In unfavorable circumstances, some bacteria
belonging to Bacillus, Clostridium genera
(Firmicute phylum, mostly Gram-positive) enters into a metabolically dormant
state i.e. Endospores 1. They are tough multi-layered cellular structures
formed, as a means of survival. The structure of spore includes i) Exosporium
(absent in Bacillus subtilis), thin covering
surrounding the spore coat; ii) Spore coat; iii) Cortex, beneath the spore coat
and rich in peptidoglycan; iv) Core wall, beneath the cortex and surrounds the
core; v) Core contains the spore chromosomal DNA in association with
chromatin-like proteins known as SASPs (small acid-soluble spore proteins),
that have role in the protection of spore DNA from UV radiation and heat 1, 2,
3. All these structural components of spores contribute for the resistance of
spores to heat, radiation and chemicals 2. The proteins in the outermost
spore layers (coat and exosporium) play an important role in stress resistance
of spores to various chemical and environmental agents. They restrict the entry
of the exogenous chemicals to the spore core and also can detoxify the chemical
agents by reacting with them. In addition to the structural framework, yet
another barrier to killing is the core water content which is much lower than
that in dividing cell protoplast 3. Low water content along with core
proteins (e.g. SASPs) and dipicolinic acid provides spore resistance to wet and
dry heat, respectively 4, 6. UV and gamma-radiation can damages DNA are
potentially lethal to spores. UV irradiation of spores generates the
thymidyl-thymidine adduct termed spore photoproduct; these lesions can be
repaired by repair systems present in the spore 5, 6, 7. Some of the spores
can be highly resistant and can even survive in the space where there is no
atmosphere and high background radiation 8. Despite they are toughest to kill
still they can be killed by using various chemical or physical agents that can
directly damages DNA or the protective spore membrane. Bacteriophage is another
option that can be used to kill the gram positive spores 9. Spores are one of
the major present day problems facing by health and food industry 10;
therefore there is an urgent need in the advancement of the methods to
eliminate spores.

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