Kenshiro Takamori

Subcellular localization of D-glucanases in Bacteroides oralis Ig4a.

Three D-glucan-hydrolysing enzymes from Bacteroides oralis Ig4a have been isolated. Two of them are dextranases which hydrolyse (1----6) but not (1----3) linked alpha-D-glucans; one (EC 3.2.1.11, 1,6-alpha-D-glucan 6-glucanohydrolase) is localized in the periplasm, and the other, which is an exo-enzyme (EC 3.2.1.70, 1,6-alpha-D-glucan glucohydrolase), in the cytoplasm. The third is a mutanase (EC 3.2.1.59, 1,3-(1,3;1,4)-alpha-D-glucan 3-glucanohydrolase) that hydrolyses (1----3) but not (1----6) linked alpha-D-glucans, and is present only in the cytoplasm.

Preliminary Studies of Fructan-Hydrolyzing Bacteria from Human Dental Plaque

Fructans in dental plaque contain two different types of fructopolysaccharides : one is the levan-type with (2,6)-linked ƒA-fructofuranoside residues and the other is the inulin-type with (2,1)-linked jS-fructofuranoside residues (4). Fructans formed in plaque serve as an exogenous carbohydrate source for plaque bacteria (11), and become gradually hydrolyzed by such bacteria, resulting in continued acid

Dextran Degrading Bacteria in Rat Oral Cavity

Dextran degrading activity of bacteria in the mouth of Wister rat was studied. Weaning rats were divided into two groups, one was fed cariogenic diet, 6-PMV, and the other fed ordinary diet. After breeding for 2 weeks, dental plaque material was collected, and inoculated into Tryp-tose-Yeast extract broth containing 0.2% Dextran T-2, 000 (Pharmacia, M. W. 2, 000, 000), and incubated at 37C for 24 h aerobically or anaerobically. To the supernatant of the culture was added ethanol to 55% to 60% by volume, and remaining dextran was determined. At the same time, dextran degrading bacteria were isolated from the plaque materials.The results obtained are as follows:1) Dextran degrading activity was observed in both groups, one bred with cariogenic diet and the other with ordinary diet, but the former was more active than the latter.2) Several types of bacteria showed to have dextran degrading activity in the plaque of rats.3) Anerobic culture assumed dextran more than aerobic culture. This result indicated that anaerobes are more predominant in the plaque for degrading dextran than aerobes.4) A representative organism which degrades dextran was anaerobic, gram negative rod, and identified as Bacteroides fragilis by its biochemical and serological characteristics.