However, it is well known that the bac-teria isolated from polluted environment are tolerant to higher concentrations of metals than those isolated from unpolluted areas. Further, after the addition of metals, metal tolerance is in-creased in bacterial communities by the death of sensitive species and subsequent competition and adaptation of surviving bacteria Currently, the interactions between endophytes and hyperaccumulator plants have attracted the atten-tion of several investigators due to biotechnological applications for bioremediation and for studying the composition of bacterial communities living on a naturally contaminated environment. In general, the hyperac-cumulating plants accumulate huge amounts of heavy metals and can therefore provide a specific environment for bacterial endo-phytes that could be adapted to survive in high metal concentra-tions. For instance, the metal resistant endophytic bacteria have been isolated from various hyperaccu-mulating plants such as Alyssum bertolonii, Thlaspicaerulescens, Thl-aspi goesingense and Nicotiana tabacum . As shown in Table 1, the hyperaccumulating plants can be colonized simultaneously by a high number of different divisions, genera, and species of metal resistant endophytic bacteria. The variation in bacteria that has been reported as endophytes spans a signifi-cant range of Gram-positive and Gram-negative bacteria.