Cadmium (Cd) in soil represents a direct contact risk to both humans and ecological recipients due to its high toxicity and ready uptake by plants [ 1, 2].
Through acquisition of novel genes, the recipient cell may change its ecological preference and the process could promote speciation.
In bacterial pathogens, recombination leads to shuffling of virulence genes and can confer new ecological niches on recipient bacteria [ 94, 95].
Horizontal gene transfer (HGT) is postulated to play an important role in evolution because sometimes the transferred genes allow the recipient to adapt to new ecological niches (e.g.: [ 1- 4]).
Horizontal transfer events are generally a result of the proximity of donor and recipient lineages inhabiting the same ecological niche, with genetic material being transferred over short physical distances [ 8] without regard to domain boundaries.
Conversely, gene knockout strategies have produced strains with reduced ecological fitness as recipients for genetic engineering to improve virulence; the resulting strains are hypervirulent, but will not persist in the environment.
It is also often seen that a horizontally transferred gene provides the recipient organism better compatibility with its ecological environment.
Horizontal gene transfer plays an important role in evolution because it sometimes allows recipient lineages to adapt to new ecological niches.
The mechanisms for HTs remain obscure, although these transfer events require the occurrence of common premises, such as geographical, temporal, and ecological overlap between donor and recipient species.
From the examples discussed above it is clear that some of the laterally acquired genes have the ability to increase the metabolic diversity of recipient bacteria enabling them to explore new ecological niches.
Through the acquisition of new genes and functions, the recipient organism can accelerate evolution and adapt to new ecological niches [ 1, 2].
