engleski

The effects of starvation on Lactobacillus brevis L62 evolution

Stress conditions such as starvation, low pH, oxidative, osmotic stress and temperature variation induce diversity and evolution of lactic acid bacteria in natural environment, during fermentative processes and passing through gastrointestinal tract. During nutrient deprivation bacteria adapt through random spontaneous mutation. Beneficial mutations enable bacterial surviving by activating the alternative metabolic pathways. Thereby, bacteria survive by metabolizing the detritus from dead cells: amino acids, carbohydrates, lipids and DNA. For the present study, the effects of prolonged starvation on protein expression of Lactobacillus brevis L62 were investigated. The cells were grown in batch culture system for prolonged time period. Changes in protein expression between 75-day-old clones and parent cells were detected by two-dimensional gel electrophoresis. The proteins were assigned by MALDI-TOF/TOF analysis enhanced with de novo sequencing that enable unambiguous protein identification. Results showed that proteins engaged in several metabolic pathways such as glycolysis, glycerolipid metabolism and amino acid metabolism are differentially expressed after starvation. The level of produced acetic and lactic acids measured with high-efficiency liquid chromatography showed that 75-day-old clones produce less lactic acid in comparison to parent cells. Based on the data gathered trough amino acid analysis it could be supposed that L. brevis started to metabolize glycine, histidine and arginine during prolonged starvation. Through studying the adaptive bacteria it is possible to understand the evolutionary processes and diversity in natural populations. Better understanding of lactic acid bacteria evolution during prolonged starvation may facilitate new strategies for their development with advantageous characteristics.

Evolution; Lactobacillus brevis; starvation; mass spectrometry

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