歯垢内におけるmaltoseの有機酸産生能について

歯垢は、Streptococcus mutans(S.mutans)菌の持っglucosyltransferaseがsucroseを分解して粘性で非水溶性のpolyglucanを合成し、歯面に付着させることで起こる。う蝕は、歯垢中に種々の糖が浸透して、S.mutans菌が持つ酵素によって代謝され、有機酸を生成して歯垢中のpHを下げ、エナメル質を脱灰することによって起こると言われている。各種糖類のうち、maltoseが歯垢中のpHを低下させるかどうかについては、種々の報告があり、未だ明らかではない。そこで、各種糖類による菌体合成能と有機酸生成能を基礎的に観察した。その結果、(1)試験管壁への菌体付着量は、sucrose入り培地で最も多く、starch入り培地、maltose入り培地では菌体の付着は観察されなかった。(2)金属線への菌体付着量は、sucrose入り培地で最も多く、starch入り培地、maltose入り培地では観察されなかった。又、5%sucrose入り培地で一日培養してかすかに金属線への菌体の付着を認めた後、各種糖入り培地で培養した結果、sucrose入り培地で菌体付着量が多く、starchやmaltose入り培地では、コントロールとほぼ同様であった。(4)各種糖入り培地で培養した後の培地のpHは、sucrose入り培地で最も低く、starchやmaltose入り培地のpHはコントロールとほぼ同様であった。これらの結果より、S.mutans菌はstarchやmaltoseを分解する酵素を持たないことが推測できる。Dental plaque, one cause of dental caries and periodontal diseases, is formed by the synthesis of water-insoluble polyglucan by glucosyl transferase possessed by S. mutans. When various sugars infiltrate dental plaque, S. mutans metabolizes them and produces organic acids, consequently decreasing the dental plaque pH, which decalcifies enamel. Of the various sugars, it has not yet been clarified whether maltose decreases the dental plaque pH. Thus, we performed a basic study of bacterial cell body synthesis and organic acid productivity using various sugars. 1) The highest number of bacterial cells adhering to the test tube wall was noted when bacteria were cultured with sucrose-containing medium, whereas no adhesion was noted in cultures with starch-or maltose-containing medium. 2) The highest number of bacterial cells adhering to metal wire was noted in culture with sucrose-containing medium, whereas no adhesion was noted in cultures with starch-or maltose-containing medium. After slight adhesion to metal wire was noted after culture for 1 day with medium containing 5% sucrose, bacteria were subsequently cultured with media containing various sugars. The number of adherent bacterial cells was higher in culture with sucrose-containing medium, whereas those in media containing maltose and starch were similar to that in the medium a containing various sugars, the lowest pH was detected in culture with medium containing maltose, whereas pH values in cultures with starch-and maltose-containing media were similar to that in the control. These findings suggest that S. mutans has no starch- or maltose-metabolic enzyme