Abstract
Several scalp microbiome studies from different populations have revealed the association of dandruff with bacterial and fungal dysbiosis. However, the functional role of scalp microbiota in scalp disorders and health remains scarcely explored. Here, we examined the bacterial and fungal diversity of the scalp microbiome and their potential functional role in the healthy and dandruff scalp of 140 Indian women. Propionibacterium acnes and Staphylococcus epidermidis emerged as the core bacterial species, where the former was associated with a healthy scalp and the latter with dandruff scalp. Along with the commonly occurring Malassezia species (M. restricta and M. globosa) on the scalp, a strikingly high association of dandruff with yet uncharacterized Malassezia species was observed in the core mycobiome. Functional analysis showed that the fungal microbiome was enriched in pathways majorly implicated in cell-host adhesion in the dandruff scalp, while the bacterial microbiome showed a conspicuous enrichment of pathways related to the synthesis and metabolism of amino acids, biotin, and other B-vitamins, which are reported as essential nutrients for hair growth. A systematic measurement of scalp clinical and physiological parameters was also carried out, which showed significant correlations with the microbiome and their associated functional pathways. The results point toward a new potential role of bacterial commensals in maintaining the scalp nutrient homoeostasis and highlights an important and yet unknown role of the scalp microbiome, similar to the gut microbiome. This study, therefore, provides new perspectives on the better understanding of the pathophysiology of dandruff.
Highlights
The scalp surface provides a distinct microenvironment to the microbes, primarily arising from the host physiological conditions, which include the sebum content, moisture, pH, and topography (Oh et al, 2014; Xu et al, 2016)
It was observed that the alpha-diversity (Shannon diversity index) for the fungal population was significantly lower (p ≤ 0.001) in the healthy scalp compared to the dandruff scalp (Figure 1A)
This study provides the first comprehensive overview of the scalp microbiome and its association with healthy and dandruff scalp using complementary high throughput sequencing approaches in a large human cohort
Summary
The scalp surface provides a distinct microenvironment to the microbes, primarily arising from the host physiological conditions, which include the sebum content, moisture, pH, and topography (Oh et al, 2014; Xu et al, 2016). The association of the prominent fungal and bacterial genera, more the association of Malassezia yeasts, with various scalp conditions has been reported frequently (Brüggemann et al, 2004; Deangelis et al, 2007; Otto, 2009; Clavaud et al, 2013; Magiatis et al, 2013; Grice and Dawson, 2017; Zhu et al, 2017). Their pathogenic role and potential as a causal agent remains unclear
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