Abstract
Wall teichoic acid (WTA) or related polyanionic cell wall glycopolymers are produced by most Gram-positive bacterial species and have been implicated in various cellular functions. WTA and the proton gradient across bacterial membranes are known to control the activity of autolysins but the molecular details of these interactions are poorly understood. We demonstrate that WTA contributes substantially to the proton-binding capacity of Staphylococcus aureus cell walls and controls autolysis largely via the major autolysin AtlA whose activity is known to decline at acidic pH values. Compounds that increase or decrease the activity of the respiratory chain, a main source of protons in the cell wall, modulated autolysis rates in WTA-producing cells but did not affect the augmented autolytic activity observed in a WTA-deficient mutant. We propose that WTA represents a cation-exchanger like mesh in the Gram-positive cell envelopes that is required for creating a locally acidified milieu to govern the pH-dependent activity of autolysins.
Highlights
The bacterial cell envelope governs vital processes including maintenance of cell shape, cell division, and protection against environmental challenges
The protonbinding sites in the mutant were 23% reduced compared to the wild type (Table 1), which confirms that Wall teichoic acid (WTA) contributes substantially to the proton-binding capacity of the S. aureus cell envelope
DtagO complemented with a plasmid-encoded copy of tagO had the same proton-binding capacity as the wild type indicating that the difference between wild type and DtagO resulted from its inability to synthesize WTA
Summary
The bacterial cell envelope governs vital processes including maintenance of cell shape, cell division, and protection against environmental challenges. It has a crucial role in the respiratory energy metabolism because the cytoplasmic membrane harbors the electron transport chain components, which generate a proton gradient across the membrane that is used to generate ATP or energize transport processes [1,2]. The cell envelope of B. subtilis cells has been shown to be protonated during respiratory metabolism [7,8] and the polyanionic CWGs have been implicated in cation binding [9,10]. It has remained unclear if the proton-binding capacity of WTA may impact on the pH-sensitive activity of cell wall-associated enzymes such as autolysins
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