[Changes in the phase variant spectra in the populations of lactic acid bacteria under antibiotic treatment].

Effect of the antibiotics kanamycin and ampicillin on growth and phase variation of the populations of four strains of lactic acid bacteria (Lactobacillus sp. M67AT, L. casei MB, Enterococcus faecium M, and E.

[Divergence in the level of DNA hybridization and formation of sibling species in the lactic acid bacteria Streptococcus thermophilus].

Previously, five distinct groups with 80-90% intragroup DNA homology values were revealed among 19 lactic acid-producing bacterial strains. The study of 39 new strains of thermophilic streptococci in the present work allowed us to reveal the sixth DNA homology group. The nine strains of this group are similar, at 55-70% DNA homology levels, to the type strain S.

[Repeated immune response in gnotobiotic rats].

Repeated immune response to diphtheria toxoid was investigated in monocontaminated rats. It was shown that repeated immunization of these animals led to a sufficiently intensive immune response by the secondary type, but it ended much earlier than in the usual animals (by the 12th day). A supposition is put forward that earlier termination of the secondary response in gnotobionts is caused by the absence in their lymph nodes of an additional differentiation of cell-precursors at the late periods of secondary immune response.

[Characteristics of the immunomorphological substrate in secondary immunization as dependent on the functional state of the hypothalamic nuclei].

The authors traced the morphological and serological shifts occurring in secondary immunological response against the background of destruction of the posterior hypothalamic nuclei. It was revealed in experiments on rabbits that in primary and secondary immunization carried out against the background of bilateral coagulation of the posterior hypothalamic nucleus the secondary immunological response was reduced in comparison with control. Depression occurred both on account of reduction of the number of cells-precursors, and in connection with disturbances of differentiation of the antibody-forming cells.