Fenotypiska förändringar av orala streptokocker vid olika tillväxtförhållande : Syrepåverkan på streptokockers tillväxtmönster

Sammanfattning

Streptococci dominate the oral microbiota, and different species can be distinguished through biochemical tests that rely on their phenotypic characteristics. The aim of this study is to investigate how Streptococcus oralis, Streptococcus constellatus, and Streptococcus gordonii are affected by oxygen levels (aerobic and anaerobic conditions). Their phenotypic traits are examined using growth curves based on optical density measurements (OD 600 nm) and colony-forming units (CFU/ml), along with biochemical analyses assessing enzyme activity and metabolic products. Results: S. constellatus, S. gordonii, and S. oralis showed a metabolic adaptation to microaerophilic environments, where oxygen acts as a metabolic modulator in their processes. S. oralis displays flexibility by growing under both aerobic and anaerobic conditions, while S. gordonii grows best in aerobic conditions. In contrast, S. constellatus thrives in anaerobic environments and shows a more anaerobic metabolism profile. Significant differences in enzyme activity were observed among all three species under the tested conditions, especially in arginine, aesculine metabolism and hemolysis. Our results confirm that oxygen level is an important factor that influences metabolism and enzymatic activity in oral streptococci. These environmental factors lead to considerable phenotypic variation both within and between species. It is therefore crucial that future scientific studies focus on mapping the underlying mechanisms responsible for these phenotypic changes in commensal bacteria in response to environmental shifts. In particular, further research should explore how these phenotypic adaptations affect bacterial co-aggregation and their roles in biofilm formation.