What is bacterial spore?

Bacterial spores are highly resistant, dormant structures (i.e. no metabolic activity) formed in response to adverse environmental conditions. They help in the survival of the organisms during adverse environmental conditions; they do not have a role in reproduction.

Spore formation (sporulation) occurs when nutrients, such as sources of carbon and nitrogen are depleted. Bacterial spores are highly resistant to

Heat
Dehydration
Radiation and
Chemicals.

Structure of Bacterial Spore:
An endospore is structurally and chemically more complex than the vegetative cell. It contains more layers than vegetative cells. The resistance of Bacterial spore may be mediated by dipicolinic acid, a calcium ion chelator found only in spores. When the favorable condition prevail, (i.e. availability of water, appropriate nutrients) spores germination occurs which forms vegetative cells of pathogenic bacteria.