Analysis of the influence of host lifestyle (coffee consumption, drinking, and smoking) on Korean oral microbiome.

If a DNA sample collected in the field is old or degraded, short tandem repeat analysis is difficult to perform, a representative analysis method currently used for individual identification. Given that microorganisms exist everywhere and within the human body, in similar amounts to human cells, microbial analysis could be used to identify individuals even in cases in which human DNA-based identification is difficult. Research has demonstrated that the types of microorganisms within the human body differ depending on various internal or external factors, such as body part or bodily fluid type, lifestyle, geographical area of residence, sex, and age. In this study, we aimed to examine the relationship between lifestyle factors and the composition and diversity of the oral microbiome in individuals living in Korea. We collected 43 saliva samples from Korean individuals and analyzed the oral microbiome and its variations due to external factors, such as coffee consumption, drinking, and smoking. Linear discriminant analysis effect size revealed that Oribacterium, Campylobacter, and Megasphaera were abundant in coffee consumers, whereas Saccharimonadales, Clostridia, and Catonella were abundant in alcohol non-drinkers. We found increased levels of Stomatobaculum in the saliva of smokers, compared with that of non-smokers. Thus, our analysis revealed characteristic microorganisms for each parameter that was evaluated (coffee consumption, smoking, drinking). Consequently, our study provides insight into the oral microbiome in the Korean population and lays the foundation for developing the Korean Forensic Microbiome Database.

Optimization of DNA extraction and sampling methods for successful forensic microbiome analyses of the skin and saliva.

Microbiome studies have contributed to many fields, such as healthcare and medicine; however, these studies are relatively limited in forensics. Microbiome analyses can provide information, such as geolocation and ancestry information, when short tandem repeat (STR) profiling fails. In this study, methods for DNA extraction and sampling from the skin and saliva were optimized for the construction of a Korean Forensic Microbiome Database (KFMD). DNA yields were estimated using four DNA extraction kits, including two automated kits (Maxwell® FSC DNA IQ™ Casework Kit and PrepFiler™ Forensic DNA Extraction Kit, updated) and two manual kits (QIAamp DNA Mini Kit and QIAamp DNA Micro Kit) commonly used in forensic DNA profiling laboratories. Next-generation sequencing of the 16S rRNA V4 region was performed to analyze microbial communities in samples. The Bacterial Transport Swab with Liquid Media (NobleBio), two cotton swabs (PoongSung and Puritan), and nylon-flocked swabs (NobleBio and COPAN) were tested for DNA recovery. The PrepFiler and Maxwell kits showed the highest yields of 3.884 ng/µL and 23.767 ng/µL from the scalp and saliva, respectively. With respect to DNA recovery, nylon-flocked swabs performed better than cotton swabs. The relative abundances of taxa sorted by DNA extraction kits were similar contributions; however, with significant differences in community composition between scalp and saliva samples. Lawsonella and Veillonella were the most abundant genera in the two sample types. Thus, the Maxwell® FSC DNA IQ™ Casework Kit and nylon-flocked swab (NobleBio) were optimal for DNA extraction and collection in microbiome analyses.