Structural and germination defects of Bacillus subtilis spores with altered contents of a spore coat protein

Abstract

The start sites for transcription and translation of a Bacillus subtilis spore coat protein gene, cotT, were determined. The CotT protein was synthesized as a 10.1-kDa precursor which was processed to a coat polypeptide of 7.8 kDa. Insertional inactivation of the cotT gene resulted in spores with an altered appearance of the inner coat layers and slow germination in response to a germination solution containing fructose, glucose, and asparagine. Rates of germination in L-alanine and in Penassay broth were the same as that of the wild type. A strain containing the cotT gene on a low-copy-number plasmid produced spores with an excess of CotT precursor and a thickening of the striated inner coat. These spores responded poorly to all of the germinants mentioned above. A site-directed mutation of the codon at the processing site of CotT resulted in the accumulation of the precursor in sporulating cells and on the spores, but there was no effect on the germination rates or solvent resistance of these spores. Both the lack and the overproduction of CotT led to subtle alterations in the structure of the inner spore coat and in the capacity of spores to respond to particular germinants.