Dave, I'm a scifi buff and when I hear the phrase, 'We are not alone' to talk about aliens and fears about being conquered, I can't help but think we're already there. Except I'm talking about 'intra-terrestrials'.

Right, true! You're talking about our microbiome, the microbes which are mostly fungi and bacteria that outnumber our own cells by more than one hundred times. Exactly, you could argue that these microbes already exert huge influences on us.

Changing their makeup can cause obesity, irritable bowel syndrome, skin diseases and even affect our moods and behavior. That's why one area of biomedical research now explores connections between the microbiome in our gut and the health of our brain, the so-called gut microbiota ' brain axis!

They've already discovered that communication between the microbes and the brain is bidirectional. The nerve structure in the intestinal track is an important source of this communication. That makes sense since the intestinal track has the highest concentration of neurons outside the brain. Plus, our immune systems send molecules called cytokines and chemokines between the brain and gut as messengers. Neuropeptides and microbial products also transmit messaging.

Disrupting all this communication may lead to ADHD, depression, anxiety, and autism spectrum disorder. There is accumulating evidence that a subclass of probiotics called psychobiotics can affect cognitive function. Certain bacteria may lower anti-inflammatory effects in the brain to make it more resistant to stress.

We're only beginning to understand this complex relationship and I say, more power to intraterrestrials.