title: Role of polyphosphate in thermophilic Synechococcus sp. from microbial mats.
abstract: Synechococcus OS-B', a thermophilic unicellular cyanobacterium, recently isolated from the microbial mats in Octopus Spring (Yellowstone National Park), induces a suite of genes, including phosphatases and transporters, in response to phosphorus (P) starvation. Here we describe two different approaches to examine the ability of Synechococcus OS-B' to synthesize and break down polyphosphate (poly P), a key storage compound in many prokaryotes. First, we developed a transformation protocol to create mutants in the polyphosphate kinase (ppk), the major enzyme responsible for the synthesis of poly P. The ppk mutant exhibited a pleiotropic phenotype with defects in poly P accumulation, aberrant levels of Pho regulon transcripts, growth defects, and changes in cell size and exopolysaccharide levels, among others. Second, we measured transcripts of ppk and ppx (encoding the polyphosphatase) directly from mat samples and found that the levels varied dramatically over a diel cycle. We also used Western blot analysis to quantify levels of PPK and PPX and found that these enzymes differentially accumulated during the diel cycle. Levels of polyphosphate kinase peaked at night, while polyphosphatase levels were highest during the early morning hours. We hypothesize that the opposing activities of these two enzymes allow cells to store and utilize poly P to optimize growth over a diel cycle.
authors.affiliation: Carnegie Institution for Science, Department of Plant Biology, Stanford University, Stanford, California, USA. rosario.gomezgarcia@gmail.com
authors.forename: Maria R
authors.initials: MR
authors.lastname: Gomez-Garcia
authors.forename: Fariba
authors.initials: F
authors.lastname: Fazeli
authors.forename: Alexandra
authors.initials: A
authors.lastname: Grote
authors.forename: Arthur R
authors.initials: AR
authors.lastname: Grossman
authors.forename: Devaki
authors.initials: D
authors.lastname: Bhaya
mesh_terms: D015153:Blotting, Western; D017353:Gene Deletion; D020869:Gene Expression Profiling; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000235:genetics / Q000378:metabolism; D011122:Polyphosphates / Q000378:metabolism*; D046940:Synechococcus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D011122:Polyphosphates; D017856:Phosphotransferases (Phosphate Group Acceptor); C022424:polyphosphate kinase; D010749:Phosphoprotein Phosphatases; C080406:protein phosphatase 4