Abstract
As persistent residents of planktonic bacterial cultures, small colony variants (SCVs) constitute a slow-growing subpopulation with atypical colony morphology and unusual biochemical characteristics that, in the case of clinical isolates, cause latent and recurrent infections. We propose a novel blueprint for the formation of E. coli SCVs through DNA microarray analysis, coupled with complete genome sequencing and verification by qRT-PCR. While others have used DNA microarrays to study quorum sensing in E. coli SCVs, our work represents the first proposal for a combination of novel mutations, amplified by a differential shift in expression of select gene groups that work in concert to establish and maintain the SCV phenotype. This combination of genetic and expression events fall under selective pressure, leading to unequal fitness in our strain, SCV IH9 versus its parental strain, BW7261 (a MG1655 descendant). We hypothesize that this combination of events would ordinarily be lethal for bacteria, but instead confers a survival advantage to SCV IH9 due to its slow growth and resistance to acidic and oxidative stress challenges.
Highlights
Resistance to environmental stresses is the paradigm of evolutionary fitness in the microbial world
Small colony variants of Escherichia coli that are typically auxotrophic arise due metabolic gene mutations that result in the emergence of a sub-population of bacteria characterized by reduced colony size and distinct biochemical properties
Our previous work identified a small colony variant of BW25113 strain of Escherichia coli. This small colony variant is auxotrophic for lipoic acid, an important cofactor needed for aerobic cellular respiration and the proper production of adenosine triphosphate (ATP)
Summary
Resistance to environmental stresses is the paradigm of evolutionary fitness in the microbial world. SCVs defective in hemin and menadione synthesis are classified as electron transport defective SCVs due to their hindered production of ATP as a result of said mutation [12] This lack of adequate energy production accounts for their reduced colony size and unique biochemical properties such as acid resistance. Small colony variants of Escherichia coli that are typically auxotrophic arise due metabolic gene mutations that result in the emergence of a sub-population of bacteria characterized by reduced colony size and distinct biochemical properties. Our previous work identified a small colony variant (lipA) of BW25113 strain of Escherichia coli This small colony variant is auxotrophic for lipoic acid, an important cofactor needed for aerobic cellular respiration and the proper production of adenosine triphosphate (ATP). Our discussion will focus on the evolutionary importance of genome-wide differential gene expression of an E. coli SCV
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