Shaping of cutaneous function by encounters with commensals

Abstract

The skin is the largest organ in the human body and provides the first line of defence against environmental attack and pathogen invasion. It harbor multiple commensal microbial communities at different body sites, which play important roles in sensing the environment, protecting against colonization and infection of pathogens, and guiding the host immune system in response to foreign invasions. The skin microbiome is largely variable between individuals and body sites, with several core commensal members commonly shared among individuals at the healthy state. These microbial commensals are essential to skin health and can potentially lead to disease when their abundances and activities change due to alterations in the environment or in the host. While recent advances in sequencing technologies have enabled a large number of studies to characterize the taxonomic composition of the skin microbiome at various body sites and under different physiological conditions, we have limited understanding of the microbiome composition and dynamics at the strain level, which is highly important to many microbe-related diseases. Functional studies of the skin microbial communities and the interactions among community members and with the host are currently scant, warranting future investigations. In this review, we summarize the recent findings on the skin microbiome, highlighting the roles of the major commensals, including bacteria, fungi and bacteriophages, in modulating skin functions in health and disease. Functional studies of the skin microbiota at the metatranscriptomic and proteomic levels are also included to illustrate the interactions between the microbiota and the host skin.

The balance of metagenomic elements shapes the skin microbiome in acne and health

“…The skin harbors several hundreds of resident microorganisms, which function in communities and protect the body from invasion of pathogens12. Several studies have shown that shifts in the skin microbiota are associated with various skin diseases34567.…”

Modulation of behaviour and virulence of a high alginate expressing Pseudomonas aeruginosa strain from cystic fibrosis by oral commensal bacterium Streptococcus anginosus

“…On a living host multispecies biofilms occur throughout the body, playing an important role in maintaining health and in disease pathogenesis [3,4,5,6,7]. Our increased awareness of the polymicrobial nature of many diseases has been due in no small way to the availability of culture-independent community analysis methodologies [8,9,10].…”

The role of the skin microbiota in acne pathophysiology

“…A complex milieu of interactions between skin and its commensal microflora safeguards skin from day‐to‐day environmental influence. However, occasionally, because of imbalanced relationships, the skin commensal microbiota may shift to harmful communities in noninfectious skin‐related pathologies such as atopic dermatitis, psoriasis, rosacea and acne . This imbalance is thought to potentiate epithelial dysfunction, immune dysregulation, or overgrowth of pathogenic microbes, and may in the near future impact how we address skin pathology and disease.…”

“…Present in both healthy and diseased skin, their roles as commensals or opportunistic organisms are not yet fully understood . For example, S. epidermidis produces antimicrobial peptides, while C. acnes produces antimicrobial short‐chain fatty acids, both of which function together with the host innate defence mechanisms to maintain skin health and homeostasis . However, these microbial species are also found in opportunistic infections, especially S. epidermidis , which is a causative agent of hospital‐acquired infections .…”

“…However, occasionally, because of imbalanced relationships, the skin commensal microbiota may shift to harmful communities in noninfectious skin-related pathologies such as atopic dermatitis, psoriasis, rosacea and acne. [19][20][21] This imbalance is thought to potentiate epithelial dysfunction, immune dysregulation, or overgrowth of pathogenic microbes, and may in the near future impact how we address skin pathology and disease. Gram-positive bacteria Staphylococcus epidermidis and C. acnes, and fungal species (predominately Malassezia) are the predominant residents on human epithelia and in sebaceous follicles.…”