I wasn't sure. At first I would have assumed there to be a small but significant difference. The difference in hormones should create distinct environments so a

I wasn't sure. At first I would have assumed there to be a small but significant difference. The difference in hormones should create distinct environments so a bacterium that can take advantage of that difference would be more likely to occur in one sex than the other. Probably the male as female is the default sex. (Is there any species that starts as male?) What this tells me is that animals are conservative with their hormones. Allowing arbitrary proteins to seep into our gut would be wasteful. There's also that if we allowed bacteria to be affected by our sex hormones, that would also make our reproduction susceptible to alteration by those bacteria. Natural selection cuts the finest when it comes to the genes involved in procreation. So it should be rare to find a symbiotic organism with a sex organ. Viral organisms of course don't care if the host dies, or can't have babies.