A multi-stage experiment was conducted with two different species: a nonpathogenic strain of Buttiauxella agrestis (Ba) and a strain of Haemophilus influenzae (Hi) carrying a plasmid with a virulence gene (Hi/pVir). The cultures were treated as described for each stage (1-5, below), then inoculated into healthy mice. The mice were observed 24 hours later.
1. When Ba was inoculated ---> the mice lived
2. When Hi/pVir was inoculated ---> the mice died
3. When heat-killed Hi/pVir was inoculated ---> the mice lived
4. When Hi/pVir was mixed with Ba, the mixed cells were incubated for an hour, and then only the Ba cells were inoculated ---> the mice died
5. When Hi/pVir was first heat-killed before being mixed with live Ba, the mixed cells were incubated for an hour, and then only the Ba cells were inoculated → the mice lived
a) Which was the method of DNA transfer: transformation, transduction, or conjugation? Explain your answer, including discussion of which species was the recipient and donor.