Secondary metabolism is a term for pathways and small molecule products of metabolism that are not absolutely required for the survival of the organism. These molecules are produced by specific cells, that do not need these metabolites by themselves, but rather can be beneficiary for the whole organism. Secondary metabolites (SMs) are natural products synthesized mainly by bacteria, fungi and plants. They are molecules of low molecular weight with diverse chemical structures and biological activities. The name secondary metabolite originates from the initial observation that their production is not necessary for the growth and reproduction of organisms, in contrast to primary metabolites which include lipids, amino acids, carbohydrates and nucleic acids. However, SMs are far from being secondary and the term “specialized metabolites” is emerging to describe them. It is now accepted that SMs play key roles in the survival of the organisms that produce them because SMs determine interactions within their environment.  The antibiotics are defined as "the complex chemical substances, the secondary metabolites which are produced by microorganisms and act against other microorganisms". Those microorganisms which have capacity to produce more antibiotics can survive for longer time than the others producing antibiotics in less amount.