In 1997, the complete genomic DNA sequence of Bacillus subtilis (4.2 Mbp) was determined and 4100 genes were identified [Kunst, Ogasawara, Moszer, Albertini, Alloni, Azevedo, Bertero, Bessieres, Bolotin, Borchert, S. et al. (1997) Nature 90, 249-256]. In addition, B. subtilis, which shows an excellent ability to secrete proteins (enzymes) and antibiotics in large quantities outside the cell, plays an important role in industrial and medical fields. It is necessary to clarify the genes involved in the production of compounds by understanding the network of these 4100 genes and the proceeding analysis of genes of unknown functions. In promoting such a study, it is expected that the regulatory system of B. subtilis can be simplified by the creation of a Bacillus strain with a reduced genome by discriminating genes unnecessary for the production of proteins from essential genes, and deleting as many of these unnecessary genes as possible, which may help to understand this complex network of genes. We have previously distinguished essential and non-essential genes by evaluating the growth and enzyme-producing properties of strains of B. subtilis in which about 3000 genes (except 271 essential genes) have been disrupted or deleted singly, and have successfully utilized the findings from these studies in creating the MGIM strain with an approx. I Mbp deletion by serially deleting 17 unnecessary regions from the genome. This strain showed slightly reduced growth in enzyme-production medium, but no marked morphological changes. Moreover, we confirmed that the MGIM strain had cellulase and protease productivity comparable with that of the B. subtilis 168 strain, thus demonstrating that genome reduction does not contribute to a negative influence on enzyme productivity.
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