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Induction of the Pho regulon suppresses the growth defect of an Escherichia coli sgrS mutant, connecting phosphate metabolism to the glucose-phosphate stress response.

ABSTRACT: Some bacteria experience stress when glucose-6-phosphate or analogues like ?-methyl glucoside-6-phosphate (?MG6P) accumulate in the cell. In Escherichia coli, the small SgrS RNA is vital to recovery from glucose-phosphate stress; the growth of sgrS mutants is strongly inhibited by ?MG. SgrS helps to restore growth in part through inhibiting translation of the ptsG mRNA, which encodes the major glucose transporter EIICB(Glc). While the regulatory mechanism of SgrS has been characterized, little is known about how glucose-phosphate stress connects to other aspects of cell physiology. In the present study, we discovered that mutation of pitA, which encodes the low-affinity transporter of inorganic phosphate, partially suppresses the ?MG growth defect of an sgrS mutant. Induction of the stress response was also reduced in the sgrS pitA mutant compared to its sgrS parent. Microarray analysis suggested that expression of phosphate (Pho) regulon genes is increased in the sgrS pitA mutant compared to the sgrS parent. Consistent with this, we found increased PhoA (alkaline phosphatase) activity in the sgrS pitA mutant compared to the sgrS strain. Further, direct induction of the Pho regulon (in a pitA(+) background) also resulted in partial suppression of the sgrS growth defect. The suppression was reversed when Pho induction was prevented by mutation of phoB, which encodes the Pho transcriptional activator. Deletion of individual Pho structural genes in suppressed strains did not identify a single gene responsible for suppression. Altogether, this work describes one of the first studies of glucose-phosphate stress physiology and suggests a novel connection of carbon and phosphate metabolism.

SUBMITTER: Richards GR

PROVIDER: S-EPMC3347205 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Induction of the Pho regulon suppresses the growth defect of an Escherichia coli sgrS mutant, connecting phosphate metabolism to the glucose-phosphate stress response.

Richards Gregory R GR Vanderpool Carin K CK

Journal of bacteriology 20120316 10

Some bacteria experience stress when glucose-6-phosphate or analogues like α-methyl glucoside-6-phosphate (αMG6P) accumulate in the cell. In Escherichia coli, the small SgrS RNA is vital to recovery from glucose-phosphate stress; the growth of sgrS mutants is strongly inhibited by αMG. SgrS helps to restore growth in part through inhibiting translation of the ptsG mRNA, which encodes the major glucose transporter EIICB(Glc). While the regulatory mechanism of SgrS has been characterized, little i ...[more]

PMID: 22427626

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Project description:The phosphate-specific transport operon, pstSCAB-phoU, of Gram-negative bacteria is an essential part of the Pho regulon. Its key roles are to encode a high-affinity inorganic phosphate transport system and to prevent activation of PhoB in phosphate-rich environments. In general, mutations in pstSCAB-phoU lead to the constitutive expression of the Pho regulon. Previously, we constructed a pstCA deletion mutant of Citrobacter rodentium and found it to be attenuated for virulence in mice, its natural host. This attenuation was dependent on PhoB or PhoB-regulated gene(s) because a phoB mutation restored virulence for mice to the pstCA mutant. To investigate how downstream genes may contribute to the virulence of C. rodentium, we used microarray analysis to investigate global gene expression of C. rodentium strain ICC169 and its isogenic pstCA mutant when grown in phosphate-rich medium. Overall 323 genes of the pstCA mutant were differentially expressed by at least 1.5-fold compared to the wild-type C. rodentium. Of these 145 were up-regulated and 178 were down-regulated. Differentially expressed genes included some involved in phosphate homoeostasis, cellular metabolism and protein metabolism. A large number of genes involved in stress responses and of unknown function were also differentially expressed, as were some virulence-associated genes. Up-regulated virulence-associated genes in the pstCA mutant included that for DegP, a serine protease, which appeared to be directly regulated by PhoB. Down-regulated genes included those for the production of the urease, flagella, NleG8 (a type III-secreted protein) and the tad focus (which encodes type IVb pili in Yersinia enterocolitica). Infection studies using C57/BL6 mice showed that DegP and NleG8 play a role in bacterial virulence. Overall, our study provides evidence that Pho is a global regulator of gene expression in C. rodentium and indicates the presence of at least two previously unrecognized virulence determinants of C. rodentium, namely, DegP and NleG8.

Project description:Most currently used antibiotics originate from Streptomycetes and phosphate limitation is an important trigger of their biosynthesis. Understanding the molecular processes underpinning such regulation is of crucial importance to exploit the great metabolic diversity of these bacteria and get a better understanding of the role of these molecules in the physiology of the producing bacteria. To contribute to this field, a comparative proteomic analysis of two closely related model strains, Streptomyces lividans and Streptomyces coelicolor was carried out. These strains possess identical biosynthetic pathways directing the synthesis of three well-characterized antibiotics (CDA, RED and ACT) but only S. coelicolor expresses them at a high level. Previous studies established that the antibiotic producer, S. coelicolor, is characterized by an oxidative metabolism and a reduced triacylglycerol content compared to the none producer, S. lividans, characterized by a glycolytic metabolism. Our proteomic data support these findings and reveal that these drastically different metabolic features could, at least in part, due to the weaker abundance of proteins of the two component system PhoR/PhoP in S. coelicolor compared to S. lividans. In condition of phosphate limitation, PhoR/PhoP is known to control positively and negatively, respectively, phosphate and nitrogen assimilation and our study revealed that it might also control the expression of some genes of central carbon metabolism. The tuning down of the regulatory role of PhoR/PhoP in S. coelicolor is thus expected to be correlated with low and high phosphate and nitrogen availability, respectively and with changes in central carbon metabolic features. These changes are likely to be responsible for the observed differences between S. coelicolor and S. lividans concerning energetic metabolism, triacylglycerol biosynthesis and antibiotic production. Furthermore, a novel view of the contribution of the bio-active molecules produced in this context, to the regulation of the energetic metabolism of the producing bacteria, is proposed and discussed.

Project description:Background: The UK horticultural and agricultural industries routinely apply large amounts of inorganic fertiliser to maintain crop yield and quality, since chemical assays of soil nutrients are unreliable. Excessive fertiliser applications are costly and can lead to unnecessary pollution. A possible solution is to use sensor (GM or non-GM) technologies that exploit the changes in plant gene expression under incipient nutrient deficiency. Aim: The aim of this project is to use mutants with reduced leaf phosphate contents to identify genes upregulated in response to phosphate stress. Preliminary gene expression analysis has identified several phosphate responsive genes to be upregulated in the pho1 mutant. However, further replicates of the experiment are required to confirm these changes. Methods: Arabidopsis mutant pho1 (N8507) and its parent ecotype Columbia 2 (N907) will be grown on MS agar under identical conditions. RNA will be extracted from the rosette leaves of both parent and mutant and the same growth stage. By comparing the expression profiles, we will be able to differentiate between genes that are upregulated in leaves experiencing phosphate stress. Previously, two GeneChips have been used (mutant and parent) to provide preliminary data. A further two biological replicates are now required to confirm these results. Promoters and transcripts of these genes will underpin the development of novel sensor technologies, and knowledge of the gene expression profiles will improve our understanding of the physiology of plant mineral nutrition. Experimenter name = John Hammond Experimenter phone = 01789 470382 Experimenter fax = 01789 470552 Experimenter address = Plant Sciences Division Experimenter address = School of Biosciences Experimenter address = University of Nottingham Experimenter address = Sutton Bonington Campus Experimenter address = Loughborough Experimenter zip/postal_code = LE12 5RD Experimenter country = UK Keywords: genetic_modification_design

Dataset Information

Induction of the Pho regulon suppresses the growth defect of an Escherichia coli sgrS mutant, connecting phosphate metabolism to the glucose-phosphate stress response.

Publications

Induction of the Pho regulon suppresses the growth defect of an Escherichia coli sgrS mutant, connecting phosphate metabolism to the glucose-phosphate stress response.

Similar Datasets

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