To be used as a model in dental research, an animal must fulfil experimental needs and information on the composition and variation of its oral flora must be available. Only limited data are available on the indigenous oral bacterial flora of BALB/c mice. In this work, a total of 671 isolates from different sites (saliva, tongue, teeth, and mucosa) of the oral cavity of BALB/c mice were identified. Only 18 different species were isolated, which indicates the relative simplicity of the flora. The predominant species of the total cultivable flora were "Lactobacillus murinus" (38%), Staphylococcus aureus (37%), Streptococcus faecalis (8%), Staphylococcus sciuri (4%), and Escherichia coli (3%). The other species each represent less than 2% of the flora. "Lactobacillus murinus" is found in greater proportion on mucosa than in the other sites, Staph. aureus predominates in saliva, and Strep. faecalis was found in greater proportion in tooth samples. Statistical analyses, using the minimum percentage of similarity, indicate that there is some variation among the microflora of different mice but that this difference is smaller for mice from the same lot. These results set the basis for the study of the variations of the indigenous oral microflora of BALB/c mice under different conditions.

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ABSTRACT. COL product~on in aerobic bacteria was modeled from the time-courses of the 1x1 vitl-o activity of isocitrate dehydrogenase (IDH), bacterial protein, and the concentrat~on of the carbon source in the cultures. The model was based on the concept of bisubstrate control of the IDH reaction throughout the exponential, steady-state, and senescent phases of the cultures In the exponential phase, the measured rates of CO, production and the In vltro IDH actlvity were closely coupled, but in the senescent phase, they became uncoupled The In vltro IDH actlvity remained hlgh even after the culture's carbon source was exhausted, while the CO, production fell to low levels Based on the hypothesis that thls uncoupling was caused by ~n t e r n a l substrate limitation, 2 mathematical models incorporating a bisubstrate enzyme kinetics algorithm were constructed and tested. The models predicted the rate of CO2 production throughout the different phases of the cultures w~t h a n r2 greater than 0.84.

~a g a c e~, Sylvie ~o y~, Lily S t-~r n a n d~, Jean-Pierre ~a~n e~

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