1. Micro injection.
2. Methods for gene transfer:
a. The bacterium is treated with divalent cation such as calcium which makes the bacterial cell competent to take up DNA (the pores bacterial cell wail is widened).
The recombinant DNA is forced in to the cell by incubating cells with recombined DNA on ice followed by heat shock (42YC) and then back on ice. This helps the bacteria to take up recombined DNA.
b. High velocity micro particles of gold or tungsten is coated with DNA & bombarded into the cell. This method is called biolistics or gene gun.