PROPERTIES OF A BACTERIOLYTIC ACTIVITY FROM AN ORAL GRAM-POSITIVE CLINICAL ISOLATE

The aim of this study was to characterise an oral bacterial isolate po ssessing extracellular bacteriolytic activity and to determine the bas ic properties of this activity. The lytic strain L1 was a gram-positiv e pleomorphic rod that grew only under anaerobic conditions. Glucose a nd raffinose were fermented whereas catalase and urease were not produ ced. The activity spectrum of a crude lytic fraction was restricted to strains of Actinomyces naeslundii and Actinomyces viscosus. On the ba sis of its molecular weight (>30 kDa) as well as sensitivity to beat a nd trypsin, the factor(s) has a proteinaceous component. The activity was highly sensitive to EDTA suggesting that cations may be essential for optimal activity. Sulfhydryl groups are also of major importance i n the lytic process as activity was highly stimulated by dithiothreito l and inhibited by p-chloromercuriphenylsulfonic acid. Strain L1 was f ound to grow on a solid basal medium containing heat-killed A. naeslun dii cells, and suggests a physiological role for the bacteriolytic act ivity. The bacteriolytic activity demonstrated in the present study ma y constitute a selective advantage for establishment of the bacteria i n a complex ecosystem like the oral cavity.