title: Phosphate acquisition components of the Myxococcus xanthus Pho regulon are regulated by both phosphate availability and development.
abstract: In many organisms, phosphatase expression and phosphate (P) uptake are coordinately regulated by the Pho regulon. In Myxococcus xanthus P limitation initiates multicellular development, a process associated with changes in phosphatase expression. We sought here to characterize the link between P acquisition and development in this bacterium, an organism capable of preying upon other microorganisms as a sole nutrient source. M. xanthus seems to possess no significant internal P stores, as reducing the P concentration to less than 10 microM retarded growth within one doubling time. Pyrophosphate, polyphosphate, and glyceraldehyde-3-phosphate could support growth as sole P sources, although many other P-containing biomolecules could not (including nucleic acids and phospholipids). Several Pho regulon promoters were found to be highly active during vegetative growth, and P limitation specifically induced pstSCAB, AcPA1, and pho3 promoter activity and repressed pit expression. Enhanced pstSCAB and pho3 promoter activities in a phoP4 mutant (in the presence of high and low concentrations of P) suggested that PhoP4 acts as a repressor of these genes. However, in a phoP4 background, the activities of pstSCAB remained P regulated, suggesting that there is additional regulation by a P-sensitive factor. Initiation of multicellular development caused immediate down-regulation of Pho regulon genes and caused pstSCAB and pho3 promoter activities to become P insensitive. Hence, P acquisition components of the M. xanthus Pho regulon are regulated by both P availability and development, with developmental down-regulation overriding up-regulation by P limitation. These observations suggest that when development is initiated, subsequent changes in P availability become irrelevant to the population, which presumably has sufficient intrinsic P to ensure completion of the developmental program.
authors.affiliation: Institute of Biological Sciences, Cledwyn Building, Aberystwyth University, Ceredigion SY23 3DD, United Kingdom. dew@aber.ac.uk
authors.forename: David E
authors.initials: DE
authors.lastname: Whitworth
authors.forename: Antony B
authors.initials: AB
authors.lastname: Holmes
authors.forename: Alistair G
authors.initials: AG
authors.lastname: Irvine
authors.forename: David A
authors.initials: DA
authors.lastname: Hodgson
authors.forename: David J
authors.initials: DJ
authors.lastname: Scanlan
mesh_terms: D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D007700:Kinetics; D016941:Myxococcus xanthus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism* / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D018085:Regulon / Q000235:genetics*
chemical_list: D010710:Phosphates