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Abstract:
Myxococcus xanthus is a model bacterium to study social behavior. At the
cellular level, the different social behaviors of M. xanthus involve
extensive cell-cell contacts. Here, we used bioinformatics, genetics,
heterologous expression and biochemical experiments to identify and
characterize the key enzymes in M. xanthus implicated in O-antigen and
lipopolysaccharide (LPS) biosynthesis and examined the role of LPS
O-antigen in M. xanthus social behaviors. We identified WbaP(Mx)
(MXAN_2922) as the polyisoprenyl-phosphate hexose-1-phosphate
transferase responsible for priming O-antigen synthesis. In heterologous
expression experiments, WbaP(Mx) complemented a Salmonella enterica
mutant lacking the endogenous WbaP that primes O-antigen synthesis,
indicating that WbaP(Mx) transfers galactose-1-P to
undecaprenyl-phosphate. We also identified WaaL(Mx) (MXAN_2919), as the
O-antigen ligase that joins O-antigen to lipid A-core. Our data also
support the previous suggestion that Wzm(Mx) (MXAN_4622) and Wzt(Mx)
(MXAN_4623) form the Wzm/Wzt ABC transporter. We show that mutations
that block different steps in LPS O-antigen synthesis can cause
pleiotropic phenotypes. Also, using a wbaP(Mx) deletion mutant, we
revisited the role of LPS O-antigen and demonstrate that it is important
for gliding motility, conditionally important for type IV pili-dependent
motility and required to complete the developmental program leading to
the formation of spore-filled fruiting bodies.
