AN UNUSUALLY SMALL GENE REQUIRED FOR SPORULATION BY BACILLUS-SUBTILIS

We report the cloning and characterization of an unusually small gene called spoVM whose product is required for normal formation of the cor tex and coat during sporulation in Bacillus subtilis. The spoVM gene i s adjacent to, and in convergent orientation with, the B. subtilis hom ologue to the Escherichia coli gene for ribosomal protein L28. The spo VM open reading frame is only 26 codons in length and is capable of en coding a polypeptide of 3 kDa. The short length of spoVM was verified by means of complementation experiments with wild-type and deletion-mu tated copies of the open reading frame and by engineering the synthesi s of the spoVM gene product in E. coli. Transcription of spoVM was ind uced during the second hour of sporulation (approximately stage II) by the appearance of the sporulation RNA polymerase sigma factor, sigma( E). Efficient transcription of spoVM additionally required the action of the sporulation DNA-binding protein SpoIIID. Because spoVM was not strongly required for the transcription of several genes expressed at late times in development, its protein product is likely to play a mor phogenetic rather than a regulatory role in sporulation.