Recently there has been increasing interest and research into symbiotic bacteria present in humans and human gut. I'm aware of two new discoveries:

I've also heard that mothers pass a lot of beneficial bacteria to children during childbirth to jump start intestinal flora. Apparently this happens as the baby travels through the birth canal.

This makes me ask - do adult humans share/ pass along symbiotic or beneficial bacteria or other micro organisms?

I'm aware of viruses and diseases that can be passed via blood or be transmitted sexually, but does anything beneficial get transmitted this way?

  • $\begingroup$ It comes down to a question of whether or not they are able to colonize the surfaces, skin, lungs, gut epithelium, not if they are exchanged. A large majority of gut microbiota are anaerobes and their ability to be passed in any medium other than direct contact with feces (how baby's born vaginally get their sampling of most of the maternal gut microbiome) is limited. $\endgroup$ – AMR Oct 30 '15 at 22:10
  • $\begingroup$ Also as an adult your own microbiome is part of your innate immune defenses and they keep out other organisms by taking up space on the exposed surfaces of the body. Pathogens have an advantage over commensals as they have virulence factors to let them gain the upper hand. $\endgroup$ – AMR Oct 30 '15 at 22:10
  1. Nonpathological bacteria Staphylococcus epidermidis on the human skin are part of normal bacterial flora that help to protect against pathogenic bacteria, such as Staphylococcus aureus. You can get "infected" by Staphylococcus epidermidis the same way as by other skin bacteria and you get a potential benefit from them. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2807625/

  2. You can get beneficial effects from pathological bacteria passed from someone, if you you develop antibodies to them, so you can become more or less resistant to them. For example, if you are from US or Europe and travel to South Asia, you at high risk to get food poisoning from either bacteria or viruses, bot local people are at much lower risk, because they have "shared" microbes one from another.

  3. You can get beneficial effects from probiotic supplements (live nonpathological bacteria), which prevent overgrowth of pathological bacteria in your large intestine. The bacteria in probiotics are similar than those in the human gut.

  • $\begingroup$ You forgot to add the most important bacteria when the baby passes through the birth canal. $\endgroup$ – Muze the good Troll. Apr 27 '19 at 0:20
  • $\begingroup$ @Muze, the question is strictly about adults. $\endgroup$ – Jan Apr 29 '19 at 7:26

Every human has it owns unique bacterial biome, and they acquire it the day they are born. Another interesting thing is that the bacteria that each individual acquires gets much of it from there family/parents. An analogy would be portions of bacterial biomes are passed down from generation to generation although each person does generally acquire a unique set of bacteria.

Bacteria is passed throughout the population all the time generally though you only hear about the negative transfers i.e pathogens. It is hard to track what gets transferred though as most bacteria is not culturable.

The Human Biome Project has been uncovering the variety of bacterial biomes among the human population in different demographics, etc. You would probably have a fun time looking through there and uncovering some cool information.

Here's the link: The Human Biome Project


Most exchanges, aside from neo-natal transfer, are fecal-oral. Some exchanges are pneumonic, but the study of those has been limited to pathogens. I am not aware of any studies of direct epithelial contact.

In humans, the preponderance of exchanges happen early in life (neo-natal). The current school of thought is that the microbiome is established by passing through the birth canal and through breast feeding. Only Archae and bacteria have been studied up to this point, and the study of the constellation of viruses is currently being proposed.


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