On: Gut microbe linked to depression in large health study

[ninesnines]

Hi!

Thanks a ton - super curious research. What determines if individuals get Morganella and Kiebdiella bacteria? Is it genetic or can it be impacted by the food we eat?

What is the mechanism of how these bacterias interact with the brain through the enteric system?

Thank you!

[wdwvt1 → ninesnines]

Fascinating question - also not totally known.

We know that microbes colonize the gut in a somewhat predictable way as a function of age. As a newborn your gut is largely dominated by Bifidobacteria, and this slowly transitions to a more complex community over the next several years of life. Events like early childhood antibiotics, malnutrition, other disease, etc. can alter this trajectory. Interestingly this kind of ecological succession seems to be driven by an interplay of both immune maturation (as your immune system matures it starts being more selective about who it tries to let in) and by chemical processes. The gut becomes more anaerobic as the number of bacteria increase (and transition away from the Bifido dominated state) and that has a strong selective effect on the microbes that will grow well.

For specific commensal bacteria we know some of the mechanisms of colonization - there are particular genetic programs that bacteria turn on when they sense they are in the gut to enhance their ability to be retained and not washed out. These programs include physical attachment, motility, and chemical signalling to try to dampen the local immune response.

Pathogens are extremely good at getting in to the gut despite our best attempts at keeping them out. Salmonella typhimurium is notoriously adept at colonizing the host - the infectious dose you need is maybe 10 microbes taken orally in a susceptible host (compare that to 10 billion microbes/capsule in a probiotic).

For these specific bugs I don't know that much. I am excited to read more.