Scientists divide bacteria into so-called "gram positive" varieties like Strep, which lack rigid cell walls and can be stained with dye, and "gram negative" ones that have cell walls and aren't dyeable.
The system the researchers tested used a type of solar cell known as dye-sensitized solar cells, a lightweight and inexpensive type where the active layer is composed of titanium dioxide, rather than the silicon used in conventional solar cells.
By changing the composition of the dye, G24's engineers ensure that the maximum sensitivity of the cell coincides with whatever frequency mix is appropriate for the artificial light concerned.