Biomarkers to Identify and Characterize Small Colony Variants of Escherichia coli K-12
Victor Santos, Anthony W. Paratore, Kanta Dutta, Irvin N. Hirshfield

Abstract
Small colony variants (SCVs) were initially discovered over a century ago, and were characterized morphologically by their small colony size, and convex, smooth appearance. There has been extensive study of Staphylococcus aureus SCVs because of their association with persistent infections such as skin, soft tissue infections, chronic osteomyelitis, and cystic fibrosis. In contrast to the abundance of studies on staphylococci, especially pathogenic S. aureus, relatively little has been investigated in E. coli SCVs although they have been associated with chronic, recurring infections, such as urinary tract infections, and prosthetic hip infections. Three independently isolated E. coli SCVs were investigated in this study; IH3, from pH 3.0 LB medium, IH9 from commercial apple cider (pH 3.7), which is a weak organic acid, and the mutant strain, JW0623, a lipoic acid (lipA) auxotroph obtained from the Keio collection. Neither IH3 nor IH9 was found to be auxotrophic. The strains were grown to log-phase in neutral LB, followed by RTPCR and electrophoretic analysis. Five genes were found to be upregulated in all three strains: fecR, wcaC, wcaK, gadA, and cfa. These genes appear to be good candidates for molecular biomarkers that could be used to identify E. coli SCVs from clinical isolates.

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