The Sexome: Your Intimate Microbiome Has a Fingerprint

Your body is home to trillions of microorganisms. They live on your skin, in your gut, and in your most intimate places — forming complex, dynamic ecosystems that are as unique to you as your fingerprint.

Current research out of Australia is revealing something remarkable about the microbial communities that inhabit our genitals: they are transferable, traceable, and deeply interconnected with the people we are intimate with. Scientists have given this phenomenon a name — the sexome.

What Is the Sexome?

The sexome refers to the unique collection of microorganisms — bacteria, in particular — that reside on and within an individual's genitals, and which are exchanged during sexual contact.

In 2025, forensic scientists at Murdoch University in Western Australia published a landmark study in the peer-reviewed journal iScience, providing the first robust scientific evidence that heterosexual couples exchange genital bacteria during intercourse  and that these microbial signatures are detectable, partner-specific, and forensically meaningful.

The research team collected and genetically sequenced baseline genital microbiome samples from 12 monogamous heterosexual couples. Participants abstained from intercourse for a period of between two and fourteen days, after which the couples had intercourse and a second round of samples was collected. Using long-read genetic sequencing technology (precise enough to distinguish individual bacterial sub-species) the researchers compared the before and after profiles.

What they found was unambiguous: both partners carried detectable bacterial DNA from the other after a single sexual encounter. Female microbial signatures were found on male genitals. Male signatures were found in the vaginal environment. The transfer was bidirectional, partner-specific, and consistent across participants.

A New Forensic Tool — Especially When Conventional Evidence Fails

The implications extend well beyond intimate health. The study was designed with forensic science in mind — specifically, to address one of the most persistent limitations in sexual assault investigations.

Standard forensic rape kits rely on detecting semen. In cases where a perpetrator uses a condom or does not ejaculate, this evidence is simply absent, leaving investigators without biological proof of contact.

The sexome offers a potential solution.

Three of the couples in the Murdoch study used condoms during intercourse — and microbial transfer was still detected. Notably, when a condom was used, the majority of transfer occurred from the female to the male — a finding with significant implications for testing perpetrators post-assault.

"This shows promise for a means of testing a perpetrator post-assault and means there may be microbial markers that detect sexual contact even when a condom was used."

— Ruby Dixon, Forensic Scientist, Murdoch University

"In forensic science, we work on the concept that all contact leaves a trace behind. With fingerprints, that's obviously the residues from our skin, and in the case of the sexome, we're using the healthy bacterial communities living on, and within, our bodies as a means of detecting that transfer."

— Brendan Chapman, Forensic Scientist, Murdoch University

Researchers also found that microbial traces persisted for some time after intercourse — suggesting forensic detection may remain possible beyond the typical window in which sperm can be identified. Circumcision status and pubic hair were found to have no significant effect on the degree of bacterial exchange. Menstruation, however, altered the vaginal sexome — an important variable for forensic timelines.

The Land and Sea of the Genital Microbiome

What makes the sexome particularly traceable is the fundamental difference between vaginal and penile microbial environments.

The vaginal microbiome is low-diversity by design — dominated by Lactobacillus species that maintain an acidic pH below 4.5 through lactic acid production. This acidity is protective, directly inhibiting a range of pathogens. In the vaginal ecosystem, diversity is a warning sign, not a strength.

The penile microbiome, by contrast, is naturally more diverse — populated by Corynebacterium, Streptococcus, Prevotella, Anaerococcus, and other organisms that are rarely found in a healthy vaginal environment.

"The great benefit we have with the penile and vaginal microbiomes is that because of the vast difference in the two environments, we observe very different bacteria types on each. It's a bit like comparing land and sea animals — there are some that exclusively live in one or the other location and would die if removed, but also some that happily move between and persist."

— Brendan Chapman, Murdoch University

It is precisely this difference that makes microbial transfer detectable — and potentially forensically useful.

What the Sexome Means for Intimate Health

Beyond forensic science, the sexome research affirms something that intimate health advocates — including those of us at Nunie — have long understood: sexual encounters are microbial events, and the health of both partners' microbiomes matters.

We have known for some time that the penile microbiome can directly influence vaginal microbiome balance. Research has previously shown that men whose genital microbiomes harbour high levels of BV-associated anaerobes — organisms like Prevotella, Peptoniphilus, and Finegoldia — are significantly more likely to have female partners with bacterial vaginosis (BV). The sexome study adds a finer resolution to this picture: the transfer is specific, bidirectional, and occurs with every encounter.

This has several practical implications for intimate wellbeing:

• Recurrent BV may have a partner-source component. If your partner's penile microbiome harbours BV-associated organisms, re-exposure during unprotected sex may be contributing to recurrence — even after successful treatment.
• Condoms reduce but do not eliminate microbial exchange. They remain the most effective barrier, but the sexome data confirms they are not a complete microbial seal.
• Intimate microbiome care is a shared responsibility. Supporting a balanced, low-anaerobe genital microbiome is not just beneficial for the individual — it is a contribution to a partner's health ecosystem.
• Your sexual history has a microbial record. Over time, long-term partners may experience some degree of sexome homogenisation — a gradual convergence of their microbial communities through sustained exchange.

The Science Is Still Emerging — But the Principle Is Clear

The sexome as a field is in its early stages. The Murdoch University study is an important proof-of-concept, but it involved a small, monogamous, heterosexual cohort. Larger studies across diverse relationship structures, sexual practices, and anatomical contexts will be needed before the sexome can be applied as a reliable forensic tool.

What the research does confirm, however, is a principle that underpins everything we do at Nunie: every intimate encounter is a biological exchange. The microorganisms living in and on our bodies do not observe the same boundaries we do. They move, transfer, persist — and shape each other's ecosystems.

Understanding this is not cause for anxiety. It is an invitation to approach intimate health with the same intentionality we bring to every other aspect of our wellbeing.

A Note From Nunie

We have always believed that intimate health is shared health. The sexome research reinforces why we formulate our products for all bodies — not just the vaginal environment — and why we think of Bedroom Butter as a product that supports the entire intimate ecosystem, not just one partner.

Plant actives that calm inflammation, reduce anaerobic bacterial burden, and support mucosal barrier integrity are not just personally beneficial. In the context of the sexome, they are a contribution to the shared microbial space you and your partner(s) inhabit together.

Healing and pleasure. Science and nature. At the same time, in the same sacred space.

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