Staphylococcus aureus (S. aureus) increases at inflammation site of atopic dermatitis, and aggravates the inflammation. On the other hands, Staphylococcus epidermidis (S. epidermidis) is a common microbiota on healthy skin and has several beneficial functions such as suppression of S. aureus growth. This study evaluated antibacterial activity of many fatty acids against S. aureus and S. epidermidis. The results showed that 6-cis-C16:1, 7-cis-C16:1, and 9-cis-C16:1 possessed selective antibacterial activity that strongly suppressed S. aureus growth and weakly suppressed S. epidermidis growth, and the function may be beneficial for decrease inflammation at atopic dermatitis skin. The 6-cis-C16:1 included in skin lipids is rarely observed in natural oils, we thus investigated microbial-mediated production of 7-cis-C16:1 and 9-cis-C16:1. Aeromonas hydrophila and Acinetobacter sp. converted 9-cis-C18:1 to 7-cis-C16:1 when the strains were cultivated with vegetable oils. Genetic modified Saccharomyces cerevisiae produced triacylglycerols including high content 9-cis-C16:1, and the following purification processes resulted in 98% 9-cis-C16:1. Bifidobacterium sp. JCM 7042 produced 7-cis-C16:1 inside the cells.

In recent years, much progress has been made in research on human resident bacterial flora owing to the development of analysis equipment such as next-generation sequencers and improvements in sample processing technology. The entire picture of resident microbiota is being clarified not only with respect to the types and proportions of bacteria that constitute the microbiota but also the crosstalk between bacteria. Resident bacterial flora are deeply involved in human health; therefore, disruption of their balance and loss of diversity (dysbiosis) can cause poor health and disease. In this paper, we first explain the characteristics of each microbiota that forms in the intestine, oral cavity, and skin and discuss recent advances. We then present information on skin care and disease therapy based on regulation of the resident flora in the skin.

Sensitive skin has been stated as a syndrome defined by the occurrence of unpleasant sensations in response to stimuli that normally should not provoke such sensations. Significant prevalence of sensitive skin claim worldwide in both men and women has been resulting in quite a few skincare products in the market designed for sensitive skin, among which, however, almost none targets skin microbiome. Since accumulating evidence strongly indicate significant contribution of skin microbiome in the skin’s barrier function which could affect sensitive skin conditions, skin microbiome’s involvement in the sensitivity of skin is highly likely. This review summarizes the current studies around sensitive skin and skin microbiome.

Hydrolyzable tannins are a group of plant polyphenols consisting of a glucose core and acyl groups. Among them, ellagitannins have characteristic hexahydroxydiphenoyl and dehydrohexahydroxydiphenoyl groups as acyl groups. This review describes the chemical structures and stereochemistry of several hydrolyzable tannins, as well as their oxidative metabolism involved in ellagitannin biosynthesis.