RESUMO
AIMS: The effect of probiotic lactobacilli is likely dependent on the indigenous Lactobacillus strains in the intestinal tract. Since a substantial number of probiotic studies is performed in rodents, we compared the Lactobacillus strains of different rat and mouse populations in three animal facilities. METHODS AND RESULTS: SDS-PAGE and 16S rDNA analysis of cultured faecal lactobacilli revealed that different Lactobacillus strains were detected in genetically similar Wistar rats bred at different locations. Further, within the same animal facility host genetics did not affect the types of the predominant lactobacilli strains. CONCLUSIONS: Our results show that the environmental background of laboratory animals rather than host genetics determines the indigenous Lactobacillus strains that are found. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings underline the importance of microflora analysis in probiotic studies.
Assuntos
Animais de Laboratório , Fezes/microbiologia , Lactobacillus/classificação , Lactobacillus/isolamento & purificação , Animais , Animais de Laboratório/genética , Cruzamento , DNA Ribossômico/análise , Eletroforese em Gel de Poliacrilamida , Abrigo para Animais , Lactobacillus/genética , Camundongos , Filogenia , Probióticos , RNA Ribossômico 16S/genética , Ratos , Ratos WistarRESUMO
A dipeptidase was purified to homogeneity from a crude cell extract of Streptococcus cremoris Wg2 by DEAE-Sephacel column chromatography followed by preparative disc gel electrophoresis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single protein band with a molecular weight of 49,000. The dipeptidase is capable of hydrolyzing a range of dipeptides, but not peptides with longer chains. The enzyme was shown to be a metallo-Mn enzyme with a pH optimum of 8 and a temperature optimum of 50 degrees C. The enzyme is strongly inhibited by thiol-reducing reagents but not by sulfhydryl reagents. Kinetic studies indicated that the enzyme has a relatively low affinity for leucyl-leucine and alanyl-alanine (K(m), 1.6 and 7.9 mM, respectively) but can hydrolyze these substrates at very high rates (V(max), 3,700 and 13,000 mumol/min per mg of protein, respectively).
