Why is it necessarily an all or nothing question? Can't we simply say we concern ourselves more with complex organisms than less complex? That reveals the emptiness of this question of where you put the dividing line.

I don't needlessly kill bacteria, only when they threaten someone I love more than them do I kill them.

So yes there is a hierarchy, but they are on the list of things that are alive.

And if I first found bacteria in Mars, I would probably dedicate my life to preserving them depending on how abundant they are.

Morality is importantly a question for the individual. The question is, what do you weep for, not what do we weep for. If you're taking moral cues from others, you're not doing morality, just groupthink.