Our Closest Frenemies: Secrets of our Genital and Bellybutton Biomes
Most bacteria are, as people, “either good or simply present.” — The Belly Button Diversity Project
The Human Microbiome Project
identified many of the microorganisms found in the human body, revealing that, because we each have unique experiences in varied environments, we each have a unique microbiomic fingerprint. It is constantly changing its composition to maintain the balance that allows us to survive and thrive together.
The number and variety of microorganisms living on and within us are hard to grasp:
· Our body consists of 10% human cells and 90% microbial cells
· Altogether, they account for about 3% of our body weight, about 2 to 5 pounds
· Of all the genes contained in the cells of our bodies, 99% are from our microbes; only 1% are human!
The Belly Button Microbiome
We’re going to work our way down to the genitals from the belly button — it’s just too interesting to skip. In 2011, a group of undergrads from North Carolina State University had the genius idea of enticing public interest in science by swabbing belly buttons for bacteria. They had no difficulty finding 60 volunteers among visitors attending a North Carolina Museum of Natural Science conference. The results astounded them.
The officially named ‘Belly Button Diversity Project’ found that most belly buttons harbored about 67 species of bacteria, ranging from 29 to 107. Overall, they identified over 2300 different species, of which over 1400 may be new to science. One navel housed a microbe that had previously only been found in the soil in Japan. He had never been to Japan. Another navel gave up two bacteria usually found in extreme locations: ice caps near the poles and thermal vents in the deep ocean. (These were found in a volunteer who volunteered that he had not bathed in several years.) While the majority of species identified were common skin microbes, none of the microbes were found in all of the navels, and 30% of the navels did not contain the most common microbes. The chief researcher likened the belly button microbiome to a diverse, beautiful rainforest containing secrets yet to be discovered.
The Human Microbiome
The human microbiome is a characteristic (unique to you) community of microbes interacting with each other and its host (you) in a dynamic interplay necessary for the functioning and health of the community and the host. More than ten thousand different microorganisms colonize our bodies — bacteria, fungi, viruses, and protozoa.
We have microbial ecosystems everywhere — in our gut, nose, mouth, throat, ear, urethra, penis, vagina, on our skin, in our breastmilk, everywhere. Some spots are more profusely jungled than others. Since microbes prefer dark and moist to clean and dry, the gatherings are sparser on the shoulder than they are in the armpit, for example.
The great majority of these microbial creatures are friendly, living right along with us, even streamlining necessary body functions that we’d rather not think about. Food digestion and fecal formation come to mind. There are the few miscreants (the pathogens) that give the rest a bad reputation. But pathogenic organisms make up only a tiny fraction of our microbiome, and these are normally held in balance by the other microbes. Illness may arise from ‘dysbiosis’ — a change from our usual biome diversity and composition that can impact our immune system and permit internal or external pathogens to prevail.
The Penile Microbiome
Yes, the penis has a biome, just like every other part of our bodies, including the lungs, the placenta, and the urethra — all of which, at one time, was thought to be sterile. Each biological man has their own unique mix of bacteria inhabiting their genitals.
The normal microbiota of the biologically male genitals is found primarily within the distal urethra and on the skin. There are many fewer microbes on the penis than in the mouth or the vagina because most penile skin is external. The mouth and vagina are dark and moist environments covered in delicate skin (mucous membrane) — much more appealing to microbes.
The uncircumcised penis has more of these characteristics and therefore harbors more anaerobic bacteria than a circumcised penis. Anaerobic bacteria, the kind that can cause the most difficult problems like pelvic inflammatory disease (PID), bacterial vaginosis (BV), and septic abortion, don’t like sunlight and oxygen. Removing the foreskin exposes more penile skin to the air forcing the anaerobic bacteria to find someplace else to live. Overall, the lower bacterial load and fewer “bad” pathogens can result in a decreased risk of contracting HIV (human immunodeficiency virus), HPV (human papilloma virus), and HSV (herpes simplex virus), among other sexually transmitted infections (STIs).
In areas where the risk of acquiring HIV is high, some biological men are choosing to be circumcised. However, circumcision is a highly culturized tradition — globally, about 30 to 40 percent of men are circumcised — so the decision is highly personal and is only one of many effective methods of STI prevention.
Besides what resides on the penis, microbes can also inhabit the biological male ureter, bladder, prostate, and ejaculate. According to Larry Forney from the University of Idaho, about 10 million bacteria in one milliliter (about 15 drops) of ejaculate. That’s compared to 100 million bacteria per milliliter of vaginal secretions. Vaginas make better petri dishes.
Studies of the bacteria in semen identified three main varieties — one dominated by Prevotella (sounds like an Italian cheese), one dominated by Lactobacillus, which is also the predominant bacteria in the vagina with no dominant bacteria (polymicrobial). Effects of the differing biotas on the strength, motility, and a number of sperm is under study — any one type is not yet known to be more correlated with male infertility than any other type. These dominant varieties seem to exist regardless of race or geographic location; however, they may be influenced by age and hygiene.
The Vaginal Microbiome
The vagina presents an opportunity to understand the collaboration of individual members of the microbiome with the host to maintain the health of both. The predominant species of bacteria in most vaginas is Lactobacillus. It’s the same bacteria that turn milk into yogurt and sourdough starter into bread. Yum! Estrogens produced by the hormones in the body are the source of the sugars that the Lactobacilli ferment to produce lactic acid. Hormonal birth control methods contribute to estrogens too.
In the vagina, the lactic acid lowers the pH of the vagina to about 4 to 4.5, lower than the neutral 7 found in most of the rest of the body. This acidic environment is inhospitable to many pathogens and fungi, thereby preventing infections. When the numbers of Lactobacilli are low like after taking antibiotics, an overgrowth of opportunistic bacteria can occur. For example, Candida, normally held in check by the low pH, can now overgrow into a full-blown yeast infection.
More than 50 microbial species have been found in the vaginal. The key is keeping them all in a healthy balance. Medications, douching, low estrogen levels, and the introduction of external pathogens can mess up the delicate balance. An unbalanced microbiome, called vaginal dysbiosis, increases one’s risk for acquiring HIV and other STIs, pelvic inflammatory disease (PID), and adverse pregnancy outcomes such as preterm birth and maternal and neonatal infections. We need to take good care of our microbiomes.
Our Microbiomes Together
Penises and vaginas have individual microbial characteristics — what happens when they interact? Mouths, penises, vaginas, and anuses get together and share their microbiomes. They adapt to each other, each contributing bacteria to the other. Aww, sweet! Like moving in together and mixing the silverware.
But vagina owners beware, says Dr. Janneke van de Wijert at the University of Liverpool, UK. Having a new sex partner “is a microbial assault on the vagina,” she says. “The vagina will mount an immune response against the bacteria, causing inflammation” — and that raises the risk of getting an STI.
During heterosexual intercourse, even though biological women have more microbes in their vaginal secretions, they are more vulnerable to acquiring STIs than biological men. The vaginal skin is fragile, and the volume of semen left in the vagina exceeds the volume of vaginal secretions that are left on the tougher skin of the penis. More vaginas get STIs from infected penises than penises get STIs from infected vaginas. Dr. Hunter Handsfield at the University of Washington Center for AIDS and STDs calls this “biological sexism.”
During anal sex, both women and men who have receptive anal intercourse are at higher risk of acquiring STIs. The lining of the rectum is composed of the more porous and fragile mucous membrane too. Plus, the rectum is home to microbes from the gastrointestinal (GI) tract that wasn’t really meant for the genitals.
The Care and Feeding of our Microbiomes
The exciting news is that the human microbiome is emerging as a potential target for personalized medicine. Treatments for diseases based on individual microbial signatures are being explored. These may include dietary adjustments, probiotics, synbiotics (synthetic microorganisms), and microbiome transfers (think fecal transplants).
To avoid infections that may need these new therapies, here are some recommendations on how to keep your microbiome healthy:
· Use condoms — for vaginal and anal sex, especially if you are not in a long-term monogamous relationship.
· Biological women: Don’t douche! It messes with the balance of your organisms.
· Don’t use chemicals, perfumes, or other products on your genitals.
· If you have abnormal secretions, smells, pain with or without sexual activity — get STI tested as soon as possible.
· If you have a new sex partner, both of you get tested. Repeat in 3 months if either of you had other recent partners.
· Eat right. Don’t feed the yeast with sugar.
· Cotton underwear during the day, no underwear at night. Give your genitals some air!
· Practice good hygiene, so you don’t come home with a microbe from Japan or from deep in the sea!
Watch for news on the human microbiome. We still have much to discover. I think we’ll have some important breakthroughs in the near future.
Kristine Shields is a doctor of public health and a former women’s health nurse practitioner. Find more of her obsession with sexual health and her Paddendum newsletter at kristineshieldsauthor.com.
