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The extracellular vesicles (ECV) and extracellular protein (EP) fractions of Bacteroides gingivalis W50 showed haemagglutinating (HA) activity towards sheep erythrocytes. Similar fractions from the nonpathogenic strain W50/BE1 did not haemagglutinate. W50 ECV HA activity was not inhibited by various glycosidase, phospholipase or protease pretreatments, sugars or amino acids, including arginine or lysine. The haemagglutinating activity of ECV was associated only with the extracellular vesicle membrane. The EP and ECV of both strains displayed haemolytic activity. This activity was apparently depressed in the presence of 10 mM dithiothreitol (DTT). All EP and ECV fractions degraded certain structural sheep erythrocyte membrane proteins. The greatest activity was displayed by W50 ECV and W50/BE1 EP and was enhanced by DTT. In the presence of DTT, the ECV of both strains degraded purified human haemoglobin but this activity was greatly reduced in its absence.

The distribution of trypsin-like enzyme activity was studied in 48- and 72-h batch cultures of Bacteroides gingivalis W50 and an avirulent variant (W50/BE1) of the parent strain. Activity was measured at pH 7.4 in cells, the extracellular vesicle (ECV) and soluble extracellular protein (EP) fractions recovered by ammonium sulphate precipitation from spent growth medium. Both organisms produced cell surface and extracellular vesicles, but whilst strain W50 produced more ECV, W50/BE1 yielded more of the EP fraction by weight. Whole cultures of W50 displayed a three-fold greater trypsin activity than those of W50/BE1. However, 90% of the total enzyme activity of W50 cultures was associated with the particulate fraction (cells and ECV totalled), whereas this fraction accounted for only 10-30% of the total for W50/BE1. Unlike W50/BE1, the specific activities of W50 cells and ECV rose in 72-h cultures. Conversely, cultures of W50/BE1 displayed an increase in the yield and specific activity of the EP fraction.