Next the researchers repeated the experiment in part c but instead of mixing the ax and ay strains, they put one strain on each
side of a glass u-tube. the u-tube contains a glass filter between the two strains of bacteria that prevents the cells from interacting directly. on which type(s) of media would you expect cells from the ay side of the u-tube to grow?
Bacterial cells can transfer genetic material through a process called bacterial conjugation. This process involves the direct physical contact of the bacterial cells and a horizontal gene transfer. The genes which are transferred are most of the times beneficial for the recipient, such as genes for antibiotic resistance.
In this example, bacterial cells cannot have physical contact, since they are separated by a glass filter. Therefore, the bacterial conjugation cannot happen. Given that no gene transfer can be achieved, the AY strain remains bio- trp- and is unable to grow on any medium that lacks bio or/and trp.
This process would be the one truly responsible for the "evolution" of mitochondria and chloroplasts as we know them from their prokaryotic ancestors. The cell process that would have initiated endosymbiosis is endocytosis; the process of taking things inside the cell
