Temporal dynamics of bacterial microbiota in the human oral cavity determined using an in situ model of dental biofilms

• Published in: NPJ biofilms and microbiomes Vol. 2; no. 1; p. 16018
• Main Authors: Wake, Nanako, Asahi, Yoko, Noiri, Yuichiro, Hayashi, Mikako, Motooka, Daisuke, Nakamura, Shota, Gotoh, Kazuyoshi, Miura, Jiro, Machi, Hiroyuki, Iida, Tetsuya, Ebisu, Shigeyuki
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.08.2016; Nature Publishing Group
• Subjects: 631/326/46; 692/700; Biomedical and Life Sciences; Life Sciences; Medical Microbiology; Microbial Ecology; Microbial Genetics and Genomics; Microbiology
• ISSN: 2055-5008; 2055-5008
• DOI: 10.1038/npjbiofilms.2016.18

Numerous studies on oral biofilms have been performed in vitro , although it is difficult to mimic the oral environment. Here we used an in situ model to conduct a quantitative analysis and comprehensive identification of bacterial communities over time by performing deep sequencing of 16S rRNA genes. We show here that the number of viable bacteria in supragingival biofilms increased in two steps. Using scanning and transmission electron microscopy, as well as confocal laser scanning microscopy, we detected gram-positive cocci during the first 8 h. The biofilm was subsequently covered with a thick matrix-like structure composed of different bacterial morphotypes that diversified as the number of bacteria increased. Streptococcus accounted for >20% of the population until 16 h, and obligate anaerobes such as Fusobacterium, Prevotella and Porphyromonas predominated after 48 h, and this increase was statistically significant after 96 h ( P <0.05). Together, our data demonstrate that an initial population of facultative anaerobic bacteria was replaced with a population of gram-negative anaerobic bacteria during oral biofilm formation. This study, therefore, contributes to a comprehensive understanding of the composition of the bacterial microbiota involved in the health of the human oral cavity. Dentistry: Composition of human oral bacteria changes with time A novel technique allows direct monitoring of time-dependent changes in the communities of bacteria that inhabit the human mouth. Headed by Nanako Wake and Yoko Asahi of Osaka University Graduate School of Dentistry, a team in Japan inserted acrylic splints into the mouths of healthy volunteers. The nature of bacterial growth on the splints was then subjected to regular quantitative analysis and comprehensive identification over a 4-day period. The authors found that the initial population of facultative anaerobic bacteria (which can respire both with and without oxygen) became replaced by one of obligate anaerobic bacteria (which die in the presence of oxygen). The results of this study shed light on our understanding of the dynamics of human oral bacterial populations and the origins of caries and gum disease.