**1. Introduction**

Biofilms are the aggregation of microbial cells, which are associated with the surface in almost an irreversible manner, i.e. cannot be removed by gently rising [1]. They are attached with a biotic or abiotic surface integrated into the matrix that they have produced [2]. An accustomed biofilm provides favorable conditions for genetic material mobility between the cells and has a defined architecture. It is also reported that these surface-associated microorganisms possess definite phenotype with reference to growth rate and gene transcription [1].

The credit of discovery of microbial biofilm can be given to Van Leeuwenhoek who, with his simple microscope first observed the microorganisms on tooth surface [1].
