Cell wall modifications during osmotic stress in Lactobacillus casei

• Published in: Journal of applied microbiology 2005-01, Vol.98 (1), p.84-95
• Main Authors: Piuri, M., Sanchez‐Rivas, C., Ruzal, S.M.
• Format: Article
• Language: English
• Subjects: Bacteriological Techniques; Cell Wall - chemistry; Cell Wall - ultrastructure; Drug Resistance; Electrophoresis, Polyacrylamide Gel; Hydrolysis; Lactobacillus casei; Lactobacillus casei - chemistry; Lactobacillus casei - physiology; Lactobacillus casei - ultrastructure; Microscopy, Electron; Osmosis; osmotic stress; PBP; Penicillin-Binding Proteins - analysis; peptidoglycan; Peptidoglycan - analysis
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2004.02428.x

Aims:  To study the modification of the cell wall of Lactobacillus casei ATCC 393 grown in high salt conditions. Methods and Results:  Differences in the overall structure of cell wall between growth in high salt (MRS + 1 mol l−1 NaCl; N condition) and control (MRS; C condition) conditions were determined by transmission electronic microscopy and analytical procedures. Lactobacillus casei cells grown in N condition were significantly larger than cells grown under unstressed C condition. Increased sensitivity to mutanolysin and antibiotics with target in the cell wall was observed in N condition. Purified cell wall also showed the increased sensitivity to lysis by mutanolysin. Analysis of peptidoglycan (PG) from stressed cells showed that modification was at the structural level in accordance with a decreased PG cross‐link involving penicillin‐binding proteins (PBP). Nine PBP were first described in this species and these proteins were expressed in low percentages or presented a modified pattern of saturation with penicillin G (Pen G) during growth in high salt. Three of the essential PBP were fully saturated in N condition at lower Pen G concentrations than in C condition, suggesting differences in functionality in vivo. Conclusions:  The results show that growth in high salt modified the structural properties of the cell wall. Significance and Impact of Study:  Advances in understanding the adaptation to high osmolarity, in particular those involving sensitivity to lysis of lactic acid bacteria.