[wdwvt1]

Just wanted to add some color to this good comment.

In the human context we are much closer to being able to culture anything we want. I would estimate that we are at 75% coverage now -- pick a species detected genomically in the human gut (or skin/vagina/nose, etc.) and we are likely to be able to culture it or a type strain of its species 75% of the time. For a long time we overestimated human microbial diversity because of bad genomic methods and error rates with the early 454 and then Illumina sequencers. This error rate, coupled with the fact that we can't easily replicate culture conditions for the vast majority of earth's bacterial biomass (i.e. the deep lithosphere or the oceans) led to this persistent if somewhat untrue description of the unculturability of human microbes.

[0] gives an estimate of 35-65% of human/mouse gut microbes having a culturable representative. This paper is from 2017, and there have been a lot of advancements since then.

[1] is a good non-review paper where they got 73% of the genomically defined species via just a single cultivation medium

There are others, but I finished my PhD in culturomics-related stuff in 2021, and haven't kept up as much as I should. Everything the OP cited about lithospheric, deep ocean, etc. still applies as far as I know. Those environments are just very hard to recreate with their pressure, temperature, and nutrient requirements.

[0] https://doi.org/10.1038/s41564-023-01426-7 [1] https://www.nature.com/articles/nature17645

Edit: typos