Mutations in E. coli that affect the phosphate uptake and expression of the PHO regulon genes

• Grant number: 15/13568-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2015
• End date: October 31, 2016
• Field of knowledge: Biological Sciences - Microbiology - Biology and Physiology of Microorganisms
• Principal Investigator: Beny Spira
• Grantee: Raffaele Stasi
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The PHO regulon is a genes and operons complex that respond to the stimulus of phosphate (Pi) limitation. The activation of the PHO genes is mediated by the two component system PhoB-PhoR, along with the proteins that make the Pst transport system. PhoR is the sensor protein that receives the Pi availability signal in the environment and signalize to PhoB, that will activate the transcription of the PHO regulon genes. The Pst system acts like a repressor of PHO, when the concentration of Pi in the environment is high. Mutations in any of the Pst operon genes causes the constitutive expression of the whole PHO regulon. It was constructed in our lab a triple mutant pitA ugpBAEC pstSCAB-phoU, that, theoretically, should not grow in Pi as the only phosphorous source, because it does not contain the two main Pi transporters (PitA and PstSCAB) and also it dos not have the glycerol-phosphate transport system UgpBAEC. The genomic sequencing of this mutant revealed that it carries an 8 bp deletion in the gene phnE, involved in the transport of phosphonates. This kind of mutation had already been described and it is known that it activates the Phn system which is cryptic in E. coli K-12. In this project, we will establish if the deletion in phnE is really the mutation which allows the bacteria to grow in Pi on absence of the others transporters. Besides, it will be also tested the hypothesis that the creC gene allele, which its product phosphorilates PhoB, in absence of PhoR, is responsible for the variables in the regulon PHO genes expression levels.