And now the diversity of our gut bacteria seems to affect our hormones!

It is fascinating seeing the interaction between the microbiome (the bacterial population) of a large bowel and the function of other systems in the body (immune, endocrine) being explored and gradually better understood. See this recent article.

It is now clear that our traditional way of seeing ourselves us as living organisms that are 'apart' from bacteria, worms and viruses (the way that biology is taught, with the conventional view of the immune system as fighting 'foreign invaders') is completely wrong. 

The reality is that we exist in a much more fluid and shifting way with foreign organisms, some of whom help, some hinder, and some (appear to) do nothing.