Related Experiment Videos
Defects in motility and development of Myxococcus xanthus lipopolysaccharide mutants
1Department of Microbiology, University of Minnesota Medical School, Minneapolis 55455.
Abstract:
Five transposon Tn5 mutants of the procaryote Myxococcus xanthus had been shown previously to be defective in lipopolysaccharide biosynthesis (J. M. Fink,-M. Kalos, and J. F. Zissler, J. Bacteriol. 171:2033-2041, 1989). These mutants were studied for possible defects in gliding motility and multicellular development. Wild-type M. xanthus cells glide both as single cells and as groups of cells. We found that the Tn5 lipopolysaccharide O-antigen mutants were defective in single-cell motility but were unaltered in group motility. These mutant strains were slow to develop but eventually gave rise to normal, spore-filled fruiting bodies. We also had shown previously that 56 (ethyl methanesulfonate-induced and spontaneous) phage-resistant mutants were defective in lipopolysaccharide biosynthesis. We found that many of these lipopolysaccharide O-antigen mutants were defective in single-cell motility but were unaltered in group motility. These mutants also gave rise to normal, spore-filled fruiting bodies. We also studied several phage-resistant mutants which were lacking a side-chain carbohydrate on the lipopolysaccharide core. These mutants possessed both single-cell motility and group motility but were altered in the magnitude of gliding. These mutants were blocked early in development and could not form multicellular fruiting bodies. Several of the mutations in the developmentally aberrant strains were mapped to a single locus by using a collection of genetically linked transposons as genetic markers.
Insights
Lipopolysaccharide O-antigen mutants in Myxococcus xanthus show defects in single-cell gliding motility but retain group motility and normal development. Mutations affecting the lipopolysaccharide core impact motility and block multicellular development.
Area of Science:
- Microbiology
- Bacterial Genetics
- Cellular Motility
Background:
- Myxococcus xanthus is a bacterium known for its unique gliding motility and complex multicellular development.
- Previous studies identified transposon Tn5 and ethyl methanesulfonate-induced mutants defective in lipopolysaccharide (LPS) biosynthesis.
- LPS is a crucial component of the outer membrane in Gram-negative bacteria, influencing cell surface properties.
Purpose of the Study:
- To investigate the role of lipopolysaccharide biosynthesis in Myxococcus xanthus gliding motility and multicellular development.
- To characterize the phenotypes of LPS mutants, specifically O-antigen and core carbohydrate mutants, in relation to their motility and developmental processes.
Main Methods:
- Generation and characterization of Myxococcus xanthus mutants using transposon Tn5 mutagenesis and ethyl methanesulfonate (EMS) treatment.
- Assessing single-cell and group gliding motility of wild-type and mutant strains.
- Observing and quantifying multicellular development, including fruiting body formation and sporulation.
Main Results:
- Transposon Tn5 and EMS-induced mutants with defects in LPS O-antigen biosynthesis exhibited impaired single-cell motility but normal group motility.
- These O-antigen mutants were capable of completing multicellular development, forming normal, spore-filled fruiting bodies.
- Mutants lacking a side-chain carbohydrate on the LPS core displayed altered gliding motility (magnitude) and were blocked early in development, failing to form fruiting bodies.
- Genetic mapping localized several mutations in developmentally aberrant strains to a single genetic locus.
Conclusions:
- Lipopolysaccharide O-antigen is essential for wild-type single-cell gliding motility in Myxococcus xanthus but not for group motility or development.
- Defects in the LPS core structure, specifically the absence of a side-chain carbohydrate, severely impair both gliding motility and multicellular development.
- These findings highlight the critical role of LPS structure in M. xanthus cell surface functions and developmental pathways.