oral cavity. This workshop aimed to summarize current understanding of the “normal” microbiome of the oral cavity compared to that during HIV infection, and how oral immune factors and other clinical variables alter or control the oral microbiome. An important question is whether successful treatment with anti‐retroviral therapy, which leads to a significant drop in viral loads and immune reconstitution, is associated with any change or recovery of the oral microbiome. Additionally, the workshop addressed the issue of which parameters are most appropriate/correct to evaluate the oral microbiome and how clinically relevant are shifts/changes in the oral microbiome. The workshop evaluated current knowledge in five research areas related to five basic questions and identified further topics where further research is required.
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The oral cavity has the second largest and diverse microbiota after the gut harboring over 700 species of bacteria. It nurtures numerous microorganisms which include bacteria, fungi, viruses and protozoa. The mouth with its various niches is an exceptionally complex habitat where microbes colonize the hard surfaces of the teeth and the soft tissues of the oral mucosa. In addition to being the initiation point of digestion, the oral microbiome is crucial in maintaining oral as well as systemic health. Because of the ease of sample collection, it has become the most well-studied microbiome till date. Previously, studying the microbiome was limited to the conventional culture-dependent techniques, but the abundant microflora present in the oral cavity could not be cultured. Hence, studying the microbiome was difficult. The emergence of new genomic technologies including next-generation sequencing and bioinformatics has revealed the complexities of the oral microbiome. It has provided a powerful means of studying the microbiome. Understanding the oral microbiome in health and disease will give further directions to explore the functional and metabolic alterations associated with the diseased states and to identify molecular signatures for drug development and targeted therapies which will ultimately help in rendering personalized and precision medicine. This review article is an attempt to explain the different aspects of the oral microbiome in health.
Oral Microbiome
Human Microbiome Project
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