Aging-related changes in the diversity of women's skin microbiomes associated with oral bacteria

Microbiomes other than the gut: inflammaging and age-related diseases

During the course of evolution, bacteria have developed an intimate relationship with humans colonizing specific body sites at the interface with the body exterior and invaginations such as nose, mouth, lung, gut, vagina, genito-urinary tract, and skin and thus constituting an integrated meta-organism. The final result has been a mutual adaptation and functional integration which confers significant advantages to humans and bacteria. The immune system of the host co-evolved with the microbiota to develop complex mechanisms to recognize and destroy invading microbes, while preserving its own bacteria. Composition and diversity of the microbiota change according to development and aging and contribute to humans' health and fitness by modulating the immune system response and inflammaging and vice versa. In the last decades, we experienced an explosion of studies on the role of gut microbiota in aging, age-related diseases, and longevity; however, less reports are present on the role of the microbiota at different body sites. In this review, we describe the key steps of the co-evolution between Homo sapiens and microbiome and how this adaptation can impact on immunosenescence and inflammaging. We briefly summarized the role of gut microbiota in aging and longevity while bringing out the involvement of the other microbiota.

Skin Microbiome as Years Go By

The skin microbial communities, i.e., the microbiota, play a major role in skin barrier function so must remain dynamic to adapt to the changes in the niche environment that occur across the different body sites throughout the human lifespan. This review provides an overview of the major alterations occurring in the skin microbiome (microbial and genomic components) during the various stages of life, beginning with its establishment in the first weeks of life through to what is known about the microbiome in older populations. Studies that have helped identify the factors that most influence skin microbiome function, structure, and composition during the various life stages are highlighted, and how alterations affecting the delicate balance of the microbiota communities may contribute to variations in normal physiology and lead to skin disease is discussed. This review underlines the importance of improving our understanding of the skin microbiome in populations of all ages to gain insights into the pathophysiology of skin diseases and to allow better monitoring and targeted treatment of more vulnerable populations.

Characteristics of healthy and androgenetic alopecia scalp microbiome: Effect of Lindera strychnifolia roots extract as a natural solution for its modulation

OBJECTIVE

The human scalp harbours a vast community of microbiotal mutualists. Androgenetic alopecia (AGA), the most common form of hair loss in males, is a multifactorial condition involving genetic predisposition and hormonal changes. The role of microflora during hair loss remains to be understood. After having characterized the scalp microbiota of 12 healthy male subjects and 12 AGA male subjects (D0), the aim of this investigation was to evaluate the capacity of Lindera strychnifolia root extract (LsR) to restore a healthy bacterial and fungal scalp microflora after 83 days (D83) of treatment.

MATERIAL AND METHODS

The strategy used was based on high-throughput DNA sequencing targeting the encoding 16S ribosomal RNA for bacteria and Internal Transcribed Spacer 1 ribosomal DNA for fungi.

RESULTS

Test analysis of relative abundance comparing healthy and AGA subjects showed a significant increase of Cutibacterim acnes (P < 0.05) and Stenotrophomonas geniculata (P < 0.01) in AGA subjects. AGA scalp condition was also associated with a significant (P < 0.05) decrease of Staphylococcus epidermidis relative abundance. A lower proportion of Malassezia genus in samples corresponding to AGA scalps and an increase of other bacterial genera (Wallemia, Eurotium) were also noted. At the species level, mean relative abundance of Malassezia restricta and Malassezia globosa were significantly lower (P < 0.05) in the AGA group. Eighty-three days of treatment induced a significant decrease in the relative abundance of C. acnes (P < 0.05) and S. geniculata (P < 0.01). S. epidermidis increased significantly (P < 0.05). At the same time, LsR treatment induced a significant increase in the proportion of M. restricta and M. globosa (P < 0.05).

CONCLUSION

Data from sequencing profiling of the scalp microbiota strongly support a different microbial composition of scalp between control and AGA populations. Findings suggest that LsR extract may be a potential remedy for scalp microbiota re-equilibrium.

The microbiome: an emerging key player in aging and longevity

Revolutionary advancements of high-throughput sequencing and metagenomic tools have provided new insights to microbiome function, including a bidirectional relationship between the microbiome and host aging. The intestinal tract is the largest surface in the human body that directly interacts with foreign antigens - it is covered with extremely complex and diverse community of microorganisms, known as the gut microbiome. In a healthy gut, microbial communities maintain a homeostatic metabolism and reside within the host in a state of immune tolerance. Abnormal shifts in the gut microbiome, however, have been implicated in the pathogenesis of age-related chronic diseases, including obesity, cardiovascular diseases and neurodegenerative diseases. The gut microbiome is emerging as a key factor in the aging process. In this review, we describe studies of humans and model organisms that suggest a direct causal role of the gut microbiome on host aging. Additionally, we also discuss sex-dimorphism in the gut microbiome and its possible roles in age-related sex-dimorphic phenotypes. We also provide an overview of widely used microbiome analysis methods and tools which could be used to explore the impact of microbiome remodeling on aging.

The Pathobiology of Skin Aging: New Insights into an Old Dilemma

Long considered both physiologic and inevitable, skin aging is a degenerative phenomenon whereby both intrinsic and environmental factors conspire to produce an authentic disease. The consequences of this disorder are many and varied, ranging from atrophy and fragility to defective repair to deficient immunity and vulnerability to certain infections. The pathobiologic basis for skin aging remains poorly understood. At a cellular level, stem cell dysfunction and attrition appear to be key events, and both genetic and epigenetic factors are involved in a complex interplay that over time results in deterioration of our main protective interface with the external environment. Past and current understanding of the cellular and molecular intricacies of skin aging provide a foundation for future approaches designed to thwart the aging phenotype. Herein, the authors provide a review of current insights into skin aging, including the mechanisms of skin aging, the role of stem cells in skin aging and the implications of skin aging for the microbiome and for the development of cancer. Conquest of the oft overlooked disease of skin aging should have broad implications that transcend the integument and inform novel approaches to retarding aging and age-related dysfunction in those internal organs that youthful skin was designed to envelop and safeguard.

Changes of the human skin microbiota upon chronic exposure to polycyclic aromatic hydrocarbon pollutants

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are of environmental and public health concerns and contribute to adverse skin attributes such as premature skin aging and pigmentary disorder. However, little information is available on the potential roles of chronic urban PAH pollutant exposure on the cutaneous microbiota. Given the roles of the skin microbiota have on healthy and undesirable skin phenotypes and the relationships between PAHs and skin properties, we hypothesize that exposure of PAHs may be associated with changes in the cutaneous microbiota. In this study, the skin microbiota of over two hundred Chinese individuals from two cities in China with varying exposure levels of PAHs were characterized by bacterial and fungal amplicon and shotgun metagenomics sequencing.

RESULTS

Skin site and city were strong parameters in changing microbial communities and their assembly processes. Reductions of bacterial-fungal microbial network structural integrity and stability were associated with skin conditions (acne and dandruff). Multivariate analysis revealed associations between abundances of Propionibacterium and Malassezia with host properties and pollutant exposure levels. Shannon diversity increase was correlated to exposure levels of PAHs in a dose-dependent manner. Shotgun metagenomics analysis of samples (n = 32) from individuals of the lowest and highest exposure levels of PAHs further highlighted associations between the PAHs quantified and decrease in abundances of skin commensals and increase in oral bacteria. Functional analysis identified associations between levels of PAHs and abundance of microbial genes of metabolic and other pathways with potential importance in host-microbe interactions as well as degradation of aromatic compounds.

CONCLUSIONS

The results in this study demonstrated the changes in composition and functional capacities of the cutaneous microbiota associated with chronic exposure levels of PAHs. Findings from this study will aid the development of strategies to harness the microbiota in protecting the skin against pollutants. Video Abstract.

Potential of Skin Microbiome, Pro- and/or Pre-Biotics to Affect Local Cutaneous Responses to UV Exposure

The human skin hosts innumerable microorganisms and maintains homeostasis with the local immune system despite the challenges offered by environmental factors such as ultraviolet radiation (UVR). UVR causes cutaneous alterations such as acute (i.e., sunburn) and chronic inflammation, tanning, photoaging, skin cancer, and immune modulation. Phototherapy on the other hand is widely used to treat inflammatory skin diseases such as psoriasis, atopic dermatitis, polymorphic light eruption and graft-versus-host disease (GvHD), as well as neoplastic skin diseases such as cutaneous T cell lymphoma, among others. Previous work has addressed the use of pro- and pre-biotics to protect against UVR through anti-oxidative, anti-inflammatory, anti-aging, anti-carcinogenic and/or pro-and contra-melanogenic properties. Herein, we discuss and share perspectives of the potential benefits of novel treatment strategies using microbes and pro- and pre-biotics as modulators of the skin response to UVR, and how they could act both for protection against UVR-induced skin damage and as enhancers of the UVR-driven therapeutic effects on the skin.

Effects of Fermented Oils on Alpha-Biodiversity and Relative Abundance of Cheek Resident Skin Microbiota

The skin microbiome is in a very close mutualistic relationship with skin cells, influencing their physiology and immunology and participating in many dermatological conditions. Today, there is much interest in cosmetic ingredients that may promote a healthy microbiome, especially postbiotics, mainly derived from fermented products. In the present work, we studied the effects on skin microbiota of new patented natural oils obtained by unique fermentation technology in vivo. Three fermented oils were evaluated: F-Shiunko (FS), F-Artemisia® (FA) and F-Glycyrrhiza® (FG). The active components were included as single active component or in combination (FSAG) in an emulsion system. A total of 20 healthy women were recruited, and skin microbiota from cheek were analyzed by mean of swab sampling at T0 and T1 (after 4 weeks of a one-day treatment). 16S sequencing revealed that the treatment with fermented oils improved microbiome composition and alpha-diversity. It was shown that higher biodiversity reflects in a healthier microbial ecosystem since microbial diversity decreases in the presence of a disease or due to aging. The treatment also resulted in a more “beneficial” and “younger” microbial community since a significant decrease in Proteobacteria and the increase in Staphylococcus were reported after the treatment with fermented oils.

Skin bacterial structure of young females in China: The relationship between skin bacterial structure and facial skin types

BACKGROUND

Skin microbiota are involved in the skin physiological functions and are also affected by the skin physiological characteristics.

OBJECTIVE

To better understand the skin microbial characteristics of facial cheek skin and the relationship with skin physiological characteristics.

METHODS

By bacterial 16S rRNA gene sequencing, the authors studied the facial cheek skin microbial characteristics of 85 cases of young women aged 18-25 years.

RESULTS

Healthy young woman's cheek skin bacterial composition was relatively stable. Dry skin has high bacterial diversity and richness, and oily skin has low bacterial diversity and richness. Cutibacterium was significantly enriched in oily skin and was significantly negatively correlated with other genera such as Streptococcus (r > 0.5). There were significant positive correlations among other genera of enrichment in dry and neutral skin such as Streptococcus and Rothia (r > 0.8). Skin sebum level was significantly negatively correlated with bacterial alpha diversity index. The combined abundance of Cutibacterium acnes and Staphylococcus epidermidis was significantly positively correlated with sebum secretion (r > 0.5).

CONCLUSIONS

The skin sebum secretion and bacterial interaction were the important factors driving the young females' cheek skin bacterial community structure.

Site-specific molecular analysis of the bacteriota on worn spectacles

Regularly touched surfaces are usually contaminated with microorganisms and might be considered as fomites. The same applies for spectacles, but only little is known about their microbial colonization. Previous cultivation-based analyses from our group revealed a bacterial load strongly dominated by staphylococci. To better account for aerotolerant anaerobes, slow growing and yet-uncultivated bacteria, we performed an optimized 16S rRNA gene sequencing approach targeting the V1-V3 region. 30 spectacles were swab-sampled at three sites, each (nosepads, glasses and earclips). We detected 5232 OTUs affiliated with 19 bacterial phyla and 665 genera. Actinobacteria (64%), Proteobacteria (22%), Firmicutes (7%) and Bacteroidetes (5%) were relatively most abundant. At genus level, 13 genera accounted for 84% of the total sequences of all spectacles, having a prevalence of more than 1% relative abundance. Propionibacterium (57%), Corynebacterium (5%), Staphylococcus (4%), Pseudomonas, Sphingomonas and Lawsonella (3%, each) were the dominant genera. Interestingly, bacterial diversity on the glasses was significantly higher compared to nosepads and earclips. Our study represents the first cultivation-independent study of the bacteriota of worn spectacles. Dominated by bacteria of mostly human skin and epithelia origin and clearly including potential pathogens, spectacles may play a role as fomites, especially in clinical environments.

Age-Related Variation of Bacterial and Fungal Communities in Different Body Habitats across the Young, Elderly, and Centenarians in Sardinia

Human body microbes interact with the host, forming microbial communities that are in continual flux during the aging process. Previous studies have mostly focused on surveying a single body habitat to determine the age-related variation in the bacterial and fungal communities. A more comprehensive understanding of the variation in the human microbiota and mycobiota across multiple body habitats related to aging is still unclear. To obtain an integrated view of the spatial distribution of microbes in a specific Mediterranean population across a wide age range, we surveyed the bacterial and fungal communities in the skin, oral cavity, and gut in the young, elderly, and centenarians in Sardinia using 16S rRNA gene and internal transcribed spacer 1 (ITS1) sequencing. We found that the distribution and correlation of bacterial and fungal communities in Sardinians were largely determined by body site. In each age group, the bacterial and fungal communities found in the skin were significantly different in structure. In the oral cavity, age had a marginal impact on the structures of the bacterial and fungal communities. Furthermore, the gut bacterial communities in centenarians clustered separately from those of the young and elderly, while the fungal communities in the gut habitat could not be separated by host age.IMPORTANCE Site-specific microbial communities are recognized as important factors in host health and disease. To better understand how the human microbiota potentially affects and is affected by its host during the aging process, the fundamental issue to address is the distribution of microbiota related to age. Here, we show an integrated view of the spatial distribution of microbes in a specific Mediterranean population (Sardinians) across a wide age range. Our study indicates that age plays a critical role in shaping the human microbiota in a habitat-dependent manner. The dynamic age-related microbiota changes we observed across multiple body sites may provide possibilities for modulating microbe communities to maintain or improve health during aging.

Revealing the secret life of skin - with the microbiome you never walk alone

The human skin microbiome has recently become a focus for both the dermatological and cosmetic fields. Understanding the skin microbiota, that is the collection of vital microorganisms living on our skin, and how to maintain its delicate balance is an essential step to gain insight into the mechanisms responsible for healthy skin and its appearance. Imbalances in the skin microbiota composition (dysbiosis) are associated with several skin conditions, either pathological such as eczema, acne, allergies or dandruff or non‐pathological such as sensitive skin, irritated skin or dry skin. Therefore, the development of approaches which preserve or restore the natural, individual balance of the microbiota represents a novel target not only for dermatologists but also for skincare applications. This review gives an overview on the current knowledge on the skin microbiome, the currently available sampling and analysis techniques as well as a description of current approaches undertaken in the skincare segment to help restoring and balancing the structure and functionality of the skin microbiota.

Altered microbiota composition reflects enhanced communication in 15q11-13 CNV mice

Autism spectrum disorder (ASD) is a complex and heterogeneous neurodevelopmental disorder. In addition to the core symptoms of ASD, many patients with ASD also show comorbid gut dysbiosis, which may lead to various gastrointestinal (GI) problems. Intriguingly, there is evidence that gut microbiota communicate with the central nervous system to modulate behavioral output through the gut-brain axis. To investigate how the microbiota composition is changed in ASD and to identify which microbes are involved in autistic behaviors, we performed a 16S rRNA gene-based metagenomics analysis in an ASD mouse model. Here, we focused on a model with human 15q11-13 duplication (15q dup), the most frequent chromosomal aberration or copy number variation found in ASD. Species diversity of the microbiome was significantly decreased in 15q dup mice. A combination of antibiotics treatment and behavioral analysis showed that neomycin improved social communication in 15q dup mice. Furthermore, comparison of the microbiota composition of mice treated with different antibiotics enabled us to identify beneficial operational taxonomic units (OTUs) for ultrasonic vocalization.

Segregation of age-related skin microbiome characteristics by functionality

Although physiological changes are the most evident indicators of skin aging by alteration of the skin’s structure and function, we question whether skin aging is also affected by the structure and assembly process of the skin microbiome. We analysed the skin microbiomes of 73 healthy Chinese women in two age groups (25–35 years old and 56–63 years old) using 16S rRNA gene amplicon sequencing; the overall microbiome structure was significantly different between the two age groups. An analysis using ecological theory to evaluate the process of microbial community assembly processes revealed that the microbiomes of the older group were formed under a greater influence of the niche-based process, with the network of microbes being more collapsed than that of the younger group. Inferred metagenomic functional pathways associated with replication and repair were relatively more predominant in the younger group whereas, among the various metabolism-related pathways, those associated with biodegradation were more predominant in the older group. Interestingly, we found two segregated sub-typing patterns in the younger group which were also observed in the skin microbiomes of young Chinese women living in four other cities in China. The results of our study highlights candidate microbes and functional pathways that are important for future research into preventing skin aging and which could lead to a comprehensive understanding of age-related skin microbiome characteristics.

Composition and diversity of the subgingival microbiome and its relationship with age in postmenopausal women: an epidemiologic investigation

BACKGROUND

The extent to which the composition and diversity of the oral microbiome varies with age is not clearly understood.

METHODS

The 16S rRNA gene of subgingival plaque in 1219 women, aged 53-81 years, was sequenced and its taxonomy annotated against the Human Oral Microbiome Database (v.14.5). Composition of the subgingival microbiome was described in terms of centered log(2)-ratio (CLR) transformed OTU values, relative abundance, and prevalence. Correlations between microbiota abundance and age were evelauted using Pearson Product Moment correlations. P-values were corrected for multiple testing using the Bonferroni method.

RESULTS

Of the 267 species identified overall, Veillonella dispar was the most abundant bacteria when described by CLR OTU (mean 8.3) or relative abundance (mean 8.9%); whereas Streptococcus oralis, Veillonella dispar and Veillonella parvula were most prevalent (100%, all) when described as being present at any amount. Linear correlations between age and several CLR OTUs (Pearson r = - 0.18 to 0.18), of which 82 (31%) achieved statistical significance (P < 0.05). The correlations lost significance following Bonferroni correction. Twelve species that differed across age groups (each corrected P < 0.05); 5 (42%) were higher in women ages 50-59 compared to ≥70 (corrected P < 0.05), and 7 (48%) were higher in women 70 years and older.

CONCLUSIONS

We identified associations between several bacterial species and age across the age range of postmenopausal women studied. Understanding the functions of these bacteria could identify intervention targets to enhance oral health in later life.

Staphylococcus epidermidis role in the skin microenvironment

Wound healing is a complex dynamic physiological process in response to cutaneous destructive stimuli that aims to restore the cutaneous' barrier role. Deciphering the underlying mechanistic details that contribute to wound healing will create novel therapeutic strategies for skin repair. Recently, by using state-of-the-art technologies, it was revealed that the cutaneous microbiota interact with skin immune cells. Strikingly, commensal Staphylococcus epidermidis-induced CD8+ T cells induce re-epithelization of the skin after injury, accelerating wound closure. From a drug development perspective, the microbiota may provide new therapeutic candidate molecules to accelerate skin healing. Here, we summarize and evaluate recent advances in the understanding of the microbiota in the skin microenvironment.

The prevalence of the culturable human skin aerobic bacteria in Riyadh, Saudi Arabia

Background

Human skin is an appropriate environment for the growth of different types of microbes that may inhabit the skin as commensal flora. This study aims at identifying the diversity of skin microbiota in healthy Saudi population. In this study, 80 Saudi subjects of both males and females, from different habitat, and different ages (elderly and young), were recruited to determine the aerobic bacterial flora from their three skin sites; hand, scalp and foot. A single colony obtained from aerobic culture was identified using Biomérieux VITEK® 2 system. For those not being identified by VITEK® 2 system, the identification was conducted using 16 s rRNA sequence.

Results

Thirty-three bacterial species were isolated from males, whilst 24 species were isolated from females. Micrococci are the predominant organisms, followed by Staphylococci, Pantoea species, and lastly Enterococcus faecium. Acinetobacter baumannii, Enterococcus faecalis, and Klebsiella pneumoniae were only found in elder subjects, while Pseudomonas aeruginosa was isolated from the young only. The number of bacterial isolates in the elders was higher that of the young. The average number of flora was larger in foot, then hand and lastly scalp.

Conclusion

Here we show the difference in the number of cultivable bacteria across age and gender that may result in the variety of local skin infection. This study paves the way to further investigation in the aspect of in-depth metagenomics analysis and host-pathogen interaction.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1569-5) contains supplementary material, which is available to authorized users.

Atopic dermatitis in the elderly: a review of clinical and pathophysiological hallmarks

BACKGROUND

Atopic dermatitis (AD) is a multifactorial and complex disease, characterized by an impaired skin barrier function and abnormal immune response. Many elderly patients present with pruritus and xerosis to dermatology, allergy and primary care clinics, and there is a lack of information available to clinicians regarding the proper diagnosis and management of these patients. Although the elderly are described as having a distinct presentation of AD and important comorbidities, most investigations and clinical care guidelines pertaining to AD do not include patients aged 60 years and older as a separate group from younger adults.

OBJECTIVES

To summarize current information on pathophysiology, diagnosis and management of AD in the elderly population and identify areas of insufficient information to be explored in future investigations.

METHODS

We carried out a systematic review of published literature, which assessed changes in the skin barrier and immune function with ageing and current information available for physicians to use in the diagnosis and treatment of AD in elderly patients.

RESULTS

Many age-related changes overlap with key hallmarks observed in AD, most notably a decline in skin barrier function, dysregulation of the innate immune system, and skewing of adaptive immunity to a type-2 T helper cell response, in addition to increased Staphylococcus aureus infection.

CONCLUSIONS

While general physiological alterations with ageing overlap with key features of AD, a research gap exists regarding specific ageing-related changes in AD disease development. More knowledge about AD in the elderly is needed to establish firm diagnostic and treatment methodologies. What's already known about this topic? Atopic dermatitis (AD) is a common inflammatory skin disease that causes significant burden worldwide. Recently, elderly patients have been considered a subgroup of patients with distinct AD manifestation. Limited studies have characterized the clinical presentation and role of IgE-mediated allergy in elderly patients with AD. What does this study add? This review offers a summary of age-related skin and immune alterations that correspond to pathogenic changes noted in patients with AD. The role of itch, environmental factors and skin microbiota in AD disease presentation in ageing patients is explored.

New Insights into the Intrinsic and Extrinsic Factors That Shape the Human Skin Microbiome

Many studies have highlighted the importance of body site and individuality in shaping the composition of the human skin microbiome, but we still have a poor understanding of how extrinsic (e.g., lifestyle) and intrinsic (e.g., age) factors influence its composition. We characterized the bacterial microbiomes of North American volunteers at four skin sites and the mouth. We also collected extensive subject metadata and measured several host physiological parameters. Integration of host and microbial features showed that the skin microbiome was predominantly associated with demographic, lifestyle, and physiological factors. Furthermore, we uncovered reproducible associations between chronological age, skin aging, and members of the genus Corynebacterium. Our work provides new understanding of the role of host selection and lifestyle in shaping skin microbiome composition. It also contributes to a more comprehensive appreciation of the factors that drive interindividual skin microbiome variation.

Despite recognition that biogeography and individuality shape the function and composition of the human skin microbiome, we know little about how extrinsic and intrinsic host factors influence its composition. To explore the contributions of these factors to skin microbiome variation, we profiled the bacterial microbiomes of 495 North American subjects (ages, 9 to 78 years) at four skin surfaces plus the oral epithelium using 16S rRNA gene amplicon sequencing. We collected subject metadata, including host physiological parameters, through standardized questionnaires and noninvasive biophysical methods. Using a combination of statistical modeling tools, we found that demographic, lifestyle, and physiological factors collectively explained 12 to 20% of the variability in microbiome composition. The influence of health factors was strongest on the oral microbiome. Associations between host factors and the skin microbiome were generally dominated by operational taxonomic units (OTUs) affiliated with the Clostridiales and Prevotella. A subset of the correlations between microbial features and host attributes were site specific. To further explore the relationship between age and the skin microbiome of the forehead, we trained a Random Forest regression model to predict chronological age from microbial features. Age was associated mostly with two mutually coexcluding Corynebacterium OTUs. Furthermore, skin aging variables (wrinkles and hyperpigmented spots) were independently correlated to these taxa.

Slowing Down Ageing: The Role of Nutrients and Microbiota in Modulation of the Epigenome

The human population is getting ageing. Both ageing and age-related diseases are correlated with an increased number of senescent cells in the organism. Senescent cells do not divide but are metabolically active and influence their environment by secreting many proteins due to a phenomenon known as senescence associated secretory phenotype (SASP). Senescent cells differ from young cells by several features. They possess more damaged DNA, more impaired mitochondria and an increased level of free radicals that cause the oxidation of macromolecules. However, not only biochemical and structural changes are related to senescence. Senescent cells have an altered chromatin structure, and in consequence, altered gene expression. With age, the level of heterochromatin decreases, and less condensed chromatin is more prone to DNA damage. On the one hand, some gene promoters are easily available for the transcriptional machinery; on the other hand, some genes are more protected (locally increased level of heterochromatin). The structure of chromatin is precisely regulated by the epigenetic modification of DNA and posttranslational modification of histones. The methylation of DNA inhibits transcription, histone methylation mostly leads to a more condensed chromatin structure (with some exceptions) and acetylation plays an opposing role. The modification of both DNA and histones is regulated by factors present in the diet. This means that compounds contained in daily food can alter gene expression and protect cells from senescence, and therefore protect the organism from ageing. An opinion prevailed for some time that compounds from the diet do not act through direct regulation of the processes in the organism but through modification of the physiology of the microbiome. In this review we try to explain the role of some food compounds, which by acting on the epigenetic level might protect the organism from age-related diseases and slow down ageing. We also try to shed some light on the role of microbiome in this process.

The role of the microbiome in scalp hair follicle biology and disease

The skin surface microbiome and its role in skin diseases have received increasing attention over the past years. Beyond, there is evidence for a continuous exchange with the cutaneous immune system in healthy skin, where hair follicles (HFs) provide unique anatomical niches. Especially, scalp HFs form large tubular invaginations, which extend deeply into the skin and harbour a variety of microorganisms. The distinct immunology of HFs with enhanced immune cell trafficking in superficial compartments in juxtaposition to immune-privileged sites crucial for hair follicle cycling and regeneration makes this organ a highly susceptible structure. Depending on composition and penetration depth, microbiota may cause typical infections, but may also contribute to pro-inflammatory environment in chronic inflammatory scalp diseases. Involvement in hair cycle regulation and immune cell maturation has been postulated. Herein, we review recent insights in hair follicle microbiome, immunology and penetration research and discuss clinical implications for scalp health and disease.

Effects of bowel preparation on the human gut microbiome and metabolome

Large bowel preparation may cause a substantial change in the gut microbiota and metabolites. Here, we included a bowel prep group and a no-procedure control group and evaluated the effects of bowel prep on the stability of the gut microbiome and metabolome as well as on recovery. Gut microbiota and metabolome compositions were analyzed by 16S rRNA sequencing and capillary electrophoresis time-of-flight mass spectrometry, respectively. Analysis of coefficients at the genus and species level and weighted UniFrac distance showed that, compared with controls, microbiota composition was significantly reduced immediately after the prep but not at 14 days after it. For the gut metabolome profiles, correlation coefficients between before and immediately after the prep were significantly lower than those between before and 14 days after prep and were not significantly different compared with those for between-subject differences. Thirty-two metabolites were significantly changed before and immediately after the prep, but these metabolites recovered within 14 days. In conclusion, bowel preparation has a profound effect on the gut microbiome and metabolome, but the overall composition recovers to baseline within 14 days. To properly conduct studies of the human gut microbiome and metabolome, fecal sampling should be avoided immediately after bowel prep.

Microbiome Dependent Regulation of Tregs and Th17 Cells in Mucosa

Mammals co-exist with resident microbial ecosystem that is composed of an incredible number and diversity of bacteria, viruses and fungi. Owing to direct contact between resident microbes and mucosal surfaces, both parties are in continuous and complex interactions resulting in important functional consequences. These interactions govern immune homeostasis, host response to infection, vaccination and cancer, as well as predisposition to metabolic, inflammatory and neurological disorders. Here, we discuss recent studies on direct and indirect effects of resident microbiota on regulatory T cells (T_regs) and Th17 cells at the cellular and molecular level. We review mechanisms by which commensal microbes influence mucosa in the context of bioactive molecules derived from resident bacteria, immune senescence, chronic inflammation and cancer. Lastly, we discuss potential therapeutic applications of microbiota alterations and microbial derivatives, for improving resilience of mucosal immunity and combating immunopathology.

Skin Changes During Ageing

The skin provides the primary protection for the body against external injuries and is essential in the maintenance of general homeostasis. During ageing, resident cells become senescent and the extracellular matrix, mainly in the dermis, is progressively damaged affecting the normal organization of the skin and its capacity for repair. In parallel, extrinsic factors such as ultraviolet irradiation, pollution, and intrinsic factors such as diabetes or vascular disease can further accelerate this phenomenon. Indeed, numerous mechanisms are involved in age-induced degradation of the skin and these also relate to non-healing or chronic wounds in the elderly. In particular, the generation of reactive oxygen species seems to play a major role in age-related skin modifications. Certainly, targeting both the hormonal status of the skin or its surface nutrition can slow down age-induced degradation of the skin and improve healing of skin damage in the elderly. Skin care regimens that prevent radiation and pollution damage, and reinforce the skin surface and its microbiota are among the different approaches able to minimize the effects of ageing on the skin.

A view to a kill? - Ambient bacterial load of frames and lenses of spectacles and evaluation of different cleaning methods

Surfaces with regular contact with the human body are typically contaminated with microorganisms and might be considered as fomites. Despite spectacles being widespread across populations, little is known about their microbial contamination. Therefore, we swab-sampled 11 worn spectacles within a university setting as well as 10 worn spectacles in a nursing home setting. The microbial load was determined by aerobic cultivation. All spectacles were found to be contaminated with bacteria, with nose pads and ear clips having the highest density, i.e. at sites with direct skin contact. Summed over all sites, the median microbial load of the university spectacles (1.4 ± 10.7 x 10(3) CFU cm-2) did not differ significantly from the spectacles tested in the nursing home (20.8 ± 39.9 x 10(3) CFU cm-2). 215 dominant bacterial morphotypes were analyzed by MALDI biotyping. 182 isolates could be assigned to 10 genera, with Staphylococcus being the most common. On genus-level, bacterial diversity was greater on nursing home spectacles (10 genera) compared to the university environment (2 genera). Four cleaning methods were investigated using lenses artificially contaminated with Escherichia coli, Micrococcus luteus, a 1:2 mixture of E. coli and M. luteus, and Staphylococcus epidermidis (the dominant isolate in our study), respectively. Best cleaning results (99% -100% median germ reduction) were obtained using impregnated wipes; dry cleaning was less effective (85% -90% median germ reduction). Finally, 10 additional worn university spectacles were cleaned with wipes impregnated with an alcohol-free cleaning solution before sampling. The average bacterial load was significantly lower (0.09 ± 0.49 x 10(3) CFU cm-2) compared to the uncleaned university spectacles previously investigated. Spectacles are significantly contaminated with bacteria of mostly human skin origin-including significant amounts of potentially pathogenic ones and may contribute to eye infections as well as fomites in clinical environments.

Minor taxa in human skin microbiome contribute to the personal identification

The human skin microbiome can vary over time, and inter-individual variability of the microbiome is greater than the temporal variability within an individual. The skin microbiome has become a useful tool to identify individuals, and one type of personal identification using the skin microbiome has been reported in a community of less than 20 individuals. However, identification of individuals based on the skin microbiome has shown low accuracy in communities larger than 80 individuals. Here, we developed a new approach for personal identification, which considers that minor taxa are one of the important factors for distinguishing between individuals. We originally established a human skin microbiome for 66 samples from 11 individuals over two years (33 samples each year). Our method could classify individuals with 85% accuracy beyond a one-year sampling period. Moreover, we applied our method to 837 publicly available skin microbiome samples from 89 individuals and succeeded in identifying individuals with 78% accuracy. In short, our results investigate that (i) our new personal identification method worked well with two different communities (our data: 11 individuals; public data: 89 individuals) using the skin microbiome, (ii) defining the personal skin microbiome requires samples from several time points, (iii) inclusion of minor skin taxa strongly contributes to the effectiveness of personal identification.

Shift in skin microbiota of Western European women across aging

AIMS

The objective of our study was to compare the microbiota diversity between two different age groups of Western European women.

METHODS AND RESULTS

Skin-swab samples were collected directly on the forehead of 34 healthy Western European women: 17 younger (21-31 years old) and 17 older individuals (54-69 years old). Bacterial communities were evaluated using the 16S rRNA gene sequencing. Data revealed a higher alpha diversity on the skin of older individuals compared with younger ones. Overall microbiota structure was different between the two age groups, as demonstrated by beta diversity analysis, which also highlighted a high interpersonal variation within older individuals. Furthermore, taxonomic composition analysis showed both an increase in Proteobacteria and a decrease in Actinobacteria on the older skin. At the genus level, older skin exhibited a significant increase in Corynebacterium and a decrease in Propionibacterium relative abundance.

CONCLUSIONS

Our study revealed a shift in the distribution of skin microbiota during chronological aging in Western European women.

SIGNIFICANCE AND IMPACT OF STUDY

Altogether these results could become the basis to develop new approaches aiming to rebalance the skin microbiota, which is modified during the aging process.