Why spore cells are very resistant and ineffective against most of the disinfectants?

Microbial cells are basically of two types, vegetative cells and spore cells. Vegetative cells are actively growing cells of microorganisms under favourable conditions. But conditions are not always favourable for microorganisms. Some microorganisms under unfavourable conditions (non availability of food, temperature etc.) transformed in to spore cells. Not all microbes are spore forming but some bacteria like bacillus and clostridium are spore forming bacteria and in case of fungus A.brasiliensis is spore forming. Spore cells are the dormant form of microorganisms in which metabolic activities are reduced. Water content is very low in spore cells. Spore cells have very thick outer coat. This coat is mainly composed of calcium and pectin which provide resistant to these cells. But when these spore cells get favourable conditions again they converted in to the vegetative cells and grow actively. Most of general disinfectants like alcohols are ineffective against spore cells. Outer coat of these spore cells are very hard and impermeable to disinfectants that's why some disinfectants like alcohol can't penetrate inside these spore cells and not able to kill spores. Sporocidal disinfectants are used to kill spore cells. These sporocidal disinfectants penetrate inside the spore cells and easily kill these cell.

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