Distinct Mycoplasma pneumoniae Interactions with Sulfated and Sialylated Receptors
Caitlin R Williams1, Li Chen2,3,4, Edward S Sheppard1
1Department of Microbiology, University of Georgia, Athens, Georgia, USA.
Abstract:
Mycoplasma pneumoniae is a cell wall-less bacterial pathogen of the conducting airways, causing bronchitis and atypical or "walking" pneumonia in humans. M. pneumoniae recognizes sialylated and sulfated oligosaccharide receptors to colonize the respiratory tract, but the contribution of the latter is particularly unclear. We used chamber slides coated with sulfatide (3-O-sulfogalactosylceramide) to provide a baseline for M. pneumoniae binding and gliding motility. As expected, M. pneumoniae bound to surfaces coated with sulfatide in a manner that was dependent on sulfatide concentration and incubation temperature and inhibited by competing dextran sulfate. However, mycoplasmas bound to sulfatide exhibited no gliding motility, regardless of receptor density. M. pneumoniae also bound lactose 3'-sulfate ligated to an inert polymer scaffold, and binding was inhibited by competing dextran sulfate. The major adhesin protein P1 mediates adherence to terminal sialic acids linked α-2,3, but P1-specific antibodies that blocked M. pneumoniae hemadsorption (HA) and binding to the sialylated glycoprotein laminin by 95% failed to inhibit mycoplasma binding to sulfatide, suggesting that P1 does not mediate binding to sulfated galactose. Consistent with this conclusion, the M. pneumoniae HA-negative mutant II-3 failed to bind to sialylated receptors but adhered to sulfatide in a temperature-dependent manner.
Insights
Mycoplasma pneumoniae binds to sulfated glycolipids in the respiratory tract. However, this binding does not support the characteristic gliding motility essential for colonization.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Cellular Adhesion
Background:
- Mycoplasma pneumoniae is a significant human respiratory pathogen.
- It colonizes the airways by recognizing sialylated and sulfated oligosaccharide receptors.
- The specific role of sulfated receptors in M. pneumoniae colonization remains unclear.
Purpose of the Study:
- To investigate the role of sulfated oligosaccharides in Mycoplasma pneumoniae binding and motility.
- To determine if the major adhesin P1 mediates binding to sulfated receptors.
Main Methods:
- Utilized chamber slides coated with sulfatide (3-O-sulfogalactosylceramide) and lactose 3'-sulfate.
- Assessed Mycoplasma pneumoniae binding and gliding motility on coated surfaces.
- Employed P1-specific antibodies and an HA-negative mutant (II-3) to differentiate binding mechanisms.
Main Results:
- Mycoplasma pneumoniae demonstrated dose- and temperature-dependent binding to sulfatide and lactose 3'-sulfate.
- Binding to sulfated receptors was inhibited by dextran sulfate.
- Crucially, binding to sulfatide did not result in gliding motility, and P1-specific antibodies did not inhibit this binding.
Conclusions:
- Mycoplasma pneumoniae binds to sulfated galactose-containing glycolipids via a mechanism independent of the P1 adhesin.
- Binding to sulfated receptors does not support the gliding motility necessary for colonization.
- This suggests a distinct role for sulfated receptors in the initial attachment phase, separate from motility-driven colonization.
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