Genetic analysis of scrA and scrB from Streptococcus sobrinus 6715.
A DNA fragment containing scrA and scrB, which encode enzyme II of the phosphoenolpyruvate-dependent sucrose phosphotransferase system and sucrose-6-phosphate hydrolase, respectively, was isolated from a lambda gt10 genomic DNA library of Streptococcus sobrinus 6715. Both genes were located on a 4.2-kb DNA fragment which was maintained stably in Escherchia coli on low-copy-number vector pGB2. The recombinant E. coli clone expressed sucrose-hydrolytic activity on MacConkey agar base supplemented with raffinose or sucrose. Results from deletion analysis showed that the sucrose-metabolic activity was contained within a 3.5-kb region. The lactic acid bacterium Lactococcus lactis subsp. lactis LM0230, which is devoid of sucrose-metabolic activity, was used to study the enzyme activities encoded by scrA and scrB from S. sobrinus 6715. L. lactis transformants carrying the 4.2-kb S. sobrinus-derived DNA fragment on E. coli-Streptococcus shuttle vector pDL278 were able to grow at the expense of sucrose and exhibited enzyme II and sucrose-6-phosphate hydrolase activities. Results from hybridization studies and a comparison of the restriction endonuclease maps of the scrA- and scrB-containing chromosomal regions from S. mutans GS5 and S. sobrinus 6715 suggested considerable divergence.
Chen
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Department of Microbiology, University of Texas Health Science Center, San Antonio 78284-7758.
LeBlanc
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D015342:DNA Probes; D004269:DNA, Bacterial / Q000302:isolation & purification; D015723:Gene Library; D005798:Genes, Bacterial; D006026:Glycoside Hydrolases / Q000235:genetics*; D013294:Lactococcus lactis / Q000235:genetics / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics*; D016986:Streptococcus sobrinus / Q000235:genetics*; D013395:Sucrose / Q000378:metabolism; D043324:beta-Fructofuranosidase
D015342:DNA Probes; D004269:DNA, Bacterial; D013395:Sucrose; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C055701:phosphoenolpyruvate-sucrose phosphotransferase; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase