Occurrence of phosphorylserine in the spore coat of Bacillus subtilis NRRL B558

Phosphorylserine was isolated from the spores of Bacillus subtilis NRRL B 558. This phosphorylated amino acid was only found in the spore coat protein and was not detectable in vegetative cells. The compound was characteristically synthesized at a late stage of sporulation and its turnover did not occur until the completion of mature spore formation. The protein which contains phosphorylserine was not solubilized from the spore coat by digestion with pronase or treatment with any detergents.