Bacillus subtilis systems biology: Applications of -omics techniques to the study of endospore formation

The principal B. subtilis laboratory strain, strain 168, is derived from a parent strain isolated in Marburg, Germany, following a mutagenesis procedure (1). The popularity of this strain arose after it was shown to be competent for genetic transformation (2, 3), which paved the way for myriad molecular genetics analyses that led to a detailed understanding of the biology of B. subtilis and related Gram-positive bacteria. It is therefore not surprising that strain 168 was the first Gram-positive species to have its entire genome sequenced, at a time when sequencing was a laborious and expensive process. The project to sequence the genome was set up in 1987 by a consortium of over 30 laboratories and took about 10 years to complete. Each laboratory was assigned a different region of the chromosome and used their own cloning and sequencing strategies to manage their assigned portion of the genome (4). The final genome sequence contained 4,214,810 base pairs, and the original annotation included 4,100 protein-coding genes (5). Following the development of sequencing technologies that were considerably faster and more efficient, the genome of B. subtilis strain 168 was resequenced and cleared of sequencing errors in 2009 (6). The most recent update of the annotation brought the total of protein-coding genes to 4,458 (7).