Bees and Microorganisms

I have a question related to treatment free beekeeping and Dr. Elaine's SFW work.

I've listened to podcasts from Dr. Leo, and others who practice treatment free beekeeping. I've heard Dr. Leo talk about catching feral swarms because they have the genetics to resists pest and diseases. How much is this related to their genetics, and how much could be attributed to beneficial microorganism?

If microorganisms play a significant role in fighting pests/disease, is there a possibility to 'inoculate' hives the same way SFW inoculates plants and soil with beneficial microorganisms?

Side note: I'm about to return to the US and start a year sabbatical. I'll be in South Louisiana, and I want to learn as much as I can about treatment free beekeeping. Anybody in the area need a hand, I'll work for knowledge!