Intercellular signaling is required for developmental gene expression in Myxococcus xanthus

Area of Science:

• Microbiology
• Developmental Biology
• Molecular Genetics

Background:

• Myxococcus xanthus exhibits complex multicellular development.
• Extracellular complementation by wild-type cells is known for certain developmental mutants.
• The genetic basis and molecular mechanisms of this complementation are not fully understood.

Purpose of the Study:

• To investigate extracellular complementation of Myxococcus xanthus A- group developmental mutations.
• To identify the developmental stage affected by A- mutations.
• To characterize the nature of the complementing substance.

Main Methods:

• Utilized Tn5 lac transposon insertions to study developmentally regulated genes.
• Assessed beta-galactosidase expression in A- mutants complemented by wild-type cells.
• Analyzed cell-free washes and conditioned starvation buffer from wild-type and mutant cells.

Main Results:

• A- mutations significantly reduced developmental beta-galactosidase expression from 18 of 21 Tn5 lac insertions.
• Wild-type cells restored beta-galactosidase expression in complemented A- Tn5 lac mutants.
• An extracellular substance released by wild-type cells rescued early developmental gene expression (1.5 hr) and restored normal morphology in A- mutants.

Conclusions:

• A- group mutations in Myxococcus xanthus cause a developmental block between 1-2 hours.
• Wild-type cells secrete an essential factor that rescues developmental gene expression and morphology in A- mutants.
• This finding elucidates a key extracellular signaling mechanism in Myxococcus xanthus development.