All cells (bacteria, as well as body cells) function from instructions from their DNA. The (master copy of) DNA gets copied to (working copies of) RNA (single strands of instructions) and then the cell's proteins execute the instructions.

Viruses are NOT alive because they do not have all of the internal processes and organelles that cells have. They just have RNA protected by a sheath. If a cell takes in a virus, the cell's instructions will get corrupted.