Bacterial Strategies to Preserve Cell Wall Integrity Against Environmental Threats

Abstract

Bacterial cells are surrounded by an exoskeleton-like structure, the cell wall, composed primarily of the peptidoglycan (PG) sacculus. This structure is made up of glycan strands cross-linked by short peptides generating a covalent mesh that shapes bacteria and prevents their lysis due to their high internal osmotic pressure. Even though the PG is virtually universal in bacteria, there is a notable degree of diversity in its chemical structure. Modifications in both the sugars and peptides are known to be instrumental for bacteria to cope with diverse environmental challenges. In this review, we summarize and discuss the cell wall strategies to withstand biotic and abiotic environmental insults such as the effect of antibiotics targeting cell wall enzymes, predatory PG hydrolytic proteins, and PG signaling systems. Finally we will discuss the opportunities that species-specific PG variability might open to develop antimicrobial therapies.

Paraprobiotics and Postbiotics of Probiotic Lactobacilli, Their Positive Effects on the Host and Action Mechanisms: A Review

“…The cell wall of Lactobacilli contains a thick peptidoglycan layer, which is a multilayer, cross-linked glycan chain with a repeating pentapeptide unit of β-1,4-linked N-acetylglucosamine and N-acetylmuramic disaccharide units (107) and the fundamental composition of the glycan strands and pentapeptides was strainspecific for Lactobacilli (108). At the time of biosynthesis, assembly, and incorporation of peptidoglycan components, modifications happen in the bacterial peptidoglycan which could enhance the sensitivity to autolysis, hydrophobicity of the cell envelope, and resistance to lysozyme (109). Peptidoglycan of Lactobacillus casei (L. casei), Lactobacillus johnsonii (L. johnsonii) JCM 2012 and Lactobacillus plantarum ATCC 14917 was reported to suppress interleukin-12 (IL-12) production via Toll-like receptor 2 (TLR2) which have been associated with autoimmune and inflammatory bowel diseases (94).…”

Peptidoglycan editing provides immunity to Acinetobacter baumannii during bacterial warfare

“…These modifications can occur during PG precursor synthesis or after PG precursors are incorporated into the growing cell wall meshwork (14). PG modifications enabling immune evasion and resistance to antibiotics have been extensively studied and generally include chemical modifications to the glycan backbone or changes in pentapeptide composition or degree of cross-linking (12,(14)(15)(16)(17)(18). In addition, PG editing with noncanonical d-amino acids (NCDAAs) has been shown to make bacteria more resistant to osmotic stress (19).…”

Constructing and deconstructing the bacterial cell wall

“…As the chemical entities that comprise the bacterial cell envelopes-the peptidoglycan (similar structurally in both Gram-positive and Gram-negative bacteria), the Gram-positive wall teichoic acid, and the Gramnegative lipopolysaccharide-each lack eukaryotic counterparts, antibiotics that target their synthesis have intrinsic selectivity and hence generally safety. 49,[72][73][74] The integrity of these cell envelopes rests not on any one of these entities, but on their seamless integration. Wright opined that we have entered a golden age of understanding as to how antibiotics function.…”