الفهرس 
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Abstract
Antibiotics are among the most widely prescribed
drugs in both human and veterinary medicine.
Furthermore, they are used to protect plants against
bacterial and fungal diseases, to decontaminate the
shells of eggs, and to improve weight gain and feed
conversion in a variety of animals. More antibiotics, in
addition, have been essential tools in the elucidation
of specific cellular functions. Nowadays, antibiotics
have a considerable role in genetic engineering.
Antibiotics are low molecular weight microbial
metabolites that, at low concentration, inhibit the
growth or even destroy other microorganisms. The term
low molecular weight substances refers to molecules of
at most a few thousand daltons.
The term antibiosis was coined by Paul Vuillem in
in 1889 and was used by him in a broad sense, referring
to all instances where one species destroys the life of
another to preserve or”maintain its own.