1- it contains sulfur when bacteria found sulfur in the media then it produces H2S (hydrogen sulfate). It causes the blackening of the media which acts as an indicator that bacteria can produce H2S.
2- Indol is the second characteristic. If bacteria is indol positive than it changes color from yellow to pink when the reagent is added.
3- Motility: if bacteria are motile than it's motility is easily visible in the media.
When these viruses insert their genome into the host cell, they usually have a reverse transcriptase enzyme that converts the RNA to DNA before it is integrated into the host genome. This is before the host cell machinery is hijacked to replicate the viruses components.
