|Year : 2016 | Volume
| Issue : 1 | Page : 12-14
Real-time monitoring of cariogenic bacteria via bioluminescent imaging: A biodontic hypothesis
Independent Research Scientist, Founder and Managing Editor of Dental Hypotheses, Isfahan, Iran
|Date of Web Publication||24-Feb-2016|
No. 24, Faree 15, Pardis, Shahin Shahr, Isfahan - 83179 18981
Source of Support: None, Conflict of Interest: None
Introduction: Dental caries (tooth decay) remains one of the most common chronic infectious disease in the world. Disclosure of camouflaged cariogenic bacteria will be a great motivation for better oral hygiene. The Hypothesis: At present, lux transposon cassette, Tn4001 luxABCDE Kmr, is available that could be used for stable bioluminescent transformation of a wide range of gram-positive bacteria, e.g. Streptococcus mutans and Lactobacillus. After this step, sensitive charge-coupled device (CCD) camera could be used to detect the low levels of light emitted from bioluminescent cariogenic bacteria. Living imaging software would be used for analysis and three-dimensional (3D) reconstruction of images. Evaluation of the Hypothesis: Entrance of transgenic organisms into the oral cavity should be done with great caution. Ethical consideration is necessary and primary animal studies are required. The main limitation of this technique will be oxygen. As mentioned previously, bioluminescent reactions need oxygen. Hence, bioluminescent imaging cannot be used for anaerobic bacteria, e.g., Streptococcus sobrinus.
Keywords: Biodontics, bioluminescent imaging, dental caries, Streptococcus mutans, Lactobacillus
|How to cite this article:|
Kolahi J. Real-time monitoring of cariogenic bacteria via bioluminescent imaging: A biodontic hypothesis. Dent Hypotheses 2016;7:12-4
| Introduction|| |
Dental caries (tooth decay) remains one of the most common chronic infectious diseases in the world. It is widely believed that some species of bacteria, e.g., Streptococcus mutans and Lactobacillus have a major role in the etiology of dental caries. These facultative anaerobic, gram-positive microorganisms can produce high levels of lactic acid via the fermentation of dietary sugars.
What is bioluminescence?
Bioluminescence is the creation and emission of light by organisms that are alive, e.g., bioluminescent bacteria, fungi, and terrestrial invertebrates such as fireflies. Bioluminescence is a form of chemiluminescence where light energy is produced by a chemical reaction between light-emitting pigment, luciferin, and oxygen, which is catalyzed by the lucifrase enzyme [Figure 1]. 
|Figure 1: Schematic diagram of bioluminescent reaction. For this reaction, ATP is required and consequently, CO2, AMP, and phosphate groups are released as waste products. The reaction will be catalyzed by cofactors such as Ca2+ or Mg2+ ions|
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Fungi and bacteria have a tendency to emit continuous light. In contrast, algae and animal species produce light that flashes. Most of the bioluminescent organisms produce blue and green light.  However, there are species that radiate red and infrared light, and one genus has been found to emit yellow bioluminescence. Bioluminescence has five purposes that have been known to date: camouflage, attraction, repulsion, communication, and illumination. 
Uses of bioluminescence in biotechnology and medicine
Utilization of bioluminescence is very interesting, yet it is not a new idea. Bottles containing fireflies had been used at mines as a weak source of light to avoid using candles, which risked sparking explosions of firedamp.  The pioneer attempt to create transgenic organism was reported as early as 1986 when firefly luciferase gene was transferred to tobacco plants.  At present, glowing plants are commercially available,  and glowing trees could light up city streets.  Of more interest, in June 2013 at Kickstarter, a crowdfunding site, an exciting project was started about Glowing Plants. 
However, in medicine bioluminescence phenomena were used widely in reporter genes.  Another interesting and emerging field is bioluminescence imaging, which could be used for in vivo studies of infection (with bioluminescent pathogens), cancer progression (using a bioluminescent cancer cell line), and reconstitution kinetics (using bioluminescent stem cells). 
| The Hypothesis|| |
Bioluminescence imaging opens up new perspectives for research scientists to identify new aspects of host-pathogen interactions.  At bioluminescent bacteria such as Photorhabdus luminescens or Xenorhabdus luminescens, the lux operon encodes genes to synthesize luciferase and the substrate luciferin [Figure 1]. Bacterial lux operon luciferase has peak emissions at 490 nm (blue-green). At present, lux transposon cassette, Tn4001 luxABCDE Kmr, is available that could be used for stable bioluminescent transformation of a wide range of gram-positive bacteria.  The main cariogenic bacteria e.g. Streptococcus mutans and Lactobacillus are gram-positive and could be genetically engineered for real-time bioluminescent imaging. Recombinant bioluminescent cariogenic bacteria could be transferred to the oral cavity. After this step, sensitive charge-coupled device (CCD) camera could be used to detect the low levels of light emitted from bioluminescent cariogenic bacteria. Living imaging software would be used for analysis and 3D reconstruction of images [Figure 2]. [12
|Figure 2: Theoretical example of a bioluminescent smile showing transgenic cariogenic bacterial in the oral cavity|
Click here to view
Nevertheless, to distinguish between different carcinogens multicolor strategy would be useful. For this technique different bioluminescent systems could be used. Firefly (Photinus pyralis) luciferase (green to yellow region, typically 550-570 nm) and click beetle (Pyrophorus plagiophthalamus) luciferase (red light of 611 nm) would be good candidates.  In contrast to bacterial lux operon luciferase, this eukaryotic bioluminescent systems need exogenous luciferin substrate to emit light. 
| Evaluation of The Hypothesis|| |
Disclosure of camouflaged cariogenic bacteria will be a great motivation for better oral hygiene. Yet, entrance of transgenic organisms into the oral cavity should be done with great caution. Ethical consideration is necessary and primary animal studies are required. Unbelievably, I have heard about commercial bioluminescent candy, toothpaste, etc. 
However, the main limitation of this technique will be oxygen. As mentioned previously, bioluminescent reactions need oxygen [Figure 1]. Hence, bioluminescent imaging cannot be used for anaerobic bacteria, e.g., Streptococcus sobrinus.
I would like to express my deep gratitude and appreciation to Professor Edward F. Rossomando, father of biodontics dentistry.  This hypothesis is a continuation of the primary researches (1999) at Biotechnology Research Group of Student Research Center, Isfahan University of Medical Sciences, Isfahan, Isfahan Province, Iran. I would like to thank www.photofunny.net for allowing me to generate a theoretical example of a bioluminescent smile.
Financial support and sponsorship
Conflicts of interest
Author has editorial involvement with Dent Hypotheses.
| References|| |
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[Figure 1], [Figure 2]