title: A comparative proteomic analysis of Vibrio cholerae O1 wild-type cells versus a phoB mutant showed that the PhoB/PhoR system is required for full growth and rpoS expression under inorganic phosphate abundance.
abstract: PhoB/PhoR is a two-component system originally described as involved in inorganic phosphate (Pi) transport and metabolism under Pi limitation. In order to disclose other roles of this system, a proteomic analysis of Vibrio cholerae 569BSR and its phoB/phoR mutant under high Pi levels was performed. Most of the proteins downregulated by the mutant have roles in energy production and conversion and in amino acid transport and metabolism. In contrast, the phoB/phoR mutant upregulated genes mainly involved in adaptation to atypical conditions, indicating that the absence of a functional PhoB/PhoR caused increased expression of a number of genes from distinct stress response pathways. This might be a strategy to overcome the lack of RpoS, whose expression in the stationary phase cells of V. cholerae seems to be controlled by PhoB/PhoR. Moreover, compared to the wild-type strain the phoB/phoR mutant presented a reduced cell density at stationary phase of culture in Pi abundance, lower resistance to acid shock, but higher tolerance to thermal and osmotic stresses. Together our findings show, for the first time, the requirement of PhoB/PhoR for full growth under high Pi level and for the accumulation of RpoS, indicating that PhoB/PhoR is a fundamental system for the biology of V. cholerae.
  
  
  CONCLUSIONS
  Certain V. cholerae strains are pathogenic to humans, causing cholera, an acute dehydrating diarrhoeal disease endemic in Southern Asia, parts of Africa and Latin America, where it has been responsible for significant mortality and economical damage. Its ability to grow within distinct niches is dependent on gene expression regulation. PhoB/PhoR is a two-component system originally described as involved in inorganic phosphate (Pi) transport and metabolism under Pi limitation. However, Pho regulon genes also play roles in virulence, motility and biofilm formation, among others. In this paper we report that the absence of a functional PhoB/PhoR caused increased expression of a number of genes from distinct stress response pathways, in Pi abundance. Moreover, we showed, for the first time, that the interrelationship between PhoB-RpoS-(p)ppGpp-poly(P) in V. cholerae, is somewhat diverse from the model of inter-regulation between those systems, described in Escherichia coli. The V. cholerae dependence on PhoB/PhoR for the RpoS mediated stress response and cellular growth under Pi abundance, suggests that this system's roles are broader than previously thought.
authors.affiliation: Unidade Multidisciplinar de Genômica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil. llery@biof.ufrj.br
authors.forename: Letícia M S
authors.initials: LM
authors.lastname: Lery
authors.forename: Carolina L
authors.initials: CL
authors.lastname: Goulart
authors.forename: Felipe R
authors.initials: FR
authors.lastname: Figueiredo
authors.forename: Karine S
authors.initials: KS
authors.lastname: Verdoorn
authors.forename: Marcelo
authors.initials: M
authors.lastname: Einicker-Lamas
authors.forename: Fabio M
authors.initials: FM
authors.lastname: Gomes
authors.forename: Ednildo A
authors.initials: EA
authors.lastname: Machado
authors.forename: Paulo M
authors.initials: PM
authors.lastname: Bisch
authors.forename: Wanda M A
authors.initials: WM
authors.lastname: von Kruger
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D015536:Down-Regulation; D015964:Gene Expression Regulation, Bacterial; D006150:Guanine Nucleotides / Q000378:metabolism; D009154:Mutation; D010710:Phosphates / Q000378:metabolism*; D011122:Polyphosphates / Q000378:metabolism; D040901:Proteomics; D012808:Sigma Factor / Q000096:biosynthesis; D059467:Transcriptome; D015854:Up-Regulation; D041241:Vibrio cholerae O1 / Q000235:genetics* / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D006150:Guanine Nucleotides; D010710:Phosphates; D011122:Polyphosphates; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; C061278:PhoB protein, Bacteria; C061279:PhoR protein, Bacteria