EXPRESSION AND SECRETION OF AN ARTHROBACTER DEXTRANASE IN THE ORAL BACTERIUM STREPTOCOCCUS-GORDONII

We have constructed a plasmid to express and secrete dextranase in the oral bacterium Streptococcus gordonii. The dextranase gene from Arthr obacter sp. strain CB-8 was linked to a promoter and a DNA sequence en coding the signal peptide of Streptococcus downei glucosyltransferase I (gtfI) followed by the Escherichia coli rrnBt1t2 terminator and inse rted in the shuttle vector pVA838. S. gordonii transformed with this p lasmid (pMNK-4) expressed and secreted mature Arthrobacter dextranase. The transformant was found to repress the firm adherence of water-ins oluble glucan in a coculture experiment with cariogenic bacteria, Stre ptococcus sobrinus, in the presence of sucrose. Such genetically engin eered oral bacteria could provide a therapy to prevent dental caries.