Table 1 Main strategies of response of bifidobacteria to different stress factors
Stress source | Strategy of response | Molecular mechanisms/players |
|---|---|---|
Heat shock | Proper protein folding | Molecular chaperones: GroEL, GroES, GrpE, DnaJ, DnaK, ClpB, Hsp20 |
Degradation of misfolded proteins | Proteases: ClpC, ClpP | |
Regulatory network | Transcriptional regulators: HrcA, HspR, ClgR | |
Acid pH | Proton extrusion | F1F0-ATPase |
Cytoplasm buffering/ammonia production | Branched-chain amino acid production | |
Glutamine synthetase | ||
Unknown | CysD, MetE | |
Bile salts | Bile salt/acid detoxification | Multidrug transporters and bile efflux pumps (BetA, Ctr) |
Bile salt deconjugation (unclear) | Bile salt hydrolase | |
Alteration of cell surface | Production of extracellular exopolysaccharides | |
Changes in fatty acid composition | ||
Changes in surface-associated proteins: enolase, oligopeptide binding proteins | ||
Changes in energetic metabolism | Increase in ATP synthesis | |
Changes in the ratios of final glycolytic products | ||
Modification of redox status | Methionine synthetase? Peroxidase? | |
Proper protein folding | Molecular chaperones: ClpB, HtrA, GrpE, GroES, GroEL, DnaK | |
Degradation of misfolded proteins | Proteases: ClpC | |
Antimicrobials | Cytoplasm detoxification | Efflux pumps |
Carbon source fluctuations | Ability of degrading a high range of carbohydrates | Extracellular oligosaccharide-binding proteins, glycosydases and transcriptional regulators |