Shewanella baltica Ecotypes Have Wide Transcriptional Variation under the Same Growth Conditions

Abstract

Eukaryotic studies have shown considerable transcriptional variation among individuals from the same population. It has been suggested that natural variation in eukaryotic gene expression may have significant evolutionary consequences and may explain large-scale phenotypic divergence of closely related species, such as humans and chimpanzees (M.-C. King and A. C. Wilson, Science 188:107–116, 1975, http://dx.doi.org/10.1126/science.1090005 ; M. F. Oleksiak, G. A. Churchill, and D. L. Crawford, Nat Genet 32:261–266, 2002, http://dx.doi.org/10.1038/ng983 ). However, natural variation in gene expression is much less well understood in prokaryotic organisms. In this study, we used four sequenced strains of the marine bacterium Shewanella baltica to better understand the natural transcriptional divergence of a stratified prokaryotic population. We found substantial low-magnitude expressional variation among the four S. baltica strains cultivated under identical laboratory conditions. Collectively, our results indicate that transcriptional variation is an important factor for ecological speciation.