BACILLUS-SUBTILIS POSSESSES A 2ND DETERMINANT WITH EXTENSIVE SEQUENCESIMILARITY TO THE ESCHERICHIA-COLI-MREB MORPHOGENE

A gene with substantial sequence similarity to the mreB morphogene of Bacillus subtilis has been identified at 302 degrees on the chromosoma l map by A, Decatur, B, Kunkel, and R. Losick (Harvard University; per sonal communication). Our characterization has revealed that the prote in product of this determinant (termed mbl for mreB-like) is 55 and 53 % identical in sequence to the MreB proteins of B. subtilis and Escher ichia coli, respectively, The protein is 86% identical to a protein id entified as MreB from Bacillus cereus, suggesting that the B, cereus p rotein is actually Mbl. Insertional inactivation of mbl indicated that this gene is not essential for cell viability or sporulation, Cells b earing mutant mbl alleles display a decreased growth rate and an alter ed cellular morphology. The cells appear bloated and are frequently tw isted, Intergenic suppressor mutations which restore the growth rate t o an approximately normal level arise within the mutant population. A second site mutation, designated som-1, was mapped to the hisA-mbl reg ion of the chromosome by transduction.