Browsing by Author "Alshammari, Abdullah Faraj"

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The Relationship Between Nitrate Reduction and Sulphur Metabolism in Health and Disease Associated Oral Bacteria
(Saudi Digital Library, 2023-07-14) Alshammari, Abdullah Faraj; Stephen, Abish; Allaker, Robert; Seoudi, Noha
Background: The oral microbiota plays a key role in the aetiopathogenesis of periodontitis. Whereby, nitrate-reducing bacteria (NRB) are associated with oral health, whereas sulphur metabolising bacteria (SMB) are associated with periodontitis. While the interplay between NRB and SMB within the oral cavity is recognised, the impact of interactions between these on oral health remains to be characterised. Method: All possible combinations of Porphyromonas gingivalis, Veillonella dispar, Actinomyces naeslundii and Streptococcus mutans at identical initial cell densities were cultured anaerobically with L-cysteine or potassium nitrate supplemented Brain Hearth Infusion broth. Nitrate-reductase and cysteine- desuflhydrase activities were assessed through colorimetric assays, and nitrate reductase gene expression (narG and narH) in A. naeslundii and V. dispar was measured using RT-qPCR. Results: Interactions were observed in the H2S production by co-cultures of P. gingivalis, A. naeslundii and V. dispar, with inhibition by S. mutans except with V. dispar. Synergistic and multiplicative interactions were observed in the nitrate reductase activity of A. naeslundii and V. dispar under nitrate supplementation. P. gingivalis or S. mutans in co-cultures with the NRB significantly enhanced or inhibited this activity respectively, while combining P. gingivalis and S. mutans together with both NRB species, restored the nitrate reductase activity. Gene expression data indicated that narG and narH expression were elevated in co- cultures compared to monocultures, however the expression was comparable across different combinations including with S. mutans. Conclusion: These data suggest that nitrate supplementation can enhance expression of nitrate reductases in NRB, however nitrate reduction may depend on other biotic or abiotic factors in the oral cavity. Strategies to increase nitrate reduction in the oral cavity to maintain or improve oral health should therefore consider ecological interactions prevalent in the oral niches.
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