We report Western blot data showing that the 42.8-kDa product of the previo
usly characterized cotH locus (8) is a structural component of the Bacillus
subtilis spore coat. We show that the assembly of CotH requires both CotE
and GerE. In agreement,vith these observations, the ultrastructural analysi
s of purified spores suggests that CotH is needed for proper formation of b
oth inner and outer layers of the coat.