A simple and random genome deletion method combining insertion sequence (IS) element IS31831 and the Cre/loxP excision system generated 42 Corynebacterium glutamicum mutants (0.2-186 kb). A total of 393.6 kb (11.9% of C. glutamicum R genome) coding for 331 genes was confirmed to be nonessential under standard laboratory conditions. The deletion strains, generated using only two vectors, varied not only in their lengths but also the location of the deletion along the C. glutamicum R genome. By comparing and analyzing the generated deletion strains, identification of nonessential genes, the roles of genes of hitherto unknown function, and gene-gene interactions can be easily and efficiently determined.