Under carbohydrate starvation stress, we investigated the generation of non-culturable forms of three bacteriocin (nisin) producing Lactococcus lactis subsp. lactis strains: MSU, 729, and F-116. Inoculum was used in two separate ways: A) cells that have not been washed with culture fluids, B) cells that have been washed twice with regular 0.9% saline. For both types of inoculum, the total number of cells was 0.6 1.0108 cells/ml. Within the first 1-5 days of incubation, populations obtained with type A inoculum showed active growth (up to 2.4109 cells/ml), whereas those acquired with type B inoculum did not proliferate. Micro colonies appeared in the Type B population of MSU strain due to phenotypic dissociation. After then, active growth phase (up to 5.2109 cells/ml) was observed. During the entire experiment, Type B cultures of strains 729 and F-116 did not develop. It was discovered that the type A population changed into non-culturability more quickly than the type B population. This is owing to the fact that these populations have different metabolic strategies and stress sensitivity. Culturability reduced by 3 orders of magnitude for type B (5 orders for type B population of strain MSU) and 6 orders of magnitude for type A population after a year of incubation (383 days). The type A population of strains 729 and F-116 also showed a significant drop in cell size. Bacteriocin activity studies revealed that cells from the type B population were up to 78 times more prolific than those from type A cultures. This phenomena can be explained by changes in population survival strategies that benefit from the antibacterial properties of bacteriocins.
Author (S) Details
Yury D. Pakhomov
Mechnikov Research Institute for Vaccines and Sera, Moscow, Russia.
Larisa P. Blinkova
Mechnikov Research Institute for Vaccines and Sera, Moscow, Russia.
Olga V. Dmitrieva
Mechnikov Research Institute for Vaccines and Sera, Moscow, Russia.
Olga S. Berdyugina
Mechnikov Research Institute for Vaccines and Sera, Moscow, Russia.
Lidia G. Stoyanova
Moscow State University, Faculty of Biology, Department of Microbiology, Russia
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