Abstract
Lipoteichoic acid (LTA) is an important cell wall polymer in Gram-positive bacteria and often consists a polyglycerolphosphate backbone chain that is linked to the membrane by a glycolipid. In Listeria monocytogenes this glycolipid is Gal-Glc-DAG or Gal-Ptd-6Glc-DAG. Using a bioinformatics approach, we have identified L. monocytogenes genes predicted to be involved in glycolipid (lmo2555 and lmo2554) and LTA backbone (lmo0644 and lmo0927) synthesis. LTA and glycolipid analysis of wild-type and mutant strains confirmed the function of Lmo2555 and Lmo2554 as glycosyltransferases required for the formation of Glc-DAG and Gal-Glc-DAG. Deletion of a third gene, lmo2553, located in the same operon resulted in the production of LTA with an altered structure. lmo0927 and lmo0644 encode proteins with high similarity to the staphylococcal LTA synthase LtaS, which is responsible for polyglycerolphosphate backbone synthesis. We show that both proteins are involved in LTA synthesis. Our data support a model whereby Lmo0644 acts as an LTA primase LtaP and transfers the initial glycerolphosphate onto the glycolipid anchor, and Lmo0927 functions as LTA synthase LtaS, which extends the glycerolphosphate backbone chain. Inactivation of LtaS leads to severe growth and cell division defects, underscoring the pivotal role of LTA in this Gram-positive pathogen.
Highlights
The cell wall envelope of Gram-positive bacteria has been an area of active research for decades
The same and two subsequent studies on S. aureus and B. subtilis revealed that Lipoteichoic acid (LTA) is important for normal growth and observed morphological alterations indicate a crucial role of LTA in the cell division
Using a combination of molecular biology and mass spectrometry approaches to characterize glycolipids and LTA synthesized in wild-type and mutant strains, we show that the previously uncharacterized L. monocytogenes genes lmo2555 and lmo2554 encode glycolipid synthesis enzymes, and renamed them LafA and LafB for LTA anchor formation proteins A and B
Summary
The cell wall envelope of Gram-positive bacteria has been an area of active research for decades. By studying its Accepted 27 July, 2009. The recent identification of enzymes responsible for glycolipid and LTA backbone synthesis allowed a phenotypic characterization of strains that are deficient in LTA synthesis or produce LTA of an altered structure. The enzyme responsible for polyglycerolphosphate backbone chain formation has been discovered recently in S. aureus and named LtaS for LTA synthase (Gründling and Schneewind, 2007a). The same and two subsequent studies on S. aureus and B. subtilis revealed that LTA is important for normal growth and observed morphological alterations indicate a crucial role of LTA in the cell division
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