RESUMEN
A comparative study of DNA homology among 12 strains of thermophilic streptococci currently used as ferments in the dairy industry in different regions of the CIS and 16 strains of mesophilic lactococci obtained from different sources was performed by the method of optical reassociation in solution. These strains were found to form three groups with DNA homology generally not exceeding 30-35% between each other. These data indicate that strains commonly classified as Streptococcus thermophilus may belong to different taxa. At the same time, the DNA base composition was similar in all these strains (the G + C content was 38-40 mol %). Among 16 strains of mesophilic lactococci DNA homology was generally higher than 50%, i.e., all these strains indeed belong to the same species, Lactococcus lactis.
Asunto(s)
ADN Bacteriano/genética , Lactococcus/genética , Homología de Secuencia de Ácido Nucleico , Productos Lácteos , Industria de Alimentos , Especificidad de la EspecieRESUMEN
The antagonistic activity of 9 strains of the genus Lactobacillus with respect to 25 H. pylori clinical cultures was studied with the use of the original method of ring blocks. The presence of high antagonistic activity of strains L. casei 925, L. plantarum 8 RA-3, L. fermentum BL-96 and L. 90265 was established. The newly developed method of the determination of antagonistic activity with respect to H. pylori, taking into account the biological features of this organism, was found to be convenient for work, precise and giving reproducible results.