In the aquatic ecosystems, microorganisms are exposed to seasonal and circadian cycles. Abiotic factors (e.g. low temperature, nutrient deprivation) can cause morphological and physiological changes in bacteria, thereby facilitating cell survival. While representing the interface between the cells and external environment, the cell envelope plays a major role in bacterial response to stress and characterization of the changes it undergoes can help to understand the adaptation process. In this study, analysis of the morphological and physiological changes as well as variations in protein composition of the Escherichia coli cell envelope was carried out for populations maintained for 21 days under nutrient deprivation and suboptimal temperatures (4°C and 20°C). It was found that the absence of nutrients led to a temperature-dependent reduction of cell culturability but had no effect on cell viability and integrity. The concentration of membrane proteins playing the key roles in cellular transport, maintenance of cell structure or bioenergetics processes remained mainly unchanged. In contrast, the level of several proteins such as the elongation factor EFTu 1, components of Bam complex or proteins implicated in chemotaxis was altered, thus indicating that cells were readily responding and adapting to stress.
Part of the book: Escherichia coli