The action that joins DNA segments and bacteria is transformation. This process involves the uptake of exogenous genetic material (like a DNA segment) by a bacterial cell, leading to the integration of this new genetic material into the bacterial genome.

Here's a breakdown of the process:

1. Donor DNA: The DNA segment (often a plasmid or a fragment of chromosomal DNA) comes from a donor cell.

2. Competency: The bacterial cell must be competent to take up the DNA. This means it has specific proteins on its surface that allow it to bind and internalize the DNA.

3. Uptake: The bacterial cell takes up the donor DNA through its cell membrane.

4. Integration: The donor DNA integrates into the bacterial genome, either by homologous recombination (replacing a similar sequence) or non-homologous recombination (inserting into a different location).

Transformation is a crucial mechanism for horizontal gene transfer in bacteria, allowing them to acquire new traits like antibiotic resistance or the ability to produce toxins.

Let me know if you would like to know more about the process or the different types of transformation!