Journal List > J Korean Acad Oral Health > v.41(1) > 1057741

Kim, Woo, Lee, Kim, Lee, and Jeong: Red fluorescence of oral bacteria interacting with Porphyromonas gingivalis



Dental plaque is composed of 700 bacterial species. It is known that some oral microorganisms produce porphyrin, and thus, they emit red fluorescence when illuminated with blue light at a specific wavelength of <410 nm. Porphyromonas gingivalis belongs to the genus Porphyromonas, which is characterized by the production of porphyrin. The aim of this study was to evaluate red fluorescence emission of some oral microorganisms interacting with P. gingivalis.


Five bacterial strains (P. gingivalis, Streptococcus mutans, Lactobacillus casei, Actinomyces naeslundii, and Fusobacterium nucleatum) were used for this study. Tryptic soy agar medium supplemented with hemin, vitamin K3, and sheep blood was used as a growth medium. The fluorescence emission of bacterial colonies was evaluated under 405 nm-wavelength blue light using a Quantitative Light-induced Fluorescence Digital (QLF-D) camera system. Each bacterium was cultured alone and co-cultured in close proximity with P. gingivalis. The red/green (R/G) ratio of fluorescence image was calculated and the differences of R/G ratio according to each growth condition were compared using the Mann-Whitney test (P<0.05).


Single cultured S. mutans, L. casei and A. naeslundii colonies emitted red fluorescence (R/G ratio=2.15±0.06, 4.31±0.17, 5.52±1.29, respectively). Fusobacterium nucleatum colonies emitted green fluorescence (R/G ratio=1.36±0.06). The R/G ratios of A. naeslundii and F. nucleatum were increased when P. gingivalis was co-cultured with each bacterium (P<0.05). In contrast, the R/G ratios of S. mutans and L. casei were decreased when P. gingivalis was co-cultured with each bacterium (P=0.002, 0.003).


This study confirmed that P. gingivalis could affect the red fluorescence of other oral bacteria under 405 nm-wavelength blue light. Our findings concluded that P. gingivalis has an important role for red fluorescence emission of dental biofilm.

Figures and Tables

Fig. 1

The blue-light image of S. mutans, L. casei, A. naeslundii, F. nucleatum cultivated on TSA blood media. Fluorescence images of left side were cultivated single at each plate, right side were cultivated in close proximity with P. gingivalis.

Table 1

Bacterial strains and culture requirement

Table 2

Red fluorescence assessment of oral bacteria grown in single- and co-culture


*: mean R/G vlaue with standard deviation.

+: The emission of red fluorescence was detected.

−: The emission of red fluorescence was not detected.


This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2014R1A1A1005924).


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