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 M 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 downregulation 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.

The Myxobacterium Myxococcus xanthus Can Sense and Respond to the Quorum Signals Secreted by Potential Prey Organisms

“…Myxococcus xanthus wild-type strain DK1622 ( Kaiser, 1979 ) was used throughout, maintained on the rich medium DCY as described previously ( Whitworth et al, 2008 ), with incubation at 30°C. Low nutrient DCY/10 medium is DCY diluted to 10% v/v.…”

“…Media were solidified with the addition of 1.5% agar. TM was used as a nutrient free medium for developmental assays ( Whitworth et al, 2008 ). E. coli strain TOP10 (Invitrogen) and B. megaterium (strain NCIMB 4821) were cultivated on LB ( Sambrook et al, 1989 ), solidified with 1.5% agar as required.…”

Myxobacterial Genomics and Post-Genomics: A Review of Genome Biology, Genome Sequences and Related ‘Omics Studies

“…Prior to the advent of genome sequencing, transcription was normally assayed in M. xanthus using northern blots or reporter genes. Typically, a promoterless lacZ gene would be cloned downstream of a promoter and introduced into the chromosome (typically at the attB site), with production of LacZ (measured by colorimetric assays) indicating transcriptional activity (e.g., [ 108 ]). Alternatively, a promoterless lacZ within the transposon Tn 5 lac allowed transcription to be assessed wherever a transposon had inserted into the chromosome [ 109 ].…”

Myxococcus xanthus Pph2 Is a Manganese-dependent Protein Phosphatase Involved in Energy Metabolism

“…xanthus (15), which have not been associated to any specific protein, so far. Hence, Whitworth et al (16) suggested that those phosphatase activities could be originated by specific PPs. Until now, only Pph1 has been characterized (17).…”