Localization and Interactions of Teichoic Acid Synthetic Enzymes inBacillus subtilis

Abstract

The thick wall of gram-positive bacteria is a polymer meshwork composed predominantly of peptidoglycan (PG) and teichoic acids, both of which have a critical function in maintenance of the structural integrity and the shape of the cell. In Bacillus subtilis 168 the major teichoic acid is covalently coupled to PG and is known as wall teichoic acid (WTA). Recently, PG insertion/degradation over the lateral wall has been shown to occur in a helical pattern. However, the spatial organization of WTA assembly and its relationship with cell shape and PG assembly are largely unknown. We have characterized the localization of green fluorescent protein fusions to proteins involved in several steps of WTA synthesis in B. subtilis: TagB In most bacteria, the rigid cell wall (CW) is responsible for providing shape and structural integrity to the cell. The thick CW of gram-positive bacteria is a multilayered structure composed predominantly of peptidoglycan (PG) (also called murein) and anionic polymers, particularly teichoic acids (TA) (for recent reviews, see references 5, 47, and 54). The highly cross-linked PG polymer (poly-N-acetylglucosamine and Nacetylmuramic acid) network is an essential determinant of cell shape and is responsible for protection from the cellular turgor pressure. Many roles for TA have been proposed, including cell shape maintenance (61, 68), resistance to antimicrobial peptides (1, 35, 36), biofilm formation (27), acid tolerance (9) and, efficient release of secreted proteins into the culture medium (49).TA are either covalently bound to the PG (wall TA [WTA]) or anchored to the cytoplasmic membrane (lipo-TA). In the gram-positive model organism Bacillus subtilis, WTA is present in quantities roughly equal to those of PG and constitutes the major class of anionic polymers (26). The type of WTA polymer varies between strains. In B. subtilis 168, the major WTA consists of a poly-glycerol-phosphate [poly-(Gro-P)] chain of 45 to 60 subunits and a "PG linkage unit" of N-acetylglucosamine-␤-(1-4)-N-acetylmannosamine (GlcNAc-ManNAc). WTA is covalently linked to the PG through a phosphodiester bond between the anomeric carbon of GlcNAc in the PG linkage unit and the 6-hydroxyl of MurNAc in the PG chain.In B. subtilis 168 the genes responsible for WTA synthesis are tagABDEFGHO and mnaA (Fig.

Teichoic acids are temporal and spatial regulators of peptidoglycan cross-linking in Staphylococcus aureus

“…Lack of LTA synthesis in rod-shaped Bacillus subtilis cells causes defects in the formation of the division septum and in cell separation (14), whereas lack of WTAs results in round cells (15). Moreover, enzymes involved in LTA synthesis localize predominantly at the division sites of bacteria (14), and enzymes involved in the synthesis of WTAs localize in helical patterns (16) similar to the previously described patterns of PGN synthesis observed during elongation of B. subtilis cells (17). The observation that mutants lacking LTAs have altered autolysis rates (5,18) or that interference with the synthesis of WTA in B. subtilis triggers the transcription of several genes involved in PGN synthesis (19), constitutes additional, indirect evidence that suggests a link between TAs and cell morphogenesis through an effect on the biosynthesis of PGNs, the correct assembly of which is required for proper cell division and morphogenesis.…”

The Sweet Tooth of Bacteria: Common Themes in Bacterial Glycoconjugates

“…WTA plays a role in cell elongation in certain rod-shaped bacteria, as was shown by mutation of WTA, which resulted in a round bacterial morphology instead of a rod in B. subtilis (228). LTA is synthesized at the site of cell division in B. subtilis and is believed to be involved in cell division (229,230).…”

ABC Transporters Involved in Export of Cell Surface Glycoconjugates

“…Group E contains NBD proteins of various lengths. Although some of them contain an extended C-terminal domain, topology predictions indicate that this domain is actually periplasmic and therefore unlikely to be involved in the recognition of teichoic acids for export from the cytoplasm (44). For example, the C-terminal regions of the TagH homologs from Enterococcus faecalis and Lactococcus lactis contain a predicted LysM domain following the transmembrane domain, which could be involved in binding to peptidoglycan, to which wall teichoic acids are covalently linked in the periplasm (117).…”