I don’t think I’m my cells or the bacteria living in my gut. Well, that’s not entirely true, I clearly perceive the cells in my hand and the bacteria in my gut as part of myself in some way but not the same way as other things.
Maybe this question is helpful: What do I care about? Clearly not my cells or microorganisms. I would be more than happy to dispose of my hip joint and replace it with titanium should that ever be necessary. I essentially think the same about every other part of my body.
I also don’t care about my DNA at all. If you cloned me after my death I wouldn’t suddenly spring to life, I wouldn’t be reborn as a baby, my clone would be a different person.
What do I care about, then? That, which says this sentence in my brain right now as I type it, whatever it is. It’s probably rooted in structures in my brain somewhere. Which doesn’t mean that I care about the cells in my brain, not at all. If there is a way to preserve that structure and run it I would be just fine. That’s what I care about.
That, to me, is the most important, probably the only really important part of me. The body matters but only in the sense of being a sort of tool.