| Abstract [eng] |
Enteric bacteria often encounter acid stress conditions in a variety of pathogenic and natural situations. Bacteria that are able to survive under such conditions have to endure a pH difference of 4-5 pH units either by secreting the excess of protons or blocking extracellular protons from the cytoplasm. As a result bacteria have evolved complex strategies designed to detect, adapt and minimize acid induced damages. It is thought that cell envelope is one of the main structures determining protection from the acid stress, though its structural and functional components involved in the protection and the maintenance of homeostasis are not known. The aim of this study was to analyze changes of the cell envelope permeability to protons and the buffering power of bacterial suspensions during acid adaptation. We also investigated hypothetical acid stress protein Asr for its chaperone like activity. E. coli mutants of structural membrane components (ompC and phoE) and a periplasmic acid stress protein (Asr) were used in the studies. We showed, that envelope permeability to protons and cells buffering capacity increase during acid adaptation and the level of changes depends on the external pH. OmpC porin is essential for increasing E. coli cells buffering capacity while anion-specific PhoE porin has no influence on cell envelope interaction with protons. In vitro studies with periplasmic protein aggregation led to a conclusion that periplasmic protein Asr is not an acid stress chaperone and its role in cell resistance to acid is still to be determined. |
