lipoteichoic

Lipoteichoic acids (LTA) are anionic polymers found in the cell envelopes of most Gram-positive bacteria. They consist primarily of glycerol phosphate repeats anchored to the cytoplasmic membrane by a glycolipid tail. The polymer extends through the peptidoglycan layer and appears on the external surface of the cell. In some species, the repeating units can be ribitol phosphate or mixed backbones, and the chain length and degree of substitution vary.

LTAs are distinct from wall teichoic acids (WTA). While LTAs are anchored in the membrane via a glycolipid primer and project outward, WTAs are covalently attached to peptidoglycan within the cell wall. The lipid anchor of LTA and the composition of the repeating units can differ among taxa, contributing to species-specific surface chemistry.

Biosynthesis of LTA involves a set of enzymes that assemble glycerophosphate units onto a membrane-anchored primer, typically a glycolipid, followed by processing and export to the cell surface. A key enzyme family includes lipoteichoic acid synthases that polymerize the glycerolphosphate chain. The exact pathways and components can vary among Gram-positive bacteria.

Functions attributed to LTA include maintenance of cell envelope architecture, regulation of autolysins and cell division, and binding of divalent cations, which helps preserve charge balance and integrity of the cell surface. LTAs also influence interactions with the host during infection, where they can be recognized by the innate immune system, particularly Toll-like receptor 2-containing complexes, contributing to inflammatory responses. Modifications to LTA can alter its immunogenic properties.

In research and medicine, LTAs are of interest as potential antimicrobial targets, vaccine components, or diagnostic markers, though variability among species and essentiality limits broad applicability.