Age-related changes in the bacterial composition of healthy female facial skin in Beijing area.

OBJECTIVE: Exploring the effects of age on microbial community structure and understanding the effects of chronological ageing as well as sun exposure on microbial community diversity. METHOD: The microbial characteristics of the facial skin of 98 adult women aged 18-70 years were studied using 16S rRNA gene sequencing, and differences based on age and reported sun exposure were assessed. RESULTS: The cheek skin's bacterial diversity and richness increased with age. The relative abundance of Cutibacterium decreased with age, while the relative abundance of Corynebacterium, Anaerococcus, Paracoccus, Micrococcus, Kocuria, Kytococcus, and Chryseobacterium increased. In addition, an increase in Micrococcus and a decrease in Cutibacterium were observed in volunteers with more than 2 h of daily sun exposure compared to volunteers with <2 h of daily sun exposure. Under low-sunlight conditions, Cutibacterium was more prevalent in the youth group, and Corynebacterium, Anaerococcus, and Kytococcus were more prevalent in the older group. CONCLUSION: The diversity and composition of the bacterial community on the cheeks are affected by age and extrinsic factors (sun exposure) may also play a role in this.

OBJECTIF: Étudier les effets de l'âge sur la structure de la communauté microbienne et comprendre les effets du vieillissement chronologique ainsi que de l'exposition au soleil sur la diversité de la communauté microbienne. MÉTHODE: Les caractéristiques microbiennes de la peau du visage de 98 femmes adultes âgées de 18 à 70 ans ont été étudiées à l'aide du séquençage génétique de l'ARNr 16S, et les différences basées sur l'âge et l'exposition au soleil rapportée ont été évaluées. RÉSULTAT: La diversité et la richesse bactériennes de la peau des joues ont augmenté avec l'âge. L'abondance relative de Cutibacterium a diminué avec l'âge, tandis que l'abondance relative de Corynebacterium, Anaerococcus, Paracoccus, Micrococcus, Kocuria, Kytococcus et Chryseobacterium a augmenté. De plus, une augmentation de Micrococcus et une diminution de Cutibacterium ont été observées chez des volontaires ayant été exposés au soleil pendant plus de 2 heures par jour par rapport à des volontaires ayant été exposés au soleil pendant moins de 2 heures par jour. Dans des conditions de faible luminosité, Cutibacterium était plus prévalent dans le bras des personnes jeunes, et Corynebacterium, Anaerococcus et Kytococcus étaient plus prévalents dans le bras des personnes plus âgées. CONCLUSION: La diversité et la composition de la communauté bactérienne sur les joues sont affectées par l'âge et des facteurs extrinsèques (exposition au soleil) peuvent également y jouer un rôle.

Changes in the skin microbiome during male maturation from 0 to 25 years of age.

BACKGROUND: Skin microorganisms co-develop with the human body and age influences the skin microenvironment and thus the skin bacterial community. OBJECTIVES: To investigate the changes in the skin microbiota during male development. METHODS: High-throughput 16S ribosomal RNA pyrosequencing was utilized to analyze the differences in bacterial composition of the skin in healthy males aged 0-25 years. RESULTS: There were significant differences in facial skin bacterial diversity (Shannon index) and richness (Chao index) among the 4 groups of subjects (p < 0.05). Streptococcus, Staphylococcus, Cutibacterium are dominant in males during growth, and regular changes occur with age after birth. Further analysis of skin bacteria between the 4 groups showed that the bacterial abundance of Cutibacterium acnes and Staphylococcus epidermidis tended to increase with age, and the bacterial abundance of Streptococcus, Rothia mucilaginosa, and Staphylococcus hominis tended to decrease with age. CONCLUSIONS: There are some changes in cheek skin bacterial diversity during male development, and there is a relationship between skin bacterial changes and skin development processes.

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.

Interaction of magnolia bark extracts with Staphylococcus aureus DNA and evaluation of the stability of their antibacterial activities.

Magnolia bark is an edible traditional Chinese medicine that has antibacterial activity against Staphylococcus aureus. In the present study, interactions between S. aureus DNA and raw magnolia bark (RMB) and ginger mix-fried magnolia bark (GMB) aqueous extracts were determined via spectroscopic methods. Fluorescence spectroscopy and Stern-Volmer constants showed that S. aureus DNA quenched the fluorescence of the extracts by static quenching. UV-Vis spectroscopy and iodide quenching experiments indicated that the interactions between S. aureus DNA and the fluorescent substances might involve groove binding or electrostatic interactions. In 4', 6-diamidino-2-phenylindole competitive assays, the fluorescence intensity at decreased as the extract amount was increased. This indicates that groove binding is responsible for the fluorescence quenching. The antibacterial activity of GMB aqueous extract treated under light, cold, heat and cycling hot-cold conditions decreased by 13.99, 9.31, 10.89 and 14.40%, respectively, whereas that of RMB aqueous extract treated under the same conditions decreased by 8.91, 14.99, 14.99 and 13.70%, respectively. The results indicate that S. aureus DNA quenches the fluorescence of GMB and RMB aqueous extracts by grooving interactions. Additionally, the antibacterial activities of GMB and RMB extracts are sensitive to light and temperature, respectively.

Cheek Microbial Communities Vary in Young Children with Atopic Dermatitis in China.

BACKGROUND: Atopic dermatitis (AD) is a chronic, recurrent skin condition with recently increased incidence in younger children. AD development has been correlated with the skin microbiome, and Staphylococcus aureus enrichment causes significant increases in skin lesions. OBJECTIVE: Our objectives were to compare the microbial diversity of the cheek skin of children with or without AD aged 0-1 years in China, and to determine whether 4 types of skin-isolated bacteria could inhibit S. aureus in vitro. METHODS: The skin microbial samples of cheek skin of children were sequenced by 16S rRNA V1-V2 region. Four skin isolated bacterial fermentation supernatants were tested for effects on S. aureus growth, membrane formation, and induction of cytokine secretion from HaCaT cells. RESULTS: Bacterial diversity decreased significantly in skin with severe AD compared to healthy skin (p < 0.01). Seven phyla had content >1%, 4 of which differed in AD (p < 0.05). 38 genera had content >1%, 15 differed (p < 0.05). Differences in 8 species were observed (p < 0.05). In vitro antibacterial and cellular experiments showed that S. aureus growth, biofilm formation, and induction of interleukin (IL)-1α and IL-6 secretion from HaCaT cells were significantly inhibited by Klebsiella oxytoca, Kocuria rhizophila, and Staphylococcus epidermidis culture supernatants (p < 0.05). CONCLUSION: Skin microbiome changes in children varied with age and with AD. There were complex interactions between skin isolated bacteria and S. aureus which could inhibit S. aureus growth and biofilm formation in vitro, suggesting that these microorganisms could be used in AD treatment.

Shifts in the skin microbiome associated with diaper dermatitis and emollient treatment amongst infants and toddlers in China.

BACKGROUND: The microbiological basis of diaper dermatitis has not been clearly elucidated; however, a better understanding of microbial colonization may be vital for developing appropriate therapies. METHODS: Using 16S-rRNA gene sequencing technology, we characterized and compared the bacterial communities obtained from the buttock skin sites of children with diaper dermatitis and from healthy controls. Bacterial diversity in the buttock lesion area and subsequent recovery after emollient treatment have been discussed herein. RESULTS: In buttock skin of children with or without diaper dermatitis, Staphylococcus and Anaerococcus were predominant in the total skin microbiome. Compared with the healthy group, the overall skin bacterial richness and diversity were higher in children with diaper dermatitis, with the abundance of Proteobacteria being significantly higher. In the diaper dermatitis group, the richness of Enterococcus, Erwinia and Pseudomonas was significantly higher, and the levels of Clostridium and Actinomyces were significantly lower than those in healthy children. Richness of Staphylococcus aureus was significantly higher in the diaper dermatitis group, whereas that of Staphylococcus epidermidis and Bifidobacterium longum was lower. Staphylococcus epidermidis and Staphylococcus haemolyticus, the dominant species found in buttock skin, were observed to recover earlier after the disease had improved through emollient treatment. CONCLUSION: Staphylococcus epidermidis, as skin probiotic bacterium, and B longum, Clostridium butyricum and Lactobacillus ruminis, which are intestinal probiotic bacteria, are significantly decreased in diaper dermatitis lesions. These changes in the buttock skin microflora indicate an imbalance in the microflora and suggest that the intestinal microflora may be undergoing dynamic changes. The results of this study suggest that probiotic bacterial supplementation may be useful in the treatment and prevention of diaper dermatitis.

Alterations in the skin microbiome are associated with disease severity and treatment in the perioral zone of the skin of infants with atopic dermatitis.

Atopic dermatitis (AD), a chronic relapsing inflammatory pruritic skin disorder with a unique pathophysiology, has a high incidence in the perioral zone among infants. This study aimed to analyze the association of skin microfloral dynamics with disease severity and treatment of AD in 0-1-year-old infants. Based on the eczema area and severity index, subjects were divided into five groups, i.e., mild, moderate, severe, and severe post-treatment, with a healthy control group, and bacterial density at the perioral lesion, disease severity, and treatment were assessed in 0-1-year-old infants with AD. The perioral lesions were colonized predominantly by Firmicutes, followed in abundance by Proteobacteria, Actinobacteria, and Bacteroidetes. In the phylum Firmicutes, Streptococcus was the most predominant genus. In AD infants, the abundance of Bacteroidetes and Fusobacterium decreased significantly with an increase in disease severity (p < 0.01). The abundance of 6 genera, including Prevotella, decreased significantly with an increase in disease severity (p < 0.05). The abundance of Prevotella melaninogenica decreased gradually with an increase in disease severity and increased after treatment; this trend was reversed for Corynebacterium simulans. A reduction in the abundance of Staphylococcus and an increase in that of skin microflora including Prevotella spp., Staphylococcus epidermidis, and Erwinia dispersa were associated with treatment and clinical improvement. Skin bacterial composition varies with AD severity, and Corynebacterium simulans and Prevotella melaninogenica are positively and negatively correlated with AD severity, respectively. This study provides a theoretical basis to identify potential biomarkers AD occurrence and pathogenesis.

A Novel CreA-Mediated Regulation Mechanism of Cellulase Expression in the Thermophilic Fungus Humicola insolens.

The thermophilic fungus Humicola insolens produces cellulolytic enzymes that are of great scientific and commercial interest; however, few reports have focused on its cellulase expression regulation mechanism. In this study, we constructed a creA gene (carbon catabolite repressor gene) disruption mutant strain of H. insolens that exhibited a reduced radial growth rate and stouter hyphae compared to the wild-type (WT) strain. The creA disruption mutant also expressed elevated pNPCase (cellobiohydrolase activities), pNPGase (ß-glucosidase activities), and xylanase levels in non-inducing fermentation with glucose. Unlike other fungi, the H. insolens creA disruption mutant displayed lower FPase (filter paper activity), CMCase (carboxymethyl cellulose activity), pNPCase, and pNPGase activity than observed in the WT strain when fermentation was induced using Avicel, whereas its xylanase activity was higher than that of the parental strain. These results indicate that CreA acts as a crucial regulator of hyphal growth and is part of a unique cellulase expression regulation mechanism in H. insolens. These findings provide a new perspective to improve the understanding of carbon catabolite repression regulation mechanisms in cellulase expression, and enrich the knowledge of metabolism diversity and molecular regulation of carbon metabolism in thermophilic fungi.

Antimicrobial activity and mechanism of Larch bark procyanidins against Staphylococcus aureus.

Larch bark procyanidins (LBPCs) have not only antioxidant and antitumor properties, but also strong bacteriostatic effects. However, it is not clear about the antibacterial mechanisms of LBPC. In this work, the antibacterial effects and mechanisms of LBPC on Staphylococcus aureus were studied in the aspects of morphological structure, cell wall and membrane, essential proteins, and genetic material. The results showed that LBPC effectively inhibited bacterial growth at a minimum inhibitory concentration of 1.75 mg/ml. Bacterial morphology was significantly altered by LBPC treatment, with the cell walls and membranes being destroyed. Extracellular alkaline phosphatase content, bacterial fluid conductivity, and Na+/K+-ATPase and Ca2+-ATPase activities in the membrane system were all increased. In the energy metabolic systems, the activities of succinate dehydrogenase, malate dehydrogenase, and adenosine triphosphatase (ATPase) were all decreased, resulting in a slowdown of metabolism and bacterial growth inhibition. Changes of protein content and composition in the bacteria suggested that the protein expression system was affected. In addition, LBPC was found to bind to DNA grooves to form complexes. Thus, LBPC has a very strong inhibitory effect on S. aureus and can kill S. aureus by destroying the integrity and permeability of the cell wall and cell membrane, affecting protein synthesis, and binding to DNA.

Machine learning assisted rational design of antimicrobial peptides based on human endogenous proteins and their applications for cosmetic preservative system optimization.

Preservatives are essential components in cosmetic products, but their safety issues have attracted widespread attention. There is an urgent need for safe and effective alternatives. Antimicrobial peptides (AMPs) are part of the innate immune system and have potent antimicrobial properties. Using machine learning-assisted rational design, we obtained a novel antibacterial peptide, IK-16-1, with significant antibacterial activity and maintaining safety based on ß-defensins. IK-16-1 has broad-spectrum antimicrobial properties against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans, and has no haemolytic activity. The use of IK-16-1 holds promise in the cosmetics industry, since it can serve as a preservative synergist to reduce the amount of other preservatives in cosmetics. This study verified the feasibility of combining computational design with artificial intelligence prediction to design AMPs, achieving rapid screening and reducing development costs.

A Preliminary Study on the Effectiveness of K-Nearest Neighbor Algorithm Based on Local Mean for Classification of Bioinformatics Data.

The preliminary classification of biological class data is of great importance for bioinformatics. One can quickly classify object data by comparing their existing features with known traits. k-nearest neighbor algorithm is easy to apply in this field, but its drawbacks make it less meaningful to improve the efficiency of the algorithm by simply changing the distance model, so this study uses a local mean-based k-nearest neighbor classifier and compares the accuracy of the predicted classification of six different distance models used. The prediction accuracies in the experimental results were all greater than 70%, and the highest accuracy was achieved in different data sets for all distance models with K=2; the prediction accuracy of Minkowski distance with different parameters had the highest volatility in the test.and the experimental results can be used as a reference for related practitioners.

Synthesis, Stability, and Anti-Tumour Activity of a New Category of "Stapled" Antisense Oligonucleotides with Stimuli-Responsive Feature.

The development of nucleic acid drugs with unique structures and mechanisms has stimulated great research interest. Herein, we report a general strategy to construct "stapled" structures of single-stranded antisense oligonucleotides (ASONs) with a stimuli-responsive feature. "Stapled" cyclic structures can be synthesized with reactive bifunctional handles that react with thiol groups of phosphorothioate (PS)-modified ASONs, and can be alternatively adjusted depending on the desired PS sites in the ASON strand. The disulphide group in the stapled handle can be cleaved in the reducing microenvironment of tumour cells. Thus, "stapled" ASONs may be transformed back to a linear conformation to facilitate binding to target mRNAs. Stapling conferred protection against degradation, and enhanced anti-tumour activity compared to linear counterparts. This study provides a new, effective, and convenient strategy for designing ASONs with "stapled" structures, and also adds a further contribution to facilitate the stability and biological efficacy of novel nucleic acid-based therapeutics.

A novel cyanoacrylate-based matrix excipient in HPMCP capsules forms a sustained intestinal delivery system for orally administered drugs with enhanced absorption efficiency.

Patients prefer oral drug delivery due to its convenience and noninvasiveness. Nevertheless, a multitude of potentially clinically important drugs will not reach the market or achieve their full potential, due to their low bioavailability and instability in gastric acid. In this study, a novel oral drug delivery system based on poly-cyanoacrylate [a polymer of 2-(2-methoxyethoxy)ethyl-2-cyanoacrylate (MECA)] and hydroxypropyl methylcellulose phthalate (HPMCP) was developed and shown to permit intestinal targeting and sustained drug release. Aspirin [acetylsalicylic acid (ASA)] was selected as a model drug for atherosclerosis treatment. It was physically dissolved in liquid MECA, and the ASA-MECA matrix was then polymerized into a solid drug-loading depot in an HPMCP shell. The delivery of the drug depot in the intestine was achieved with the HPMCP shell; then the polymerized MECA (polyMECA) provided sustained drug release. The polyMECA excipient was not absorbed by the intestine due to its high molecular weight; a fluorescein-labeled assay indicated that it was excreted completely in feces after drug release. The formulation, ASA-polyMECA-HPMCP, showed good intestinal targeting and sustained drug release in vitro and in vivo. Pharmacokinetic studies indicated that this formulation improved the bioavailability of ASA relative to commercially available controls. ASA-polyMECA-HPMCP showed desirable anti-atherosclerosis efficacy in a rabbit model, with significant enhancement of atheromatous lesion stability. Biosafety tests proved the low toxicity of ASA-polyMECA-HPMCP and the polyMECA matrix. We believe that this work has provided a practical and biocompatible system for sustained intestinal drug delivery that can be applied broadly with various drugs for specific therapeutic aims.

A review of fatty acids influencing skin condition.

BACKGROUND: Fatty acids are common raw materials in cosmetics and also are an important component of skin surface lipids, and their composition and amount affect the skin condition. AIMS: The purpose of this article was to review the results of basic research on fatty acids as skin surface lipids. METHODS: An extensive literature search was conducted using PubMed, Web of Science, and other databases for articles on fatty acids from 1993 to 2020. RESULTS: This article provides an overview of the mechanisms of fatty acid synthesis and its metabolic pathways as skin surface lipids in the context of sebaceous and intercellular lipids. The three mechanisms by which fatty acids affect the skin condition are also reviewed. CONCLUSIONS: This information will aid further understanding of the mechanism of the fatty acid role in skin function maintenance and provide new perspectives for the management of skin health.

Production of isofloridoside from galactose and glycerol using α-galactosidase from Alicyclobacillus hesperidum.

Isofloridoside (D-isofloridoside and L-isofloridoside) is the main photosynthetic product in red algae. Here, given the importance of isofloridoside, a potentially effective method to produce isofloridoside from galactose and glycerol using whole-cell biocatalysts harboring α-galactosidase was developed. α-Galactosidase-encoding genes from Alicyclobacillus hesperidum, Lactobacillus plantarum, and Bifidobacterium adolescentis were cloned and the proteins were overproduced in Escherichia coli. The α-galactosidase from A. hesperidum (AHGLA) was chosen to synthesize isofloridoside. The effects of reaction pH, temperature, and substrate concentration were investigated. In the optimum biotransformation conditions, the final isofloridoside concentration reached 0.45 M (galactose conversion 23 %). The reaction mixtures were purified using activated charcoal and calcined Celite, and the purified product was identified as a mixture of D- and L-isofloridoside by liquid chromatography-mass spectrometry and nuclear magnetic resonance. This study provides a possible feasible method for the biosynthesis of isofloridoside from low-cost glycerol and galactose.

Skin surface lipidomics revealed the correlation between lipidomic profile and grade in adolescent acne.

BACKGROUND: Acne is a multifactorial skin disorder frequently observed during adolescence with different grades of severity. The crucial factors of acne are the increase of lipids secretion and the change of composition on the skin surface lipid (SSL). However, there are no studies on the changes of lipid composition and content between different grades of adolescent acne in lesional skin and nonlesionsal skin. AIMS: This study was to investigate correlation in the composition of SSL and different grades in order to understand the tendency of SSL alterations in this disease for successful acne management and prevention. METHODS: A powerful analytical technique, UPLC-QTOF-MS, and multivariate data analysis were used to investigate SSL variations of lipid main classes, subclasses, and species. RESULTS: The results indicated that sphinganine, triradylglycerols (TG), and phytosphingosine were important in adolescent acne development. The average fatty acids (FAs) chain length in patients with acne showed significantly shortened trend from mild to moderate adolescent acne. Additionally, the relative average content of TG, diglyceride (DG), FA, ceramides (Cers), and the level of unsaturated FAs significantly increased from mild to moderate adolescent acne. Interestingly, our results demonstrated that the phytosphingosine and sphinganine showed an increasing trend in mild acne groups, but decreasing trend in lesional skin of moderate group. CONCLUSIONS: Lipidomics analysis suggested that the variation of TG, phytosphingosine, and sphinganine was closely related to the occurrence severity of acne in adolescent.

Mechanism and antibacterial activity of vine tea extract and dihydromyricetin against Staphylococcus aureus.

Vine tea (Ampelopsis grossedentata) has been approved as a new food ingredient in 2013. Both vine tea extract (VTE) and its active ingredient, 2R, 3R-Dihydromyricetin (DMY), showed good antibacterial activity. The mechanism of VTE and DMY against Staphylococcus aureus were evaluated by morphology observation, cell membrane and wall assay, protein assay, and DNA assay in this study. The results of SEM and TEM revealed that the VTE and DMY changed the morphology of S. aureus. The leakage of AKPase and ß-galactosidase in treated groups demonstrated that the membrane integrity of S. aureus was disrupted. Meanwhile, the results of protein assay showed that VTE and DMY inhibited the expression of total proteins, and decreased activities of a few energy metabolism enzymes, total ATPase. Moreover, spectral and competitive analysis revealed that VTE and DMY interacted with DNA by groove and intercalation binding. Finally, the suspension experiments of Chinese cabbage and barley showed that inhibitors had strong inhibitory effect on bacteria growth. Overall, the results suggested that VTE and DMY may be potential food preservatives for inhibiting pathogen.

Characterization of antioxidant and antibacterial gelatin films incorporated with Ginkgo biloba extract.

Ginkgo biloba extract (GBE) contains Ginkgo biloba flavonoids, which are phenolic compounds. These compounds can be introduced into films for their functional properties (such as their antioxidant and antibacterial property), allowing this film to be used as food packaging. Thus, the aim of this study was to introduce the GBE into a gelatin solution to prepare gelatin films and evaluate the influence of the natural extract addition on the physicochemical and antimicrobial properties. The gelatin films were successfully prepared by casting technique, and GBE was incorporated at concentrations of 0, 0.5, 1.5, 2.5, 3, 4, and 5 g/100 g of gelatin. The mechanical properties, film solubility, moisture content, water vapor permeability, infrared spectroscopic characteristics, film microstructure, light barrier property, antioxidant property and antibacterial property of the films were investigated. The incorporation of gelatin films with GBE increased the UV-visible shielding performance of films. The antioxidant ability of the film was improved, which was supposed to be related to the active substances of the GBE. The GBE also exhibited potential antimicrobial activity against tested microorganisms. With the increase in the GBE concentration incorporated into the films, the antimicrobial activity of the gelatin film with GBE was also enhanced.

Effect of cosmetic chemical preservatives on resident flora isolated from healthy facial skin.

BACKGROUND/AIMS: Healthy skin harbors numerous microbes known to maintain its health and prevent attacks from external pathogens. The influence of chemical preservatives commonly used in cosmetic products on facial resident flora remains poorly characterized. In this study, we aimed to investigate the antibacterial activity of five such preservatives on in vitro cultivated skin-resident bacteria. METHODS: Both Gram-positive and Gram-negative bacteria were isolated on blood agar, tryptic soy agar, and nutrient agar; Gram-negative bacteria were then selected on Hank's balanced salt solution containing antibiotics and Reasoner's 2A. The minimum inhibitory concentrations (MICs) of methylisothiazolinone (MTI), iodopropynyl butylcarbamate (IPBC), ethylhexylglycerin (EHG), methylparaben (MP), and phenoxyethanol (PE) were estimated for nine facial resident bacteria, Escherichia coli, and Staphylococcus aureus using serial broth dilution in vitro. RESULTS: The maximum test concentrations coincided with the upper limits set by the "Cosmetic Safety and Technical Specification" (2015 edition, China). Nine facial resident bacteria were isolated from 14 healthy adults: Staphylococcus epidermidis, Staphylococcus capitis, Kocuria, Micrococcus luteus, Bacillus, Acinetobacter, Pseudomonas parafulva, Pseudomonas oleovorans, and Roseomonas cervicalis. MTI and IPBC displayed the strongest effect on all tested strains (MICs ≤0.01%), followed by EHG and MP (MICs ≤0.3%), and finally PE with the weakest effect (MIC ≤1%). CONCLUSION: The five chemical preservatives assayed inhibited survival of the nine facial resident bacteria isolates, when tested at the maximum allowed limit. The corresponding MICs will provide a reference for the effective utilization of these compounds in product formulations.

The use of Agrobacterium-mediated insertional mutagenesis sequencing to identify novel genes of Humicola insolens involved in cellulase production.

A transfer DNA (T-DNA)-tagged mutant library of Humicola insolens was screened for mutants with altered cellulase production using the plate-clearing zone assay. Three selected mutants (5-A7, 5-C6, and 13-B7) exhibited significantly depressed FPase, CMCase and xylanase activities compared with the wild-type strain upon shake-flask fermentation, while the pNPCase and pNPGase activities of the three mutants were relatively higher than those of the parental strain. Combined with the results of SDS-PAGE and mass spectrometry, we suggest that expression of the CMCases Cel6B, Cel7B, CMC3, and XynA/B/C was reduced in the mutant strains. Twelve putative T-DNA insertion sites were identified in the three mutants via Agrobacterium-mediated insertional mutagenesis sequencing (AIM-Seq). Bioinformatics analysis suggested that a putative dolichyl pyrophosphate phosphatase, two hypothetical proteins encoding genes of unknown function, and/or nine intergenic fragments may be involved in cellulase and hemicellulase production by H. insolens. This provides promising new candidate genes relevant to cellulase production by the fungus, which will be crucial not only for our understanding of the molecular mechanism underlying cellulase production, but also for strain improvement.