The objective of this study was to characterize the oxygen dependent regulation of pyruvate oxidase （SpxB） gene expression and protein production in Streptococcus sanguinis （S. sanguinis）. SpxB is responsible for ...The objective of this study was to characterize the oxygen dependent regulation of pyruvate oxidase （SpxB） gene expression and protein production in Streptococcus sanguinis （S. sanguinis）. SpxB is responsible for the generation of growth-inhibiting amounts of hydrogen peroxide （H202） able to antagonize cariogenic Strepto- coccus mutans （S. mutans）. Furthermore, the ecological consequence of H202 production was investigated in its self-inhibiting ability towards the producing strain. Expression of spxB was determined with quantitative Real-Time RT-PCR and a fluorescent expression reporter strain. Protein abundance was investigated with FLAG epitope engineered in frame on the C-terminal end of SpxB. Self inhibition was tested with an antagonism plate assay. The expression and protein abundance decreased in cells grown under anaerobic conditions. S. sanguinis was resistant against its own produced H202, while cariogenic S. mutans was inhibited in its growth. The results suggest that S. sanguinis produces H202 as antimicrobial substance to inhibit susceptible niche competing species like S. mutans during initial biofilm formation, when oxygen availability allows for spxB expression and Spx production.展开更多
基金supported by NIH grants 4R00DE 018400 to Jens Kreth
文摘The objective of this study was to characterize the oxygen dependent regulation of pyruvate oxidase （SpxB） gene expression and protein production in Streptococcus sanguinis （S. sanguinis）. SpxB is responsible for the generation of growth-inhibiting amounts of hydrogen peroxide （H202） able to antagonize cariogenic Strepto- coccus mutans （S. mutans）. Furthermore, the ecological consequence of H202 production was investigated in its self-inhibiting ability towards the producing strain. Expression of spxB was determined with quantitative Real-Time RT-PCR and a fluorescent expression reporter strain. Protein abundance was investigated with FLAG epitope engineered in frame on the C-terminal end of SpxB. Self inhibition was tested with an antagonism plate assay. The expression and protein abundance decreased in cells grown under anaerobic conditions. S. sanguinis was resistant against its own produced H202, while cariogenic S. mutans was inhibited in its growth. The results suggest that S. sanguinis produces H202 as antimicrobial substance to inhibit susceptible niche competing species like S. mutans during initial biofilm formation, when oxygen availability allows for spxB expression and Spx production.
