Fire is not alive because it is does not have cells. All known living things have cells
Also, fire does not follow the levels of organization found in living things i.e. cell, tissue, organ, organ system. It can create more of itself, but it does not reproduce through a means of cellular division. Both sexual and asexual reproduction involve cellular division, which fire lacks.
It uses oxygen from the air, but it technically does not "respire" because it lacks cells, and therefore cannot perform cellular respiration, a process that all known living things take part in.
It does not have homeostasis, the process through which organisms maintain a stable, constant internal environment. It does not possess instinct. For example, if fire had instinct, it would be aware that water is bad for it, and would try to avoid water, thus if you threw water at a fire, the fire would make an attempt to avoid it.
if we were to discover something that was somehow alive without having cells, DNA, etc, we would have to rethink how we define life. Since there are no energy organisms, at least any that are known off, something that lacks mass can't be alive, although as I just mentioned, if we were to discover an "energy organism" then
Actually, the OP answered the question himself. It lacks cells and DNA, both of which are the building blocks of life.
Also, I think the OP is confusing consciousness with intelligence. If consciousness is defined as being aware of surroundings and reacting to them, yes an amoeba does have consciousness. But the way the OP describes consciousness makes it sound more like a description of intelligence.