What is an endospore?

An endospore is a specialized, highly resistant, dormant structure formed within the vegetative cell of some bacteria e.g. Bacillus (rod), Clostridium (rod), Sporosarcina (cocci), Desulfatomaculum under adverse environmental conditions like scarcity of water and nutrients. It was discovered by German Botanist Ferdinand Conn. It is resistant to environment stresses and can survive extreme heat, lack of water and exposure to many toxic chemicals and radiations for years. This resistance is attributed to the presence of calcium dipicolinate, small acid soluble DNA binding proteins, dehydrated protoplast, presence of efficient DNA repair enzymes, spore coat and greater stability of cell proteins.

Structurally, endospore has a complex structure. From outside, it is covered with exosporium - a thin delicate covering. Beneath exosporium, a spore coat lies which consist of several layers of protein and under it is a cortex made up of peptidoglycan. Inside the cortex is a spore cell wall which surrounds the core (protoplast). Core is metabolically active and consists of ribosomes, nucleoid, etc. Endospores are very important clinically and also in food industry because of their resistance to heat and other lethal agents that normally kill vegetative cells. Further, growth of some endospore forming bacteria in foods is a problem as it may produce toxins and lead to diseases.