It is a bit more complex than that. You probably would want to look at particular genes, rather than populations of bacteria. As with horizontal gene transfer

It is a bit more complex than that. You probably would want to look at particular genes, rather than populations of bacteria. As with horizontal gene transfer microbes readily exchange genetic material under environmental pressure. And as I understand, there isn't much research on that - "a genetic document is rather mute" - https://www.nature.com/articles/s41599-019-0251-8 https://www.nature.com/articles/s41599-019-0251-8