口腔链球菌摄取生物素与口内白色念珠菌生长的关系

为了探讨口腔细菌生态平衡机制，本文体外检测了４株口腔链球菌（Ｓ．ｓａｌｉｖａｒｉｕｓ，Ｓ．ｓａｎｇｕｉｓ，Ｓ．ｍｕｔａｎｓ和Ｓ．ｍｉｔｉｏｒ）和白色念珠菌生长对生物素的依赖性。结果显示白色念珠菌和口腔链球菌的生长绝对依赖生物素，前者最大半数生长需要生物素约１０ｐＭｏｌ／Ｌ，其最大生长率所需生物素约为１００ｐＭｏｌ／Ｌ；而后者最大半数生长需生物素为５２５ｐＭｏｌ／Ｌ。正常人血清和唾液中生物素的含量约为２１２２９４ｐＭｏｌ／Ｌ。生物素饥饿状态下的白色念珠菌和口腔链球菌，以及唾液离心沉淀物（绝大多数为细菌）摄取生物素具温度依赖性，而代谢抑制剂（叠氮化合物、氰化物和醋酸碘）和某些抗生素（杆菌肽、短杆菌肽、万古霉素和二性霉素）具选择性抑制效应，提示生物素的摄取和跨膜转运是一依赖能量的主动过程。用唾液沉淀物和口腔链球菌吸收培养基中的生物素或与白色念珠菌共同培养，显著抑制白色念珠菌的生长。本文首次提供实验证据显示口腔优势菌可能通过竞争生物素等营养成份，抑制白色念珠菌生长，以维持口腔微生物之生态平衡。

UPTAKE OF BIOTIN BY ORAL STREPTOCOCCI IMPLICATIONS FOR INTRAORAL GROWTH OF CANDIDA ALBICANS

To investigate the mechanisms of oral microbial ecological balance,we examined the biotin dependent growth of C.albicans,S.salivarius,S.sanguis,S.mutans,and S.mitior.These oranisms were obsolutely biotin-dependent.The maximal growth of C.albicans required biotin concentrations of 100 pMol/L or more,and half maximal growth occured at approximately 10 pMol/L of biotin,whereas the half maximalgrowth of oral streptococci occuring between 5 pMol/L(S.mitior)to 25 pMol/L(S.mutans).Uptake of biotin by all of biotin-deficient organisims tested was temperature-dependent,and selectively inhibitable by metabolic inhibitors(azide,cyanide,Iodoacetate)and certain antibiotics,Bacitracin,Gramicidin,Vancomycin,and Amphotericin B,suggesting active transport of biotin by these organisms.The biotin-dependent growth of C.albicans markedly reduced when co-cultured with oral streptococci or in the medium preincubated with oral bacteria to remove biotin,indicating that the growth inhibition resulted from biotindeficiency,rather than the release of some factors from the salivary organisms.This study provided evidence indicating that oral bacteria competition for biotin may play an important role in the growth inhibition of C.albicans within the healthy oral cavity.