Staphylococcus aureus lipid factors modulate melanoma cell clustering and invasion.

The microbiome can influence cancer development and progression. However, less is known about the role of the skin microbiota in melanoma. Here, we took advantage of a zebrafish melanoma model to probe the effects of Staphylococcus aureus on melanoma invasion. We found that S. aureus produces factors that enhance melanoma invasion and dissemination in zebrafish larvae. We used a published in vitro 3D cluster formation assay that correlates increased clustering with tumor invasion. S. aureus supernatant increased clustering of melanoma cells and was abrogated by a Rho-Kinase inhibitor, implicating a role for Rho-GTPases. The melanoma clustering response was specific to S. aureus but not to other staphylococcal species, including S. epidermidis. Our findings suggest that S. aureus promotes melanoma clustering and invasion via lipids generated by the lipase Sal2 (officially known as GehB). Taken together, these findings suggest that specific bacterial products mediate melanoma invasive migration in zebrafish.

Characteristics of Malassezia furfur at various pH and effects of Malassezia lipids on skin cells.

Malassezia species are commensal and opportunistic fungi found in human skin. All Malassezia species lack fatty acid synthesis genes and survive by utilizing several lipases to degrade and absorb fatty acids from external lipid sources, but little research has been done on their optimal active pH and temperature. Our skin protects itself from external stimuli and maintains homeostasis, involving bacteria and fungi such as Malassezia species that inhabit our skin. Hence, dysbiosis in the skin microbiome can lead to various skin diseases. The skin's pH is slightly acidic compared to neutral, and changes in pH can affect the metabolism of Malassezia species. We used keratinocyte cell lines to determine the effect of lipids bio-converted by Malassezia furfur, Malassezia japonica, and Malassezia yamatoensis under pH conditions similar to those of healthy skin. Lipids bio-converted from Malassezia species were associated with the regulation of transcripts related to inflammation, moisturizing, and promoting elasticity. Therefore, to determine the effect of pH on lipid metabolism in M. furfur, which is associated with seborrheic dermatitis, changes in biomass, lipid content, and fatty acid composition were determined. The results showed that pH 7 resulted in low growth and reduced lipid content, which had a negative impact on skin health. Given that bio-converted Malassezia-derived lipids show positive effects at the slightly acidic pH typical of healthy skin, it is important to study their effects on skin cells under various pH conditions. KEY POINTS: • pH 6, Malassezia spp. bio-converted lipid have a positive effect on skin cells • Malassezia spp. have different lipid, fatty acid, and growth depending on pH • Malassezia spp. can play a beneficial role by secreting lipids to the outside.

Skin microbiome and causal relationships in three dermatological diseases: Evidence from Mendelian randomization and Bayesian weighting.

BACKGROUND: Atopic dermatitis (AD), psoriasis (PSO), rosacea, and other related immune skin diseases are affected by multiple complex factors such as genetic and microbial components. This research investigates the causal relationships between specific skin microbiota and these diseases by using Mendelian randomization (MR), and Bayesian weighted Mendelian randomization (BWMR). METHODS: We utilized genome-wide association study (GWAS) data to analyze the associations between various skin bacteria and three dermatological diseases. Single nucleotide polymorphisms (SNPs) served as instrumental variables (IVs) in MR methods, including inverse variance weighted (IVW), and MR Egger. BWMR was employed to validate results and address pleiotropy. RESULTS: The IVW analysis identified significant associations between specific skin microbiota and dermatological diseases. ASV006_Dry, ASV076_Dry, and Haemophilus_Dry were significantly positively associated with AD, whereas Kocuria_Dry was negatively associated. In PSO, ASV005_Dry was negatively associated, whereas ASV004_Dry, Rothia_Dry, and Streptococcus_Moist showed positive associations. For rosacea, ASV023_Dry was significantly positively associated, while ASV016_Moist, Finegoldia_Dry, and Rhodobacteraceae_Moist were significantly negatively associated. These results were corroborated by BWMR analysis. CONCLUSION: Bacterial species such as Finegoldia, Rothia, and Streptococcus play crucial roles in the pathogenesis of AD, PSO, and rosacea. Understanding these microbial interactions can aid in developing targeted treatments and preventive strategies, enhancing patient outcomes and quality of life.

Patho-immunological mechanisms of atopic dermatitis: The role of the three major human microbiomes.

Atopic dermatitis (AD) is a genetically predisposed allergic inflammatory dermatosis with chronic, pruritic, and recurrent features. Patients with AD have dry and itchy skin, often accompanied by chronic eczematous lesions, allergic rhinitis, or asthma, which has a considerable impact on their daily lives. With advances in genome sequencing technology, it has been demonstrated that microorganisms are involved in this disease, and the microorganisms associated with AD are attracting considerable research attention. An increasing number of studies conducted in recent years have demonstrated that an imbalanced microbiome in AD patients has substantial impact on disease prognosis, and the causes are closely tied to various immune mechanisms. However, the involvement of microorganisms in the pathogenesis of AD remains poorly understood. In this paper, we review the advances in research on the immunological mechanisms of the skin microbiome, intestinal microbiome, and lung microbiome that are related to AD prognosis and immunotherapy protocols. It is hoped that this approach will lay the foundation for exploring the pathogenesis of and emerging treatments for AD.

Dermatological Health in the Light of Skin Microbiome Evolution.

BACKGROUND: The complex ecosystem of the skin microbiome is essential for skin health by acting as a primary defense against infections, regulating immune responses, and maintaining barrier integrity. This literature review aims to consolidate existing information on the skin microbiome, focusing on its composition, functionality, importance, and its impact on skin aging. METHODS: An exhaustive exploration of scholarly literature was performed utilizing electronic databases including PubMed, Google Scholar, and ResearchGate, focusing on studies published between 2011 and 2024. Keywords included "skin microbiome," "skin microbiota," and "aging skin." Studies involving human subjects that focused on the skin microbiome's relationship with skin health were included. Out of 100 initially identified studies, 70 met the inclusion criteria and were reviewed. RESULTS: Studies showed that aging is associated with a reduction in the variety of microorganisms of the skin microbiome, leading to an increased susceptibility to skin conditions. Consequently, this underlines the interest in bacteriotherapy, mainly topical probiotics, to reinforce the skin microbiome in older adults, suggesting improvements in skin health and a reduction in age-related skin conditions. Further exploration is needed into the microbiome's role in skin health and the development of innovative, microbe-based skincare products. Biotherapeutic approaches, including the use of phages, endolysins, probiotics, prebiotics, postbiotics, and microbiome transplantation, can restore balance and enhance skin health. This article also addresses regulatory standards in the EU and the USA that ensure the safety and effectiveness of microbial skincare products. CONCLUSION: This review underscores the need to advance research on the skin microbiome's role in cosmetic enhancements and tailored skincare solutions, highlighting a great interest in leveraging microbial communities for dermatological benefits.

Valorisation of tomato pomace in anti-pollution and microbiome-balance face cream.

Tomato pomace, the main by-product of tomato processing, is also an underestimated source of many active substances. This study aimed to determine the possibility of using oil obtained from tomato pomace in a face cream formulation. The bacterial community structure, face skin biophysical parameters and protection against air pollution were examined after daily application of the cosmetic by volunteers. In the tomato pomace oil, the profile of fatty acids was determined by GC‒MS, and the profile of volatile compounds was determined using the HS-SPME technique. The dominant bioactive component in the oil was linoleic acid (63.6%), and among the volatile compounds, it was carvotanacetone (25.8%). The application of the cream with tomato pomace oil resulted in an increase in the dominant genera Staphylococcus, Anaerococcus and Cutibacterium in the epibiome, particularly beneficial Staphylococcus epidermidis, while limiting the growth of the potentially opportunistic pathogens Kocuria spp., Micrococcus spp., Veillonella spp., and Rothia spp. This study showed the usefulness of tomato pomace oil as a natural ingredient in skin care cosmetics, reducing skin inflammation, sensitivity and melanin level, with potential protective effects against air pollution and microbiome-balance properties. Tomato pomace, which is commonly considered waste after tomato processing, can be used in the development of new cosmetics and may additionally contribute to reducing environmental nuisance.

Isolation, genomic analysis and functional characterization of Enterococcus rotai CMTB-CA6, a putative probiotic strain isolated from a medicinal plant Centella asiatica.

Probiotics and their derivatives offer significant health benefits by supporting digestive health, boosting the immune system, and regulating the microbiomes not only of the internal gastrointestinal track but also of the skin. To be effective, probiotics and their derivatives must exhibit robust antimicrobial activity, resilience to adverse conditions, and colonization capabilities in host tissues. As an alternative to animal-derived probiotics, plant-derived lactic acid bacteria (LAB) present promising advantages, including enhanced diversity and tolerance to challenging environments. Our study focuses on exploring the potential of plant-derived LAB, particularly from the medicinal plant Centella asiatica, in improving skin conditions. Through a bacterial isolation procedure from C. asiatica leaves, Enterococcus rotai CMTB-CA6 was identified via 16S rRNA sequencing, whole genome sequencing, and bioinformatic analyses. Based on genomic analysis, antimicrobial-resistance and virulence genes were not detected. Additionally, the potential functions of E. rotai CMTB-CA6 were characterized by its lysates' ability to regulate skin microbes, such as stimulating the growth of Staphylococcus epidermidis while inhibiting that of Cutibacterium acnes, to restore the viability of human dermal fibroblasts under inflammatory conditions, and to demonstrate effective antioxidant activities both in a cell-free system and in human dermal fibroblasts. Our investigation revealed the efficacy of E. rotai CMTB-CA6 lysates in improving skin conditions, suggesting its potential use as a probiotic-derived agent for skin care products. Considering the ecological relationship between plant-inhabited bacteria and their host plants, we suggest that the utilization of E. rotai CMTB-CA6 strain for fermenting its host plant, C. asiatica, could be a novel approach to efficiently enriching bioactive molecules for human health benefits.

Microbial Dysbiosis in the Skin Microbiome and Its Psychological Consequences.

The homeostasis of the skin microbiome can be disrupted by both extrinsic and intrinsic factors, leading to a state of dysbiosis. This imbalance has been observed at the onset of persistent skin diseases that are closely linked to mental health conditions like anxiety and depression. This narrative review explores recent findings on the relationship between the skin microbiome and the pathophysiology of specific skin disorders, including acne vulgaris, atopic dermatitis, psoriasis, and wound infections. Additionally, it examines the psychological impact of these skin disorders, emphasizing their effect on patients' quality of life and their association with significant psychological consequences, such as anxiety, depression, stress, and suicidal ideation in the most severe cases.

Polyphenol-Rich Cranberry Beverage Positively Affected Skin Health, Skin Lipids, Skin Microbiome, Inflammation, and Oxidative Stress in Women in a Randomized Controlled Trial.

This study aimed to determine whether a polyphenol-rich cranberry beverage affects skin properties, lipids, and the microbiome in women using a randomized, double-blinded, placebo-controlled, cross-over design. Twenty-two women with Fitzpatrick skin types 2-3 were randomized to drink a cranberry beverage or placebo for six weeks. After a 21-day washout, they consumed the opposite beverage for six weeks. Six weeks of cranberry beverage significantly reduced UVB-induced erythema, improved net elasticity on the face and forearm, smoothness on the face, and gross elasticity on the forearm compared to the placebo. When stratified by age, these effects of the cranberry beverage were primarily observed in women >40 years old. SOD activities were improved after six weeks of cranberry beverage consumption compared to the placebo, while glutathione peroxide and TNF-α were improved compared to baseline. These effects were found to differ by age group. Skin lipid composition was modulated by both the cranberry beverage and the placebo. Cranberry beverages did not change α- or ß-diversity but altered the abundance of several skin microbes at the species and strain level. Consumption of a cranberry beverage for six weeks improved specific skin properties and oxidative stress and modulated skin lipids and microbiome compared to placebo.

A Custom qPCR Assay to Simultaneously Quantify Human and Microbial DNA.

To date, studies on microbial forensics have focused mainly on sequence analysis and generally do not include information on the quantification of and comparison between the human and bacterial DNA present in forensic samples. Knowing the amount of each type of DNA can be important for determining when and how best to employ bacterial DNA analysis, especially when there is insufficient human DNA for successful short tandem repeat (STR) typing. The goal of this work was to develop a quantitative PCR (qPCR) assay that simultaneously quantifies human and bacterial DNA that would be simple and cost-effective for laboratories to implement. Through a reproducibility study and several small-scale experiments, the reliability of a custom qPCR assay was established. A reproducibility study illustrated that the multiplex assay produced data comparable to that of previously established bacterial DNA and human DNA qPCR assays. The small-scale experiments showed that common surfaces such as keyboards (6.76 pg/µL), elevator buttons (11.9 pg/µL), cleaning supplies (7.17 pg/µL), and dispensers (16.4 pg/µL) failed to produce human DNA quantities sufficient for quality STR analysis (≥250 pg). However, all tested surfaces produced bacterial DNA quantities suitable for reaching 1 ng of amplified bacterial targets necessary for sequence analysis. In fact, bacterial DNA concentrations down to 10-8 ng/uL produce enough amplified product for sequencing. The newly developed qPCR multiplex tool will allow scientists to make better decisions regarding whether human or bacterial DNA analysis methods can be pursued during forensic or other investigations.

SkinCom, a synthetic skin microbial community, enables reproducible investigations of the human skin microbiome.

Existing models of the human skin have aided our understanding of skin health and disease. However, they currently lack a microbial component, despite microbes' demonstrated connections to various skin diseases. Here, we present a robust, standardized model of the skin microbial community (SkinCom) to support in vitro and in vivo investigations. Our methods lead to the formation of an accurate, reproducible, and diverse community of aerobic and anaerobic bacteria. Subsequent testing of SkinCom on the dorsal skin of mice allowed for DNA and RNA recovery from both the applied SkinCom and the dorsal skin, highlighting its practicality for in vivo studies and -omics analyses. Furthermore, 66% of the responses to common cosmetic chemicals in vitro were in agreement with a human trial. Therefore, SkinCom represents a valuable, standardized tool for investigating microbe-metabolite interactions and facilitates the experimental design of in vivo studies targeting host-microbe relationships.

A New Generation of Postbiotics for Skin and Scalp: In Situ Production of Lipid Metabolites by Malassezia.

Effects of pre- and probiotics on intestinal health are well researched and microbiome-targeting solutions are commercially available. Even though a trend to appreciate the presence of certain microbes on the skin is seeing an increase in momentum, our understanding is limited as to whether the utilization of skin-resident microbes for beneficial effects holds the same potential as the targeted manipulation of the gut microflora. Here, we present a selection of molecular mechanisms of cross-communication between human skin and the skin microbial community and the impact of these interactions on the host's cutaneous health with implications for the development of skin cosmetic and therapeutic solutions. Malassezia yeasts, as the main fungal representatives of the skin microfloral community, interact with the human host skin via lipid mediators, of which several are characterized by exhibiting potent anti-inflammatory activities. This review therefore puts a spotlight on Malassezia and provides a comprehensive overview of the current state of knowledge about these fungal-derived lipid mediators and their capability to reduce aesthetical and sensory burdens, such as redness and itching, commonly associated with inflammatory skin conditions. Finally, several examples of current skin microbiome-based interventions for cosmetic solutions are discussed, and models are presented for the use of skin-resident microbes as endogenous bio-manufacturing platforms for the in situ supplementation of the skin with beneficial metabolites.

COMPARATIVE WHOLE METAGENOME ANALYSIS IN LESIONAL AND NON-LESIONAL SCALP AREAS OF PSORIASIS CAPITIS PATIENTS AND HEALTHY INDIVIDUALS.

Psoriasis is an immune-mediated inflammatory disorder, where the majority of the patients suffer from psoriasis capitis or scalp psoriasis. Current therapeutics remain ineffective to treat scalp lesions. Here, we present a whole-metagenome characterisation of the scalp microbiome in psoriasis capitis. We investigated how changes in the homeostatic cutaneous microbiome correlate with the condition and identified metagenomic biomarkers (taxonomic, functional, virulence factors, antimicrobial resistance genes) that could partly explain its emergence. Within this study, 83 top and back scalp samples from healthy individuals and 64 lesional and non-lesional scalp samples from untreated psoriasis capitis subjects were analysed. Using qPCR targeting the 16S and 18S rRNA genes, we found a significant decrease in microbial load within scalp regions affected by psoriasis compared to their non-lesional counterparts. Metagenomic analysis revealed that psoriatic lesions displayed significant lower Cutibacterium species (incl. C. modestum, C. namnetense, C. granulosum, C. porci), along with an elevation in Staphylococcus aureus. A heightened relative presence of efflux pump protein-encoding genes was detected, suggesting potential antimicrobial resistance mechanisms. These mechanisms are known to specifically target human antimicrobial peptides (incl. cathelicidin LL-37) which are frequently encountered within psoriasis lesions. These shifts in microbial community dynamics may contribute to psoriasis disease pathogenesis.

The Human Skin Microbiome in Health: CME Part 1.

Human skin is home to a myriad of microorganisms, including bacteria, viruses, fungi, and mites, many of which are considered commensal microbes that aid in maintaining the overall homeostasis or steady-state condition of the skin and contribute to skin health. Our understanding of the complexities of the skin's interaction with its microorganisms is evolving. This knowledge is based primarily on in vitro and animal studies, and more work is needed to understand how this knowledge relates to humans. Here, we introduce the concept of the skin microbiome and discuss skin microbial ecology, some intrinsic factors with potential influence on the human skin microbiome, and possible microbiome-host interactions. The second article of this two-part CME series describes how microbiome alterations may be associated with skin disease, how medications can affect the microbiome, and what microbiome-based therapies are under investigation.

Social environment influences microbiota and potentially pathogenic bacterial communities on the skin of developing birds.

BACKGROUND: Animal bacterial symbionts are established early in life, either through vertical transmission and/or by horizontal transmission from both the physical and the social environment, such as direct contact with con- or heterospecifics. The social environment particularly can influence the acquisition of both mutualistic and pathogenic bacteria, with consequences for the stability of symbiotic communities. However, segregating the effects of the shared physical environment from those of the social interactions is challenging, limiting our current knowledge on the role of the social environment in structuring bacterial communities in wild animals. Here, we take advantage of the avian brood-parasite system of Eurasian magpies (Pica pica) and great spotted cuckoos (Clamator glandarius) to explore how the interspecific social environment (magpie nestlings developing with or without heterospecifics) affects bacterial communities on uropygial gland skin. RESULTS: We demonstrated interspecific differences in bacterial community compositions in members of the two species when growing up in monospecific nests. However, the bacterial community of magpies in heterospecific nests was richer, more diverse, and more similar to their cuckoo nest-mates than when growing up in monospecific nests. These patterns were alike for the subset of microbes that could be considered core, but when looking at the subset of potentially pathogenic bacterial genera, cuckoo presence reduced the relative abundance of potentially pathogenic bacterial genera on magpies. CONCLUSIONS: Our findings highlight the role of social interactions in shaping the assembly of the avian skin bacterial communities during the nestling period, as exemplified in a brood parasite-host system.

Effect of Topical Microencapsulated Benzoyl Peroxide on the Skin Microbiome in Rosacea: A Randomized, Double-Blind, Crossover, Vehicle-Controlled Clinical Trial.

Objective: We sought to evaluate changes in microbiome biodiversity and physical properties of the skin after eight weeks of once-daily topical microencapsulated benzoyl peroxide (E-BPO) compared to vehicle cream in participants with rosacea. Methods: This was a randomized, double-blind, crossover, single-center, vehicle-controlled evaluation of E-BPO on the skin microbiome in rosacea. Participants had facial rosacea with global severity of 3 or 4 on the Investigator Global Assessment (IGA) scale. In the Treatment 1-2 group, participants received E-BPO for eight weeks then switched to vehicle cream for four weeks. In the Treatment 2-1 group, participants received vehicle cream for eight weeks, then E-BPO for four weeks. Results: Thirty-one participants were enrolled and randomly assigned to either group. Demographic characteristics were comparable between the treatment groups. After eight weeks of E-BPO treatment, there was a marked reduction in the relative abundance of Staphylococcus accompanied by an increase in Cutibacterium. At the species level, there was an increase in the relative abundance of C. acnes and a decrease in abundance of S. epidermidis. No noticeable difference was detected at the genus or species level at Week 8 in the 2-1 group. Sebum level, IGA, lesion counts, facial erythema, and inflammatory scores were improved with E-BPO versus vehicle cream. Adverse events were mild or moderate in severity. Limitations: The study included a small number of subjects and only surface-swabs were used for microbiome sampling. Conclusion: E-BPO shifted the skin microbiome in rosacea and demonstrated improvements in clinical symptoms and skin physical properties and a well-tolerated safety profile. US National Library of Medicine; Trial ID: NCT05675501]; URL: clinicaltrials.gov.

Chronic Exposure to Petroleum-Derived Hydrocarbons Alters Human Skin Microbiome and Metabolome Profiles: A Pilot Study.

Petroleum-derived substances, like industrial oils and grease, are ubiquitous in our daily lives. Comprised of petroleum hydrocarbons (PH), these substances can come into contact with our skin, potentially causing molecular disruptions and contributing to the development of chronic disease. In this pilot study, we employed mass spectrometry-based untargeted metabolomics and 16S rRNA gene sequencing analyses to explore these effects. Superficial skin samples were collected from subjects with and without chronic dermal exposure to PH at two anatomical sites: the fingers (referred to as the hand) and arms (serving as an intersubject variability control). Exposed hands exhibited higher bacterial diversity (Shannon and Simpson indices) and an enrichment of oil-degrading bacteria (ODB), including Dietzia, Paracoccus, and Kocuria. Functional prediction suggested enriched pathways associated with PH degradation in exposed hands vs non-exposed hands, while no differences were observed when comparing the arms. Furthermore, carboxylic acids, glycerophospholipids, organooxygen compounds, phenol ethers, among others, were found to be more abundant in exposed hands. We observed positive correlations among multiple ODB and xenobiotics, suggesting a chemical remodeling of the skin favorable for ODB thriving. Overall, our study offers insights into the complex dysregulation of bacterial communities and the chemical milieu induced by chronic dermal exposure to PH.

Simple tape-stripping method for highly reliable and quantitative analysis of skin microbiome.

The composition of human skin microbiome profoundly impacts host skin health and disease. However, the relationship between skin homeostasis or the development of skin diseases and daily changes in skin microbial composition is poorly understood. Longitudinal samplings at more frequent intervals would address this issue, while conventional sampling methods have technical difficulties, leading to limitations in sampling opportunities. Here, we developed a simple and stable tape-stripping method regardless of the operator's skill. Our method enables skin microbial sampling within 30 seconds and taking multiple skin microbial samples from the same body site. The amount of microbial DNA among multiple sampling sites could be measured within 13.5%. The sequencing results of multiple sampling showed high consistency, Pearson's correlation coefficient between multiple samples of 0.98. Furthermore, these results were comparable to those collected by the conventional swabbing method. These results demonstrate that our tape-stripping method enables simple microbiome collection and highly reliable quantitative skin microbiome analysis. These features of our method would lead to a further understanding of skin disease development or diagnosis of skin conditions in clinical research by increasing the opportunities for microbial sampling.

Feasibility of engineered Bacillus subtilis for use as a microbiome-based topical drug delivery platform.

Non-adherence to medication is a major challenge in healthcare that results in worsened treatment outcomes for patients. Reducing the frequency of required administrations could improve adherence but is challenging for topical drug delivery due to the generally short residence time of topical formulations on the skin. In this study, we sought to determine the feasibility of developing a microbiome-based, long-acting, topical delivery platform using Bacillus subtilis for drug production and delivery on the skin, which was assessed using green fluorescent protein as a model heterologous protein for delivery. We developed a computational model of bacteria population dynamics on the skin and used its qualitative predictions to guide experimental design choices. Using an ex vivo pig skin model and a human skin tissue culture model, we saw persistence of delivered bacteria for multiple days and observed little evidence of cytotoxicity to human keratinocyte cells in vitro. Finally, using an in vivo mouse model, we found that the delivered bacteria persisted on the skin for at least 1 day during every-other-day application and did not appear to present safety concerns. Taken together, our results support the feasibility of using engineered B. subtilis for topical drug delivery.

Skin locations inference and body fluid identification from skin microbial patterns for forensic applications.

Given that microbiological analysis can be an alternative method that overcomes the shortcomings of traditional forensic technology, and skin samples may be the most common source of cases, the analysis of skin microbiome was investigated in this study. High-throughput sequencing targeting the V3-V4 region of 16S rRNA gene was performed to reveal the skin microbiome of healthy individuals in Guangdong Han. The bacterial diversity of the palm, navel, groin and plantar of the same individual was analyzed. The overall classification based on 16S rRNA gene amplicons revealed that the microbial composition of skin samples from different anatomical parts was different, and the dominant bacterial genus of the navel, plantar, groin and palm skin were dominated by Cutibacterium, Staphylococcus, Corynebacterium and Staphylococcus, respectively. PCoA analysis showed that the skin at these four anatomical locations could only be grouped into three clusters. A predictive model based on random forest algorithm showed the potential to accurately distinguish these four anatomical locations, which indicated that specific bacteria with low abundance were the key taxa. In addition, the skin microbiome in this study is significantly different from the dominant microbiome in saliva and vaginal secretions identified in our previous study, and can be distinguished from these two tissue fluids. In conclusion, the present findings on the community and microbial structure details of the human skin may reveal its potential application value in assessing the location of skin samples and the type of body fluids in forensic medicine.