IADR Abstract Archives
Anaerobic Growth of Oral Neisseria and Rothia Species
Objectives: Dental plaque is an anaerobic environment, yet obligate aerobes such as Neisseria and Rothia spp. are frequently detected and it is hypothesised that they are using alternative electron acceptors. The aim of this study was to investigate the effect of media supplementation with nitrate, nitrite, sulphate or formate on anaerobic growth of Neisseria and Rothia spp.
Methods: The growth of type strains of 5 Neisseria spp. and 3 Rothia spp. was assessed on Blood Agar base and in Brain Heart Infusion broth, supplemented with 0-50 mM sodium nitrate, nitrite, sulphate or formate. Whole genome sequences of the strains were inspected for the presence of relevant enzymes.
Results: All strains grew well in air but did not grow, or grew poorly (+) anaerobically. Supplementation of agar with nitrate allowed good anaerobic growth (+++) of Neisseria bacilliformis, Neisseria mucosa and the Rothia spp. In nitrate-containing broth, the same species displayed a 2 to 11-fold increase in maximum optical density (ODmax) compared to the control. Genomic analysis confirmed that these species contain a respiratory nitrate reductase. No similar genes were found in the remaining species. Moderate growth (++) of N. bacilliformis and N. mucosa was observed in agar media supplemented with up to 25 mM nitrite in agar, and for Neisseria subflava and Neisseria sicca up to 10 mM nitrite. ODmax was increased 1 to 6-fold for N. bacilliformis, N. mucosa and N. subflava after anaerobic incubation in broth supplemented with nitrite. Nitrite did not support anaerobic growth of Rothia spp. and Neisseria flavescens. Concentrations of nitrite >25 mM inhibited aerobic growth of all strains. Sulphate and formate did not stimulate any growth of any strain.
Conclusions: Nitrate and nitrite can be used by some Neisseria and Rothia spp. as electron acceptors, allowing growth of these obligate aerobes under anaerobic conditions.
Methods: The growth of type strains of 5 Neisseria spp. and 3 Rothia spp. was assessed on Blood Agar base and in Brain Heart Infusion broth, supplemented with 0-50 mM sodium nitrate, nitrite, sulphate or formate. Whole genome sequences of the strains were inspected for the presence of relevant enzymes.
Results: All strains grew well in air but did not grow, or grew poorly (+) anaerobically. Supplementation of agar with nitrate allowed good anaerobic growth (+++) of Neisseria bacilliformis, Neisseria mucosa and the Rothia spp. In nitrate-containing broth, the same species displayed a 2 to 11-fold increase in maximum optical density (ODmax) compared to the control. Genomic analysis confirmed that these species contain a respiratory nitrate reductase. No similar genes were found in the remaining species. Moderate growth (++) of N. bacilliformis and N. mucosa was observed in agar media supplemented with up to 25 mM nitrite in agar, and for Neisseria subflava and Neisseria sicca up to 10 mM nitrite. ODmax was increased 1 to 6-fold for N. bacilliformis, N. mucosa and N. subflava after anaerobic incubation in broth supplemented with nitrite. Nitrite did not support anaerobic growth of Rothia spp. and Neisseria flavescens. Concentrations of nitrite >25 mM inhibited aerobic growth of all strains. Sulphate and formate did not stimulate any growth of any strain.
Conclusions: Nitrate and nitrite can be used by some Neisseria and Rothia spp. as electron acceptors, allowing growth of these obligate aerobes under anaerobic conditions.