Just because you don't know they are there doesn't mean they aren't there!

It's like you've never heard that what you don't know can't hurt you.

Or help you. (e.g. play some important role in the wider ecosystem)

There are millions on the lower bound of bacteria species we havn't identified, trillions on the upper bound. Unknown bacteria are literally everywhere, but the simple act of finding and sequencing them is nothing to be afraid of.

Also known as biological dark matter: https://en.m.wikipedia.org/wiki/Biological_dark_matter

Sounds normal, most bacteria can’t be cultured. Only about 50% of the ones in your mouth can be

Meh, they came from the soil. It's always been here, just never seen by human eyes. That's true of lots and lots of bacteria though - we find new species pretty much every single time we take a stomach sample from someone, let alone random forest soil.

Many bacteria have commensal lifestyles —- scientists don’t feel in control if they can’t culture bacteria in isolation but in nature many bacteria aren’t metabolically complete and son’s live in isolation.