Adaptive mutations in the pst operon of Escherichia coli

• Grant number: 13/19307-9
• Support Opportunities: Regular Research Grants
• Start date: February 01, 2014
• End date: July 31, 2016
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal Investigator: Beny Spira
• Grantee: Beny Spira
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

According to the neo-Darwinian synthesis mutations are random events that can be selected and fixed if they confer on the organism a beneficial trait. I.e., natural selection filters pre-existent mutations selecting those that bestow on the organism an adaptive advantage. However, new evidences gathered in the last 25 years suggest the existence of a mutation type that does not obey the known pattern of natural selection, the so called "adaptive mutations". Studies done with bacteria show that the adaptive mutations are associated with non-lethal phenotypes and appear to be directly influenced by environmental conditions. The mechanism of selection of adaptive mutations is not clear, been vigorously debated by the scientific community.The PHO regulon is composed by genes that respond to phosphate (Pi) limitation. The pst operon (pstSCAB-phoU) belongs to the PHO regulon and encodes a high affinity Pi-transport system. On top of that, the Pst system also represses the PHO regulon genes under conditions of of high Pi in the medium. Escherichia coli is unable to use glycerol-2-phosphate (G2P) as a carbon source under excess Pi because hte PHO regulon is repressed under these conditions. Under these condtions, G2P provides a selective pressure on PHO repression, resulting in PHO-constitutive mutations. Most PHO-constitutive mutants reside in the pst operon. Preliminary results in our laboratory indicated that these mutants are of the adaptive kind.In the present project the mechanism of selection of PHO-constitutive mutants will be investigated. The mutations will be identified and sequenced. The adaptive nature of these mutations will also be tested and cellular factors that might have an effect on these mutations, such as the Ugp transport system and RpoS will be evaluated.We have also observed that some PHO-constitutive mutants are unstable and segregate secondary non-constitutive mutants. We would like to shed a light on the mechanism of selection of PHO constitutive mutants and to learn more about the role of pst on the regulation of the PHO regulon. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

NEVES, HENRIQUE IGLESIAS; PEREIRA, TUANNY FERNANDA; YAGIL, EZRA; SPIRA, BENY. Ugp and PitA Participate in the Selection of PHO-Constitutive Mutants. Journal of Bacteriology, v. 197, n. 8, p. 1378-1385, APR 2015. (13/19307-9)