Читать книгу Thermal Food Engineering Operations - NITIN KUMAR - Страница 40

The cell contains some extracellular protein, which warns or senses the probability of danger when there is any environmental stress for instance heat [31]. These processes comprise fluctuations of events of protein and gene expression with the persistence of averting and/or lessening injury to cells. As already discussed, resistance is higher in the stationary phase of growth rather than the exponential one because of the sigma factor [32]. If a bacterium survives, it can exist in a VBNC state. This denotes a state in which the cells cannot be detected by standard culture on enriched agar media, although remaining viable and capable of resuscitation under favorable conditions. VBNC was mainly observed among Gram-negative bacteria and has been proposed as a strategy for survival in natural environments [33]. More than 60 bacterial species are described as being able to enter into a VBNC state, among them Gram-positive (e.g., L. monocytogenes, Enterococcus, Micrococcus luteus) and Gram-negative (e.g., E. coli, Vibrio cholerae, Vibrio vulnificus, Legionella pneumophila, Campylobacter jejuni, Salmonella enterica, Pseudomonas aeruginosa, Helicobacter pylorii) bacteria can be found [34].