Thanks for commenting! :)
I must say that in our own garden we don't use any chemicals (neither artificial fertilizers nor any pesticides). My personal believe is that they impair the quality of the soil (and can also harm useful insects) in the long run. Some articles are supporting my point of view. For example here you can read "Synthetic fertilizers kill a large percentage of a soil's naturally-occurring microorganisms."
On the other side there are of course different opinions as well and the matter is rather complex. That means it is not so easy to make a simple conclusion like "All chemicals are always bad." Of course it also depends on what exactly you use and how much ...
Concerning M. vaccae I don't know if it is more, less or equally affected than/as other soil bacteria.
RE: Does inhaling bacteria increase intelligence?