Molecular biology is not only a story of complex molecules, machines and processes but also of massive information flow via a variety of molecular messages. And while information flow is often associated with the DNA macromolecule, there are less celebrated but ubiquitous armies of molecular machines that are busy attaching, modifying and removing small chemical tags to and from both DNA and proteins. It is a massive information network and these chemical tags—such as methyl, hydroxyl and phosphate groups—act as a sort of molecular modifier or barcode regulating a diverse array of cellular functions. Another molecular barcode is the acetyl group, long thought to be mainly at work in eukaryotes, has now found to be important in bacteria as well. It is, as one evolutionist put it, the “dawning of a new age.” Read more