Hydric stress

The growth at osmolalities larger than 33 mosm does not enhance the recovery of bacteria dried in absence of sugar (data not shown). Thus, it is unlikely that L. bulgaricus can accumulate osmolites to face hydric stress in the culture, or that its accumulation is insufficient to protect the bacteria from the stress produced by drying at high temperatures. 

Dehydration factors may affect cells by different mechanisms. However, in all of them it is possible to adapt cells to the hydric stress by growing them in media of high osmolalify. In fhe case of L. bulgaricus, it cannot accumulate osmolites. Hence, the presence of protectant compounds in the dehydration process is vital to preserve the structure of protein and membranes. 

Survival under freezing temperatures or hydric stress... 

From these arguments, we may conclude that trehalose is the best compromise to maintain an artificial H-bond network that temporarily replaces that developed by H2O molecules and avoids both those catastrophic consequences, that is the formation upon freezing of crystalline ice in that part outside macromolecules that is in contact with liquid water, and the collapse of the structure of membranes or of secondary structures of proteins upon drying due to the escape of H2O molecules. This artificial H-bond network is much less flexible than that established by H2O molecules and considerably slows down the dynamics of H2O molecules (23, 28). It consequently does not allow normal activity. It does not allow life to proceed in the same way as in the H2O network of living conditions. It nevertheless avoids irreversible transformation of the structure of the macromolecule by hydric stress, thus allowing resumption of living activities by rehydration. The discussion that has appeared in the literature to decide which mechanism is the most important, the glass... 

High temperatures in this case do not positively affect sugar accumulation, if a considerable hydric stress exists. In the opposite case, they can limit this accumulation by favoring vegetative vine growth when the water supply is not limited. 

Wetlands are usually defined by hydric soils, the presence of vegetation adapted to wet conditions, and hydrology. There are several definitions of wetlands, each stressing different characteristics and wetland values. 

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