ADHERENCE AND FIBRONECTIN-BINDING ARE ENVIRONMENTALLY REGULATED IN THE GROUP-A STREPTOCOCCI

The ability of the pathogenic Gram-positive bacterium Streptococcus py ogenes (group A streptococcus) to bind fibronectin and adhere to respi ratory epithelial cells is dependent on a surface protein called prote in F. In this study, we have examined the regulation of expression of protein F and have shown that it is environmentally regulated in respo nse to alterations in atmosphere. In six recent clinical isolates, exp ression of protein F was repressed during growth under reduced concent rations of O2. Expression in an anaerobic environment was induced by b oth superoxide-generating and redox-altering reagents. However, regula tion did not involve mry, a gene that controls expression of several s treptococcal surface proteins. Protein F was constitutively expressed in one of two laboratory-passaged strains analysed, and in a complemen tation analysis using an allele of the gene that encodes protein F (pr tF) cloned from a regulated strain and expressed in a constitutive str ain, the constitutive phenotype was shown to be dominant in trans. Reg ulation, as monitored by fusion of prtF to a promoterless chlorampheni col acetyltransferase gene, involved transcriptional control. Environm entally induced alterations in protein F expression affected the abili ty of the bacterium to adhere to epithelial cells, which suggests that the ability to regulate expression of protein F may be important duri ng infection.