D-Allose Inhibits Fruiting Body Formation and Sporulation in Myxococcus xanthus

Department of Microbiology, Immunology and Molecular Genetics, and School of Dentistry, University of California, Los Angeles

^* To whom correspondence should be addressed. Email: wenyuan{at}ucla.edu.

	Abstract

Myxococcus xanthus, a gram negative soil bacterium, responds to amino acid starvation by entering a process of multicellular development which culminates in the assembly of spore-filled fruiting bodies. Previous studies utilizing developmental inhibitors (such as methionine, lysine, or threonine) have revealed important clues about the mechanisms involved in fruiting body formation. We used Biolog Phenotype Microarrays^TM to screen 384 chemicals for complete inhibition of fruiting body development in M. xanthus. Here, we report the identification of a novel inhibitor of fruiting body formation and sporulation, D-allose. D-allose, a rare sugar, is a member of the aldohexose family and a C3 epimer of glucose. Our studies show that D-allose does not affect cell growth, viability, agglutination or motility. However, -galactosidase reporters demonstrate that genes activated between 4-14 hrs of development show significantly lower expression levels in the presence of D-allose. Furthermore, inhibition of fruiting body formation occurs only when D-allose is added to submerged cultures before 12 hrs of development. In competition studies, high concentrations of galactose and xylose antagonize the non-fruiting response to D-allose while glucose is capable of partial antagonism. Finally, a magellan-4 transposon mutagenesis screen identified glcK, a putative glucokinase, required for D-allose-mediated inhibition of fruiting body formation. Subsequent glucokinase activity assays of the glcK mutant further supported the role of this protein in glucose phosphorylation.