DNA sulfur modification: 

It began with an easily overlooked DNA degradation (Dnd) phenomenon during electrophoresis and eventually led to the discovery of an unprecedented DNA sulfur modification governed by five dnd genes. This unusual DNA modification, called phosphorothioation, is the first physiological modification identified on the DNA backbone, in which the non-bridging oxygen is replaced by sulfur in a sequence-selective and stereo-specific manner. Homologous dnd gene clusters have been identified in diverse and distantly related bacteria and thus have drawn immediate attention of the entire microbial scientific community. Chemical, genetic, enzymatic, bio-informatical and analytical aspects of this novel post-replicative DNA modification have been performed. The physiological functions of the DNA phosphorothioate modification in bacteria are comprehensively under investigation.