Cell walls of facultative alkaliphilic Bacillus sp. C-125 are composed of peptidoglycan, teichuronic acid, and teichuronopeptide. A mutant lacking teichuronic acid, or defective in both teichuronic acid and teichuronopeptide has been isolated from the organism. We now constructed another type of a cell-wall defective mutant that was defective in teichuronopeptide but had teichuronic acid, by cell fusion using protoplasts prepared from a wild-type strain and a mutant defective in teichuronopeptide and teichuronic acid. This mutant grew more poorly than wild type or a teichuronic acid-defective strain of C-125. The growth, however, was faster than that of the parental strain defective in both teichuronic acid and teichuronopeptide.