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Studying the skin microbiome poses unique challenges, primarily due to the complexity of replicating its intricate environment in vitro. Recent innovations are addressing these limitations, enabling more precise, ethical and impactful microbiome research. What We Know: Skin microbiome research aims to uncover microbial traits and community dynamics associated with specific conditions or changes, providing a foundation for understanding host-microbe interactions. Microbes, highly sensitive to their environment, can serve as biomarkers for skin health, disease differentiation or treatment optimisation. These studies advance our knowledge of skin biology and support therapeutic innovation (Grogan et al., 2019) . Despite their value, many skin microbes are difficult to culture due to the complexity of the skin environment and the limitations of existing techniques. As a result, culture independent methods like 16S rRNA gene sequencing and shotgun metagenomics are widely used. These approaches analyse microbial DNA directly from samples, bypassing the need for cultivation (Grogan et al., 2019). While effective at profiling microbial ratios, culture-independent methods often lack insight into molecular interactions among microbes and with their host. A multi-omics approach - integrating metagenomics, metabolomics, proteomics and lipidomics - offers a more comprehensive way to study these complex interactions (Grogan et al., 2019). Industry Impact and Potential: A significant advancement in skin microbiome research is the TUS Skin Bacteria Co-culture (TSBC) medium, introduced by Yamamoto et al. (2024). This system enables the in vitro  study of four key skin microbes - Staphylococcus epidermidis, S. capitis, Cutibacterium acnes  and Corynebacterium  - by mimicking the skin’s natural environment. The TSBC medium has shown microbial ratios similar to those on Japanese skin, demonstrating its potential for broader applications. It facilitates research into how microbiota respond to internal factors, such as physiological changes, and external influences like skincare products (Yamamoto et al., 2024) . Together, culture-independent methods like metagenomic sequencing and culture-dependent systems like TSBC provide complementary tools for skin microbiome exploration. These advances open avenues for uncovering molecular interactions, developing targeted treatments, and enhancing personalized skincare solutions. Our Solution: Sequential is at the forefront of microbiome product testing and development, offering tailored solutions to help businesses innovate microbiome-focused products. Our expertise includes advanced culture-independent methods such as shotgun metagenomic sequencing, 16S rRNA profiling and ITS profiling, customised for diverse research needs. Whether exploring the skin, oral, scalp or vulvar microbiomes, Sequential is your ideal partner in unlocking the potential of microbiome research. References: Grogan, M.D., Bartow-McKenney, C., Flowers, L., Knight, S.A.B., Uberoi, A. & Grice, E.A. (2019) Research Techniques Made Simple: Profiling the Skin Microbiota. The Journal of investigative dermatology . 139 (4), 747-752.e1. doi:10.1016/j.jid.2019.01.024. Yamamoto, I., Sekino, Y., Kuramochi, K. & Furuyama, Y. (2024) Developing an In Vitro Culture Model for Four Commensal Bacteria of Human Skin .

Introduction The crucial role of the skin microbiome in aiding the development and maintenance of host cutaneous health and immunity has been gaining gradual recognition in the field of skin microbiome science (Liu et al. , 2023). From establishing immune tolerance in early life, to producing antimicrobial compounds to combat infection, and driving wound healing to prevent entry of unwanted pathogens past the skin barrier and into the body, it is becoming increasingly clear that these skin-associated microorganisms have a direct role in impacting host cell behaviour and function during immune development.  This is further revealed through the disruption of this balance between the two symbionts triggering infection and the development of skin disorders detrimental to host skin health. Recent studies have noted a rapid increase in the incidence of chronic inflammatory disorders like that of atopic dermatitis (AD) in recent years, with much of this through to be brought about as a result of modern lifestyle changes (i.e., increased hygiene and less exposure to microbes that enrich the microbiome) that fail to provide sufficient training for the immune system in developing these tolerogenic responses against inflammation (Alkotob et al. , 2020). Therefore, understanding and filling in our existing gaps in knowledge regarding the specifics of this immune-microbiome dialogue will be key to advancing the development of effective microbe-based treatments and therapies to address these problem areas and disorders. Study No. 1: Mechanisms of microbe-immune system dialogue within the skin (Lunjani et al.,  2021) This review article set out to outline the mechanisms through which microbes on the skin interact with each other, as well as discussing the systems that drive communication between the cutaneous microbiome and host immune system, in order to understand the role of such host-microbiome interactions in maintaining skin health (Lunjani et al. , 2021). Results Resident microbes were found to overproduce antimicrobial compounds in response to an overabundance of Staphylococcus aureus , a bacterial pathogen commonly associated with the skin disorder atopic dermatitis (AD), with beneficial, protective strains of staphylococci, such as S. epidermidis  and S. hominis , producing bacteriocin peptides to inhibit their growth by disrupting normal cell function. These species are also capable of producing other types of antimicrobial peptide that achieve similar results. The secretion of phenol-soluble modulins (PSMs) and proteases by S. Epidermidis  work by disrupting the cell membrane of these bacteria and inhibiting S. aureus biofilm formation, respectively. On the other hand, S. hominis  is capable of producing lantibiotics that are also capable of disrupting cellular membranes and preventing cell wall biosynthesis (Chakraborty, Gangopadhyay and Datta, 2019), while species such as S. lugdunensis  releases the peptide lugdunin to interrupt the usual bioelectrical activity of the cell membrane, preventing functions such as energy generation and communication (Benarroch and Asally, 2020) that allow S. aureus  to survive. Furthermore, the authors note S. aureus  has developed a complex system of communication that allows individual bacterial cells to detect and respond to changes in their local environment known as quorum sensing (Moreno-Gámez, Hochberg and van Doorn, 2023). In response, several species of commensal microbes are able to produce inhibitory molecules that block this signalling through quorum quenching, which is then able to block subsequent biofilm formation and enhance host immune response to infection. In addition to describing the complex ecological interactions mediating population control within these microbial communities on the skin, the authors of the paper also explored the mechanism of modulation of the host immune system by the cutaneous microbiome. Groups of specialised immune receptors present on the surface of skin cells of the epidermis (i.e., keratinocytes) are able to detect and distinguish between different microbe-identifying components such as proteins or genetic material, which allows the host immune system to regulate microbial density and community composition by preventing unwanted growth of potential pathogens through triggering the release of antimicrobials upon detection. Commensals on the skin are also capable of engaging in complex forms of communication with these keratinocytes to alert the host to any unwanted strains and triggering their defences. For example, the PSMs secreted by S. epidermidis  can also induce the production of keratinocyte-derived antimicrobial peptides and specific inflammatory molecules by activating some of the immune receptors present on these cells. However, these bacteria are just as capable of inhibiting a pro-inflammatory response by synthesising lipoteichoic acid following epithelial injury, which instructs these skin cells to increase the function of immune cells expressing immunoregulatory and tissue repair genes that block infection and repair the wounded skin. The authors also highlighted the role of other types of antimicrobial produced by resident skin commensals. Sapienic Acid is a type of fatty acid generated upon the metabolising of sebum by groups of bacteria, with deficient production of this compound associated with atopic dermatitis, possibly owing to its action against S. aureus , which is believed to be a risk factor for this condition. Cathelicidin, a peptide that works to disrupt the cell membranes of fungal and bacterial pathogens, as well as damaging the envelope of any infecting viral agents (Currie et al. , 2016). Anti-microbial histones, a component of neutrophil immune cells that can target and kill bacteria, as well as modulating the inflammatory immune response during infection both within the cell and outside in the extracellular environment. They are able to act against specific microorganisms like S. aureus, E. coli, and C. acnes  by inducing damage to their cellular membranes (Muñoz-Camargo and Cruz, 2024). Beyond this, the skin itself possesses a group of specialised Langerhans cells that are capable of sampling the environment for any unwanted microbes to trigger an immune response upon the detection of pathogen proteins. This property is also what allows them to produce an effective priming effect upon the host immune system for specific types of microbe such as C. albicans  and S. aureus , thus increasing the speed and effectiveness of response upon infection (Lunjani et al. , 2021). Conclusion The host-microbiome interface employs several molecular and chemical mechanisms to encourage effective communication between the two partners in the context of immune modulation in order to both protect the host from unwanted pathogen colonisation and infection, and defend against microbiome disruption and competition for resources. Such disruptions could lead to unwanted adverse effects, including accelerating the onset of certain dysbiosis-associated skin disorders such as atopic dermatitis, highlighting the importance of this bilateral immune dialogue in protecting the skin (Lunjani et al. , 2021). Study No. 2: Crosstalk between skin microbiota and immune system in health and disease (Liu et al., 2023) Introduction This comprehensive meeting report published by Nature  summarised the discussions of a workshop held by the US National Institute of Allergy and Infectious Diseases to evaluate the current state of knowledge regarding the interactions between skin microbial communities and the host immune system in health and disease (Liu et al. , 2023). Results The authors of this report noted microbial colonisation of the skin supports the establishment of immune tolerance in newborns via exposure to bacterial peptides and metabolites that induces the production of commensal-specific immune cells capable of recognising members of the host’s resident microbiota to avoid triggering unwanted immune responses targeting them for removal. Additionally, the presence of lipoteichoic acid in the cell walls of certain groups of bacteria bacteria may act to regulate the function of certain subsets of the host immune system by inducing the recruitment of maturation of immune mast cells into the skin (Wang et al. , 2017), while other strains such as S. epidermidis  are capable of producing a 6- N -hydroxyaminopurine compound that actively suppresses the growth of tumour cells and subsequent development of melanoma (Nakatsuji et al. , 2018). Several speakers also made mention of the role of certain skin microorganisms in the progression of atopic dermatitis, with some gene products from S. epidermidis  such as the enzyme cysteine protease (EcpA), promoting further inflammation and progressing disease severity, suggesting a role of certain species in driving further exacerbation of symptoms associated with certain skin disorders. Other detrimental effects associated with skin microbiome dysbiosis included the presence S. aureus  bacteria delaying the resolution of cutaneous lesions caused by infection with parasites belonging to the group Leishmania , hydrolase production by Malassezia  correlating with boosted production of proinflammatory cytokines from human skin cells, as well as a possible relationship between fungal dysbiosis and primary immune deficiencies such as STAT3 hyper IgE syndrome, a disorder characterised by eczema and recurrent skin infections (Tsilifis, Freeman and Gennery, 2021; Liu et al. , 2023). Conclusions Cross-talk between members of the cutaneous microbiome and their associated host are capable of driving both the establishment of immune tolerance, as well as shaping the development of host immune cells in early stages of life. Despite bringing about these beneficial effects, pathogenic behaviours of certain strains can also exacerbate the symptoms of dysbiotic skin disorders like atopic dermatitis, as well as interfering with regular functioning of the immune system, meaning a balance must be struck between the two to ensure skin function and homeostatic immunity (Liu et al. , 2023). Study No. 3: Skin autonomous antibody production regulates host–microbiota interactions (Gribonika et al.,  2024) Introduction This study sought to investigate the extent to which antibodies are involved in driving host skin immunity by studying the symbiotic mechanisms that trigger their production and mode of action in modulating host–microbiota dialogue and preventing onset of pathogenesis in a series of mouse models exposed to various immune treatments (Gribonika et al. , 2025). Results The authors of the study reported that topical association and colonisation of the skin by the commensal microbe S. epidermidis  was able to trigger the production of specific antibodies targeting this group of bacteria for density control, with signatures of these antibody responses detected within two weeks of administration and persisting for at least 200 days post-exposure, and followed by an increase in the level of S. epidermidis -specific antibody-secreting immune cells in the bone marrow 200 days post-topical association. This represents the development of an immune memory that is capable of producing commensal-specific antibodies targeting this specific species decades after initial exposure (Khodadadi et al. , 2019). These antibodies also demonstrated extreme strain-specificity, with no cross-reactions occurring between S. epidermidis -antibodies and other closely related species of skin bacteria such as Staphylococcus aureus . Further inoculating mice with groups of bacteria they had no prior exposure to (i.e., S. aureus  or Staphylococcus xylosus ) led to the production of antibodies specifically targeting these species, demonstrating the highly precise nature of these commensal-induced antibodies in matching their targets. Production of these topical microbe-specific antibodies were predicted to be driven by a need for the host to achieve control over the commensal burden by targeting a certain proportion of these bacteria for removal to ensure these microbes remain at a low biomass on the skin surface, as well as a general strategy to prevent infection by pathogens. To verify these claims, the researchers infected a group of mice with S. epidermidis  that they had not been previously exposed to and observed the growth of bacteria in these individuals 3 days post infection. In contrast, mice previously exposed to and already associated with this bacteria displayed a much more reduced bacterial presence in their tissues, which lends support to the idea of these commensal-specific antibodies playing a role in regulating population sizes of symbionts, with these effects observed more quickly in hosts already possessing a developed immunity against these commensals due to previous exposure to the same bacteria (Gribonika et al. , 2025). Conclusion Microbial colonisation and interaction with the skin is capable of priming the host immune system upon exposure into producing commensal-specific antibodies capable of selectively targeting and modulating the population sizes of skin resident species to reduce cutaneous microbiome biomass. These findings also highlight the role of the skin as an “autonomous lymphoid organ” capable of independently mounting an immune defensive response to regulate microbial infection and prevent any uncontrolled growth that could result in pathogenesis or infection (Gribonika et al. , 2025). Strengths & Limitations Strengths : Immunodeficient individuals that possess diminished antibody production capabilities have been shown to demonstrate increased susceptibility to skin infections. Further understanding the role of the microbiome in developing the skin’s immune system can have broad implications for the development of new therapies targeting the skin’s microbiome to help improve protection and immune development by leveraging the natural immune-priming properties of the skin microflora alongside its ability to secrete various compounds that protect the skin from disease (Gribonika et al. , 2025). Further research within this field can also foster the development of new technologies for the study of skin immunity such as: germ-free and gnotobiotic mice models, stem cells, and organoids. Not only that, but this might also aid progress in other fields of skin-related research beyond human immune system-skin microbiome interactions, extending to topics like skin physiological development or cutaneous responses to environmental stress (Liu et al. , 2023). Limitations : Many knowledge gaps still remain in skin microbiome research that must be filled to accelerate progression in developing these immune therapeutic technologies. This includes addressing topics such as the interaction dynamics between the skin microbiome and two major components of the human immune system (innate vs adaptive), how the immune system is capable of identifying and distinguishing between different commensal strains, and what the major cells and signalling pathways involved in this commensal-specific immune response are (Liu et al. , 2023). Other challenges that exist more broadly in the field of skin microbiome research also include developing realistic models that more accurately represent the process of commensal skin colonisation both on the skin and within its various niches (e.g., hair follicles), as well as further studying commensal bacteria-human cell interactions on its surface to better understand the mechanistic process underlying such immune dialogues (Liu et al. , 2023). Related Research and Future Directions Assessing the potential of topical pre- and probiotics for the treatment of skin disorders can help resolve much of the conflicting information in the current literature regarding the efficacy of such microbiome-based approaches in mitigating the effects of immune disorders of the skin. This can be taken further by investigating novel pre- and probiotic formulations that deviate from traditional ones by incorporating strains of bacteria and isolated metabolites that have not been previously used (Lunjani et al. , 2021). Further identification of new commensals and microbial metabolites that function in the skin microbiome environment could help build a more comprehensive understanding of the specific mechanisms by which the host immune system and cutaneous microbiome modulate each other to accelerate progress in therapeutic development to treat skin-associated disorders, as well as identifying novel targets for these treatments (Liu et al. , 2023). Conclusions The complex dialogue between the skin and its associated microbial community plays an important role in modulating host immunity and priming the host immune system against pathogen infection, all while promoting the selective recognition of symbiotic commensals through various means such as intercellular communication, antimicrobial peptide secretion, and commensal-specific antibody production. While previous studies offer detailed insight into some of the mechanisms employed during this symbiosis to confer cutaneous immunity, further studies might want to focus on developing knowledge gaps in other aspects of this area like the influence of these microbes over other components of the immune system (and vice-versa) to facilitate the development of novel therapeutics addressing skin health concerns by harnessing the natural immunogenic properties of the skin microbiome. References Alkotob, S.S. et al.  (2020) ‘Advances and novel developments in environmental influences on the development of atopic diseases’, Allergy , 75(12), pp. 3077–3086. Available at:   https://doi.org/10.1111/all.14624 . Benarroch, J.M. and Asally, M. (2020) ‘The Microbiologist’s Guide to Membrane Potential Dynamics’, Trends in Microbiology , 28(4), pp. 304–314. Available at:   https://doi.org/10.1016/j.tim.2019.12.008 . Chakraborty, H.J., Gangopadhyay, A. and Datta, A. (2019) ‘Prediction and characterisation of lantibiotic structures with molecular modelling and molecular dynamics simulations’, Scientific Reports , 9(1), p. 7169. Available at:   https://doi.org/10.1038/s41598-019-42963-8 . Cundell, A.M. (2018) ‘Microbial Ecology of the Human Skin’, Microbial Ecology , 76(1), pp. 113–120. Available at:   https://doi.org/10.1007/s00248-016-0789-6 . Currie, S.M. et al.  (2016) ‘Cathelicidins Have Direct Antiviral Activity against Respiratory Syncytial Virus In Vitro and Protective Function In Vivo in Mice and Humans’, The Journal of Immunology , 196(6), pp. 2699–2710. Available at:   https://doi.org/10.4049/jimmunol.1502478 . Gribonika, I. et al.  (2025) ‘Skin autonomous antibody production regulates host–microbiota interactions’, Nature , 638(8052), pp. 1043–1053. Available at:   https://doi.org/10.1038/s41586-024-08376-y . Khodadadi, L. et al.  (2019) ‘The Maintenance of Memory Plasma Cells’, Frontiers in Immunology , 10, p. 721. Available at:   https://doi.org/10.3389/fimmu.2019.00721 . Liu, Q. et al.  (2023) ‘Crosstalk between skin microbiota and immune system in health and disease’, Nature Immunology , 24(6), pp. 895–898. Available at:   https://doi.org/10.1038/s41590-023-01500-6 . Lunjani, N. et al.  (2021) ‘Mechanisms of microbe-immune system dialogue within the skin’, Genes & Immunity , 22(5), pp. 276–288. Available at:   https://doi.org/10.1038/s41435-021-00133-9 . Moreno-Gámez, S., Hochberg, M.E. and van Doorn, G.S. (2023) ‘Quorum sensing as a mechanism to harness the wisdom of the crowds’, Nature Communications , 14(1), p. 3415. Available at:   https://doi.org/10.1038/s41467-023-37950-7 . Muñoz-Camargo, C. and Cruz, J.C. (2024) ‘From inside to outside: exploring extracellular antimicrobial histone-derived peptides as multi-talented molecules’, The Journal of Antibiotics , 77(9), pp. 553–568. Available at:   https://doi.org/10.1038/s41429-024-00744-0 . Nakatsuji, T. et al.  (2018) ‘A commensal strain of Staphylococcus epidermidis protects against skin neoplasia’, Science Advances , 4(2), p. eaao4502. Available at:   https://doi.org/10.1126/sciadv.aao4502 . Tsilifis, C., Freeman, A.F. and Gennery, A.R. (2021) ‘STAT3 Hyper-IgE Syndrome—an Update and Unanswered Questions’, Journal of Clinical Immunology , 41(5), pp. 864–880. Available at:   https://doi.org/10.1007/s10875-021-01051-1 . Wang, Z. et al.  (2017) ‘Skin microbiome promotes mast cell maturation by triggering stem cell factor production in keratinocytes’, Journal of Allergy and Clinical Immunology , 139(4), pp. 1205-1216.e6. Available at:   https://doi.org/10.1016/j.jaci.2016.09.019 .

Emerging research into the oral-gut microbiome axis highlights the profound impact of these interconnected ecosystems on systemic health. Once considered distinct, the oral and gut microbiomes are now recognised for their influence on various health outcomes, opening new opportunities for innovation that optimises this relationship. What We Know: The oral cavity and gut, while separate, are linked through microbial migration, especially during dysbiosis or compromised gut barriers. Oral microbes can travel to the gut via oral-to-gut or faecal-to-oral routes, influenced by factors like low gastric acidity, poor hygiene and immune deficiencies (Park et al., 2021). Shared microbial taxa such as Streptococcus, Prevotella  and Veillonella  demonstrate this connection throughout the gastrointestinal tract (Kunath et al., 2024). Oral dysbiosis, often linked to periodontal disease, has widespread systemic effects. Pathogens like Porphyromonas gingivalis  and Fusobacterium nucleatum  contribute to conditions like inflammatory bowel disease (IBD), colorectal cancer (CRC), liver diseases and pancreatic cancer by promoting inflammation and disrupting gut barrier function (Park et al., 2021). Prolonged use of antibacterial mouthwash, like chlorhexidine, disrupts both the oral and gut microbiomes. A mouse study showed that chlorhexidine reduced weight gain and improved metabolic function, but also increased colon triglycerides, suggesting reduced nutrient absorption. While short-term effects were beneficial, potential long-term disruptions in microbiota balance and nutrient malabsorption highlight the need for careful formulation of oral care products. This illustrates the oral-gut microbiome axis' role (Carvalho et al., 2024). Industry Impact and Potential: Ongoing research is needed to clarify the complexities of the oral-gut microbiome axis. Advanced metagenomic studies will further our understanding of microbial interactions and their role in systemic diseases (Kunath et al., 2024). Microbiome therapies offer the potential for personalised medicine, targeting the oral-gut axis to treat conditions like IBD, CRC and autoimmune disorders. For example, probiotic interventions (Park et al., 2021). Oral microbiome analysis can also serve as a non-invasive, cost-effective tool for early disease detection, as science now knows this to be representative of a larger landscape (Park et al., 2021). Our Solution: At Sequential, we lead microbiome product development and testing from global hubs in London, New York and Singapore. Our customisable services empower businesses to innovate confidently, ensuring products preserve microbiome integrity while meeting efficacy and sustainability goals, and studies that explore this. Partner with us to explore optimising the oral-gut microbiome axis by oral microbiome intervention and develop cutting-edge solutions for improved health outcomes. References: Carvalho, L.R.R.A., Boeder, A.M., Shimari, M., Kleschyov, A.L., Esberg, A., Johansson, I., Weitzberg, E., Lundberg, J.O. & Carlstrom, M. (2024) Antibacterial mouthwash alters gut microbiome, reducing nutrient absorption and fat accumulation in Western diet-fed mice. Scientific Reports. 14 (1), 4025. doi:10.1038/s41598-024-54068-y. Kunath, B.J., De Rudder, C., Laczny, C.C., Letellier, E. & Wilmes, P. (2024) The oral–gut microbiome axis in health and disease. Nature Reviews Microbiology. 22 (12), 791–805. doi:10.1038/s41579-024-01075-5. Park, S.-Y., Hwang, B.-O., Lim, M., Ok, S.-H., Lee, S.-K., Chun, K.-S., Park, K.-K., Hu, Y., Chung, W.-Y. & Song, N.-Y. (2021) Oral-Gut Microbiome Axis in Gastrointestinal Disease and Cancer. Cancers. 13 (9), 2124. doi:10.3390/cancers13092124.

Discover our team of award-winning scientists dedicated to advancing microbiome research for a healthier world. Explore our expertise now. We are a Team of Award-Winning Scientists Creating a World with Healthier Microbiomes Our platform is the result of our team’s combined expertise in genetics, epigenetics, and microbiome research. We utilise deep molecular analysis and next-generation sequencing (NGS) technology to understand the impact of product usage on an individual’s microbiome. Through our efforts, we hope to revolutionise the way in which the industry develops and tests its products to deliver optimal results to those utilising them. Our Mission Sequential is the industry leader in clinical microbiome research and testing offering a comprehensive end-to-end platform designed to bring science-backed solutions to the personal care and pharmaceutical industry. Our mission is to understand the impact of the microbiome on the host (humans) and how the host impacts the microbiome in order to characterise human health fully. We offer an extensive platform to conduct research on personal care products through microbiome testing, and biophysical assessments, and offer full recruitment services for studies. We are keen to publish our findings with our partners to increase the literature within this space. At present our database of over 20,000 human microbiome samples is one of the most sophisticated within the industry and is growing rapidly. Innovation Pioneering the forefront of biological science, we consistently introduce groundbreaking advancements to redefine industry standards. Transparency Our commitment to openness ensures a clear understanding of our human microbiome testing processes and analysis. Reliability We guarantee dependable results, fostering trust in the accuracy of our analyses. Our Team at Sequential Dr. Oliver Worsley CHIEF EXECUTIVE OFFICER & CO-FOUNDER Oliver is the co-founder and CEO of Sequential. He completed his PhD in molecular genetics as a scholar at the Genome Institute of Singapore from 2014-2018, and has won multiple awards including the P&G Young Entrepreneurship Scheme, presented at the Royal Society in London in 2017; and the top prize at the L’Oréal Innovation Runway 2018. Oliver has previously founded Anya Consulting, a healthcare communications company that has published >150 articles and has produced several technical whitepapers for clients like Fierce Health. Prior, Oliver completed his BSc at Edinburgh University, including six months at Leiden University Medical Centre through the Erasmus Programme. Sibora Peca CLINICAL OPERATIONS LEAD Grace Robinson ASSOCIATE SCIENTIST Omololu Fagunwa SENIOR BIOINFORMATICIAN Amber Eades STRATEGIC PARTNERSHIPS LEAD Dr. Albert Dashi CHIEF SCIENCE OFFICER & CO-FOUNDER Albert is the co-founder and CSO of Sequential. He completed his PhD in molecular genetics, epigenetics and stem cell research at the National University of Singapore (NUS) and the Genome Institute of Singapore in 2019. In 2014, he received the Singapore International Graduate Award from A*STAR for his PhD research and was also awarded the “Young Investigator” award. He also won the “Young Entrepreneur Scheme” award by P&G for his innovative and business driven ideas. Prior moving to Singapore for his doctor program, Albert obtained his Masters in Biomedical Sciences at University of Bern, Switzerland. Andrew Davis SENIOR BIOINFORMATICIAN Forest Wong SENIOR LAB TECHNICIAN Shalindri Jayawardene RESEARCH ASSOCIATE Bindu Priyanka RESEARCH ASSOCIATE Petronille Houdart, PharmD SKINCARE DIRECTOR Petronille is Sequential's lead skincare director, focused on translating the latest in skin science to personalised skincare recommendations. She has over a decade in the industry, working with international brands to lead and consult on R&D, creative projects and brand innovation. Petronille also led her own award-winning dermocosmetic brand, Petronille Dermo Cosmetic, that produced customisable products for men and women. Petronille holds an MSc in Cosmetology Sciences and a professional doctorate in pharmacy (specialising in dermo-pharmacy) from Paris Descartes University. Marya Sheikh-Ahmed SENIOR MARKETING ASSOCIATE Dr. Sija Sajibu RESEARCH ASSOCIATE Ashley LaSalle JUNIOR LAB TECHNICIAN Michal Merav RESEARCH ASSOCIATE Please find listed a selection of relevant peer-reviewed publications from our advisors. Wu G, TL Dawson, et al. (2015) Genus-Wide Comparative Genomics of Malassezia Delineates Its Phylogeny, Physiology, and Niche Adaptation on Human Skin. PLOS Genetics 11(11): e1005614. Chng, K., Nagarajan, N., et al. (2016) Whole metagenome profiling reveals skin microbiome-dependent susceptibility to atopic dermatitis flare. Nat Microbiol 1, 16106. Tay, A.S., Nagarajan, N., et al (2018). 1039 Skin microbiome profiles of atopic dermatitis patients segregate into two community composition types that are stable before and after therapy. Journal of Investigative Dermatology. 138. S176. 10.1016/j.jid.2018.03.1051. Ramasamy S., Barnard, E., Dawson, TL, and Huiying Li. (2019). Role of the skin microbiota in acne pathophysiology. British Journal of Dermatology, https://doi.org/10.1111/bjd.18230. Dawson, TL. (2019) Malassezia: The Forbidden Kingdom Opens. Cell Host Microbe https://doi.org/10.1016/j.chom.2019.02.010 Tay, A.S., Nagarajan, N., et al (2020). Atopic dermatitis microbiomes stratify into ecologic dermotypes enabling microbial virulence and disease severity. The Journal of allergy and clinical immunology. 10.1016/j.jaci.2020.09.031. Dawson, TL. (2021) Malassezia: A Skin Commensal Yeast Impacting Both Health and Disease. Front. Cell. Infect. Microbiol., doi.org/10.3389/fcimb.2021.659219 Bissonnette, Robert & FAAD, & Palijan, Ana & Salem, Youssef & Maari, Catherine & Proulx, Etienne & Edjekouane, Lydia & Joly-Chevrier, Maxine & Devis, Andrew & Dashi, Albert & Worsley, Oliver. (2024). 50694 Gut microbiome differences between patients with moderate to severe Chronic Hand Eczema and healthy subjects. Journal of the American Academy of Dermatology. 91. AB224. 10.1016/j.jaad.2024.07.889. Supported By Scientific Board of Advisors Our advisors are world leaders in the skin microbiome and have extensive experience in bringing forward solutions for skin concerns Prof. Tom Dawson Senior Principal Investigator at Skin Research Institute of Singapore. Over 30 years experience in biotechnology innovations, and expert in the skin and hair microbiome. Doctor of Philosophy (PhD), Pharmacology at the Univer sity of North Carolina. Dr Kimberly Capone Dr Kimberly Capone is a pioneer and established expert in microbiology and the human microbiome field where she created new business opportunities across multiple brands over 13 years at Johnson & Johnson Consumer, Inc. Areas of concentration included infant and adult skin, vaginal, gut, and oral health. Prof. Phillip Bennett Phillip Bennett is Professor of Obstetrics and Gynaecology and Director of the Institute of Reproductive and Developmental Biology. Professor Bennett has been one of the key pioneers in researching the vaginal microbiome. In particular, to understand and characterise the impact of the vaginal microbiome on preterm labour. Bennett has published over 400 peer-reviewed research articles over his career. Dr Natalya Fox Dr Natalya Fox is a Dermatologist at the NHS - St George's Hospital, London. Previously, Fox did her MBChB at the University of Edinburgh 201 4 and has her Full MRCP UK in Dermatology. Fox is passionate about the skin microbiome and its place in dermatology. Prof. Elena Lurie-Luke A senior R&D, Innovation and Entrepreneurship Executive with extensive technical, strategic business development. Proven leadership experience in both global FMCG and public health sector environments. Prof. Niranjan Nagarajan Associate Director & Senior Group Leader at Genome Institute of Singapore. Expert in computation biology, in particular the study of microbial communities resident on the human skin. Doctor of Philosophy (PhD), Computer Science at Cornell University. Dr Alexander Lezhava Senior Group Leader & Associate Director at Genome Institute of Singapore. Expert in the commercial development of medical diagnostics and clinical-grade molecular assays. Doctor of Philosophy (PhD), Microbiology at Hiroshima University. Our Labs Sequential has microbiome testing labs in New York City, London and Singapore. Being close to our customers has allowed us to reduce turnaround time, whilst retaining the intellectual property in-house. Proud to Have Worked With

Seeking formulation support? Embark on the journey to your next best-selling product with our assistance. Let's collaborate and create success together! Create Your Next Best-Selling Formulation A well-designed formulation takes into account the diverse and delicate ecosystem of the microbiome. By incorporating ingredients that promote a harmonious relationship with the microbiota, such as prebiotics and postbiotics, a product can positively impact the microbial diversity and balance on the body. Having collected over 20,000+ human skin microbiome samples through in vivo clinical research, we can help you take your product from conception to completion. Consultation Book a consultation to start creating your microbiome supporting formulation. Whether you need help starting out or are already in the midst of your process, we can support you. INCI List Examination Have an INCI list and are unsure if it will be a formula? No need to look further, we will gladly look through your proposed INCI list and revert back with feedback. Co-Develop Let us be your Chief Science Officer, or your scientific advisory, and leverage our dataset for the co-development of products that suit your demographic and application. SKINCARE FORMULATIONS Regular to Atopic Skin, Start Formulating Today! What Contributes to a Microbiome Supporting Formulation? When creating a product that "maintains the microbiome", it is crucial to understand that every ingredient used is important. Hero ingredient-led philosophy cannot be applied in the formulation process as it is the blend of each ingredient that will create a product to support and improve the balance of the skin microbiome. Fermented ingredients (postbiotics) and those that act as food for microbes (prebiotics) are also known to have a positive impact on formulations when paired with the right preservative systems, surfactants, emollients, etc. It is still rare to find live bacteria (probiotics) in formulations, however, if encapsulated correctly, it could show improvement in the microbiome balance. Prebiotics Prebiotics beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria on the skin, and thus improves host health. Prebiotics act as food for the microbes on the skin, and allow good bacteria to grow and thrive. Probiotics Probiotics are living microorganisms that confer benefit to the host when applied to the body. Because probiotics are live bacteria, it is incredibly difficult to preserve and put into skincare products (especially when skincare contains preservatives). In fact, some products on the market that say they use probiotics, are actually using prebiotics or postbiotics. Postbiotics Postbiotics are the byproduct of fermented live bacteria (probiotics) or inactivated microorganisms. The process of fermentation releases nutrients inside of the bacteria and holds concentrated and nourishing skin health benefits that help to balance the skin microbiome. INGREDIENTS FROM MICROBIAL ORIGIN No INTENDED TO BE UTILISED BY THE HUMAN MICROBIOTA? No Yes Yes ARE THEY VIABLE? No Yes ORIGIN VIABILITY FUNCTION ORDINARY INGREDIENT ORDINARY INGREDIENT WITH PREBIOTIC FUNCTION INTENDED TO BE UTILISED BY THE HUMAN MICROBIOTA? PROBIOTIC INGREDIENT No POSTBIOTIC INGREDIENT Yes POSTBIOTIC INGREDIENT WITH PREBIOTIC FUNCTION Our Leading Expert & Skincare Director Pétronille Houdart A pharmacist by training, Pétronille specialized in dermo pharmacy and cosmetology. She has garnered extensive experience in the formulation of cosmetic products and is passionate about skincare. She started her career working for a private-label contract manufacturer that focused on custom cosmetic formulations for clients ranging from big brands to private dermatologist products. She has previously created a high-performance customisable formulation brand and is vocal about bespoke and innovative cosmetic formulations. Request a Consultation Ashfi Rahman, Co-founder at HonestStory "Sequential gave us completely essential consulting work on microbiome skincare formulations. They are the only company out there that combines their knowledge of microbiome testing with formulation expertise, and we're very happy to be working with them to develop the first microbiome skincare in India." FAQ What is Sequential's testing platform? Sequential has developed the gold standard test for microbiome-friendly products, in vivo (in, or on, humans). Finally, we can give some certainty about if a product is truly affecting the microbiome. We offer a complete end-to-end solution to support microbiome-friendly claims. From consultancy and study design to our proprietary microbiome testing kits. We analyse, interpret and report our findings to meet your needs. Why is it necessary to test the microbiome in vivo? At present, there are no regulations for microbiome-related formulas that brands and formulators can follow, however, it has been universally acknowledged that the in vivo method of conducting clinical studies is becoming critical and paramount to getting marketing claims through. When regulations are introduced, which may be imminent, the in vitro system will find itself lacking, resulting in limited claims and certifications that do not hold their value. This is why, we at Sequential strive to offer an in vivo approach, knowing full well that we want our client's claims to be significantly backed by scientific and quantifiable data. What type of sequencing technology does Sequential use for analysis? We offer four types of sequencing techniques including qPCR with our Smart Probes™, 16S, ITS and Shotgun Metagenomics. Using next-generation sequencing of the collection of microorganisms found on the body, during product usage, Sequential investigates the microbial diversity, and particular microorganisms we know are important and play a role in a healthy microbiome. Does Sequential offer claims certification for tested products? We provide our clients with a certification to claim “Maintains the Microbiome” subject to in vivo testing results which can be used in communication efforts. Once your product is tested with our qPCR Smart Probes™ and has shown favourable results in supporting the microbiome, we can certify your product with our Maintains the Microbiome certification seal. We have ensured that our seal and certification are backed by quantifiable data and scientifically significant markers. The aim is to ensure our clients feel confident in making their claims and can communicate the true benefit of their microbiome formulations.

Sequential provides advanced microbiome testing for personal care products, delivering actionable insights to enhance product efficacy and consumer trust. Your Clinical Microbiome Testing Partner A trusted leader in microbiome testing and research for the personal care industry, Sequential provides cutting-edge solutions to elevate product development. Our extensive microbiome research delivers effective and actionable insights, empowering brands to create innovative, science-backed personal care products that meet consumer demands and set new standards in the market. View Services Brochure 20,000+ Microbiome Sample Database 4,000+ Ingredient Database 10,000+ Testing Participants Globally 60+ Industry Partners Who We Are Sequential is a leading provider of clinical microbiome analysis and microbiome testing services, offering a comprehensive end-to-end platform with science-backed solutions tailored for the personal care and pharmaceutical industries. Our team of award-winning scientists is dedicated to understanding the intricate relationship between the microbiome and its human host, exploring how the microbiome impacts human health and how humans, in turn, influence their microbiome. This holistic approach enables us to fully characterise human health and provide actionable insights for product innovation and efficacy. Learn More What We Offer Microbiome Testing A fully customizable microbiome study to test your product's impact in a real-life context. Formulation Support Allow our formulation experts to guide you through the process of creating a product that maintains the biome. Claims & Certification Test your formulation to understand what marketing claims you can attribute to your product. Strategic Partnerships Join us in full end-to-end partnership (testing to collaborating on white papers). Clinical Assessments Understand your product's impact on transepidermal water loss, pH, and elasticity. Study Recruitment Let us recruit candidates and carry out in-lab testing for your study to ensure controlled collection. Our Testing Capabilities Differentiate your brand by leveraging the power of skin microbiome science to deliver innovative, research-backed personal care products. Stand out from competitors with solutions supported by robust clinical research and gold-standard microbiome certification, appealing to customers seeking credible and cutting-edge personal care innovations. Harness the science of the microbiome to build trust, drive customer loyalty, and position your brand as a leader in the personal care industry. What Our Clients Say “Sequential is one of the world’s most innovative Microbiome companies. The resolution at subspecies level, and to perform quantification of key vaginal microbes, in vivo , was exactly what we wanted at Curive Healthcare to know intricately how our product is working to improve women’s health.” - Matthew Line, Chief Marketing Officer at Curive Healthcare Supporting World-Class Clients & Partners Join Our Partners! Microbiome's Impact on Human Health Mechanisms of Microbe-Immune System Dialogue Within the Skin It’s All Connected: What Does the Oral-Gut Microbiome Axis Mean for Overall Health? Menstrual Products and the Microbiome: What Are the Effects on Vaginal Health? Read More Articles FAQ What is Sequential's testing platform? Sequential has developed the gold standard test for microbiome-friendly products, in vivo (in, or on, humans). Finally, we can give some certainty about if a product is truly affecting the microbiome. We offer a complete end-to-end solution to support microbiome-friendly claims. From consultancy and study design to our proprietary microbiome testing kits. We analyse, interpret and report our findings to meet your needs. Why is it necessary to test the microbiome in vivo? At present, there are no regulations for microbiome-related formulas that brands and formulators can follow, however, it has been universally acknowledged that the in vivo method of conducting clinical studies is becoming critical and paramount to getting marketing claims through. When regulations are introduced, which may be imminent, the in vitro system will find itself lacking, resulting in limited claims and certifications that do not hold their value. This is why, we at Sequential strive to offer an in vivo approach, knowing full well that we want our client's claims to be significantly backed by scientific and quantifiable data. What type of sequencing technology does Sequential use for analysis? We offer four types of sequencing techniques including qPCR with our Smart Probes™, 16S, ITS and Shotgun Metagenomics. Using next-generation sequencing of the collection of microorganisms found on the body, during product usage, Sequential investigates the microbial diversity, and particular microorganisms we know are important and play a role in a healthy microbiome. Does Sequential offer claims certification for tested products? We provide our clients with a certification to claim “Maintains the Microbiome” subject to in vivo testing results which can be used in communication efforts. Once your product is tested with our qPCR Smart Probes™ and has shown favourable results in supporting the microbiome, we can certify your product with our Maintains the Microbiome certification seal. We have ensured that our seal and certification are backed by quantifiable data and scientifically significant markers. The aim is to ensure our clients feel confident in making their claims and can communicate the true benefit of their microbiome formulations.