The constancy of global regulation across a species: the concentrations of ppGpp and RpoS are strain-specific in Escherichia coli

BMC Microbiology

Research Article

Heloisa Filus Galbiati¹  Beny Spira¹  Thomas Ferenci²  Katherine Phan²  Thu Betteridge² 

[1] Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brazil;School of Molecular and Microbial Biosciences, The University of Sydney, 2006, NSW, Australia;

关键词: Sigma Factor;    Carbon Starvation;    Amino Acid Starvation;    Strain MG1655;    rpoS Gene;   

DOI  :  10.1186/1471-2180-11-62

 received in 2011-01-19, accepted in 2011-03-25,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundSigma factors and the alarmone ppGpp control the allocation of RNA polymerase to promoters under stressful conditions. Both ppGpp and the sigma factor σS (RpoS) are potentially subject to variability across the species Escherichia coli. To find out the extent of strain variation we measured the level of RpoS and ppGpp using 31 E. coli strains from the ECOR collection and one reference K-12 strain.ResultsNine ECORs had highly deleterious mutations in rpoS, 12 had RpoS protein up to 7-fold above that of the reference strain MG1655 and the remainder had comparable or lower levels. Strain variation was also evident in ppGpp accumulation under carbon starvation and spoT mutations were present in several low-ppGpp strains. Three relationships between RpoS and ppGpp levels were found: isolates with zero RpoS but various ppGpp levels, strains where RpoS levels were proportional to ppGpp and a third unexpected class in which RpoS was present but not proportional to ppGpp concentration. High-RpoS and high-ppGpp strains accumulated rpoS mutations under nutrient limitation, providing a source of polymorphisms.ConclusionsThe ppGpp and σS variance means that the expression of genes involved in translation, stress and other traits affected by ppGpp and/or RpoS are likely to be strain-specific and suggest that influential components of regulatory networks are frequently reset by microevolution. Different strains of E. coli have different relationships between ppGpp and RpoS levels and only some exhibit a proportionality between increasing ppGpp and RpoS levels as demonstrated for E. coli K-12.

【 授权许可】

Unknown   
© Ferenci et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.