The Ship of Theseus question is certainly relevant to a discussion of identity changing over time (our body's cells are constantly turning over), but I think it

The Ship of Theseus question is certainly relevant to a discussion of identity changing over time (our body's cells are constantly turning over), but I think it's completely unrelated to a discussion of the line between my gut bacteria and me. Though to answer your question, "I" am an emergent phenomenon resulting from the interactions of the atoms in my body. "I" am just a wave passing through the universe, with my body as the medium of transmission. Similarly, "wind" is merely a description of what the air is doing where you are. As the wind blows, the specific air molecules you're observing as "the wind" are completely different from moment to moment, but a breeze persisting through an afternoon is all perceived as being the same wind.