 The study found that genes with a highly biased codon composition and characterizing a functional core in Escarichia coli k12 showed to be periodically distributed along the arcs, suggesting an encoded three-dimensional genomic organization helping functional activities among which are translation and, possibly, transcription. Additionally, functional classes of genes were also shown to systematically organize into two independent positional gene networks, one driven by metabolic genes and the other genes involved in cellular processing and signaling. These findings suggest that functional reasons may explain why genes are periodically organized within the chromosome. Furthermore, this study used a single genome analysis to generate new questions about the evolutionary pressures imposed on the chromosome. This article was authored by Anthony Maffolier and Alessandra Cobain.