Cell wall modifications during osmotic stress in Lactobacillus casei

Abstract

M . P I U R I , C . S A N C H E Z -R I V A S A N D S . M . R U Z A L . 2004.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.

Ubiquinone accumulation improves osmotic-stress tolerance in Escherichia coli

“…Quantitative studies indicated, however, that the amounts of compatible solutes produced by E. coli may not be sufficient to maintain cell turgor exclusively based on increasing intracellular osmolality, implying accompanying effects such as molecular crowding 14 . Besides adjusting intracellular osmolality, other bacteria have been shown to modify their cell wall structure upon osmotic stress 5 , but this mechanism has not been observed in E. coli. Virtually all known osmoprotection mechanisms in E. coli therefore relate to the modulation of intracellular osmolality.…”

“…The consequences are changing cellular volume and turgor pressure that exert strong mechanical forces on the cytoplasmic membrane and associated proteins and, if too high, preclude growth of the bacterium and eventually cause cell death 1 . To cope with osmotic stress, bacteria evolved several strategies such as adapting their intracellular osmolality [2][3][4] or increasing their cell wall stability 5 , allowing them to grow in a broad range of solute concentrations.…”

Role of anionic phospholipids in the adaptation of Bacillus subtilis to high salinity

“…We have been studying for several years the biochemical and biophysical characteristics of the cell envelopes of cells grown under osmotic stress both in B. subtilis and in Lactobacillus casei (Ló pez et al, , 2001(Ló pez et al, , 2002Piuri et al, 2003;Machado et al, 2004;Piuri et al, 2005). In these studies, the analysis of membrane lipids has revealed that there is a significant increase in the anionic lipid fraction such as phosphatidylglycerol (PG) and especially cardiolipin (CL) when B. subtilis cells are grown in LB medium containing 1?5 M NaCl.…”

Study of the Relationship between Changes in Lactic Acid Bacterial Cell Components and Stimulation of IL-12 Production under Salt-Stressed Conditions

“…In previous studies, significant enlargement of cells under high ionic stress was observed in Lactobacillus casei 15) and Staphylococcus aureus. 16) To investigate the relationship between salt-stressed culture conditions and cell size, bacterial cell sizes were measured by a particle size analyzer, SALD-2200.…”

“…13) It is well-known that bacterial cell sizes are increased when they are grown in complex media containing high concentrations of NaCl. [14][15][16] The enlargement of cell size is due to a decrease in peptidoglycan cross-links in the cell wall. There have been a few studies on the influence of cell components (cell wall and cell plasma fraction) on the LAB stimulating immune system.…”