The Ecology of Humans (2-2) Microbiome continued 1


The personalized microbiome affects every facet of life, including psychology. Not only does the herpes virus help keep the engine running clean, it motivates sexual intercourse, based upon environmental cues it receives that the possibility of sex exists, such as increased oxytocin levels.

Eating the bacteria Lactobacillus rhamnosus, found in certain yogurts, cheeses, and breads, has a calming effect. Gut bacteria influence mood via the vagus nerve, which connects the digestive organs to the brain.

Scientists have only begun to explore human-microbial codependence and interrelationship. The most rudimentary knowledge of human-microbe interdependence was just discovered at the turn of the millennium. Researchers have yet to discover the energetic interactivity that most essentially characterizes the ongoing dialogue between microbiome and host. Yet the microbiome was known by the mid-1600s, when Dutch lens-grinder Antonie van Leeuwenhoek scraped some scum off his teeth, put it under a microscope, and discovered a swarm of little swimmers. Each tooth, even each side of each tooth, has various combinations of different bacteria.

The skin is the physical ecological interface between a body and its environment. Microbes there play an essential protective role. They also define your presence. The microbiome can smooth your skin and make your hair shiny. They can collectively put a spring your step.

Everyone has their own biogeographical colonies of microbes. The hair, the forehead, the ear, around the eyes and the nose all have different bacterial colonies; as do the elbow and the forearm, and each finger. Bacteria from a person’s tongue can make a decent living on a dry forearm, but the oily forehead is tough going.

Human skin is a smorgasbord of microbial ecosystems: home to roughly 1,000 bacteria species, almost as many as working the intestinal tract. Colonies vary by individual and by health.

The skin needs microbial signals for proper immune cell function. ~ Indian immunologist Shruti Naik

Each type of microbe on the skin triggers a specific immune response. Microbial skin commensals and the host immune system form an effective team to protect the home turf.

The most bacterially diverse region of the skin is on the forearm: home to nearly 4 dozen species on average, double the number found in the most barren patch, behind the ears.

While many skin bacteria pose a potential infection risk if able to penetrate the skin’s multiple defenses, Staphylococcus epidermidis helps tune the immune system. S. epidermidis blocks aggressive inflammatory agents with a molecular signal. Unchecked, the agents would be hyperactive, igniting a rash reaction around even a slight scrape.

Belly-button bacteria are a stable group, lasting months with little change. There are other quiet portions of the body, while other parts, such as the mouth and skin, are transit centers and quite active microbiotically.

Commensal vaginal bacteria secrete compounds that keep pathogens in check, rendering the environment slightly acidic, which most microbes find unappealing.

Indigenous microbes in the mouth and lungs not only adhere to local cells, they comingle with them as well. Conditions are much different there than on the skin. The purpose and effects are not understood. It may well be an intimate form of communication and sharing.

Whereas the lower respiratory tract lacks a microbial community, the upper respiratory tract is densely populated with microbes, with a high species diversity for healthy humans which varies from site to site.

We are colonized by microbes every day of life: from surfaces touched, food consumed, and air breathed. Some microbes mitigate invasion. Bacteria in our nose manufacture antibiotics to kill dangerous pathogens that are sniffed.