'Prokaryotic Genomes' represents a print version of the 'PLoS ONE Prokaryotic Genome Collection'. The collection is an attempt to present and highlight a number of important articles that describe whole genome sequence and/or comparative genomics of important prokaryotic organisms. We believe that this collection will be able to facilitate understanding of the biology and lifestyle of the underlying organisms not only through the content of the Research Articles, but also from the external information sources which are linked to from the original articles. This printed volume will be particularly of interest to the students and teaching communities and the libraries in developing countries where internet access is limited or not affordable as yet. 'Prokaryotic Genomes' is produced in collaboration with CreateSpace and is edited and distributed by Dr Niyaz Ahmed [PLoS ONE Section Editor for Genomics & Microbiology] under the Creative Commons Attribution License. Articles are presented in order of publication date and new articles will be periodically added to the collection. All articles contained in this book are also available online through the PLoS ONE Collections website (http: //www.ploscollections.org/static/poneCollections.action).