Online Journal of Biological Sciences 6 (2): 62-66, 2006 ISSN 1608-4217 © 2006 Science Publications Corresponding Author: Prof. Dr. Zubaidah Hj Abdul Rahim, Department of Oral Biology, Faculty of Dentistry, University of Malaya, 50603 Kuala Lumpur, Malaysia, Tel/Fax: 603-79674851/603-79674536 62 The Role of Sucrose in the Development of Oral Biofilm in a Simulated Mouth System Wan Nordini Hasnor Wan Ismail, Fathilah Abdul Razak and Zubaidah Hj Abdul Rahim Department of Oral Biology, Faculty of Dentistry, University of Malaya 50603 KUALA Lumpur, Malaysia Abstract: The development of oral biofilm consisting of early settlers and late settlers in the presence and absence of sucrose using a simulated mouth model was investigated. The experiments were carried out by growing the early settlers’ biofilm consisting of Strep. mitis and Strep. sanguinis and late settlers’ biofilm of Strep. mutans in the simulated mouth system. Experiments using three different nutrient conditions (A, B and C) were carried out. In A, sterile saliva was used as the nutrient source in which the early settlers were suspended and pumped into the simulated mouth system and allowed to grow for 24 hrs. In B, 1% of BHI broth was added to the sterile saliva three times a day at 6 hrs interval to demonstrate the effect of glucose on the development of the biofilms. In C, the 1% BHI was supplemented with 1% sucrose in order to show the effect of glucose in the presence of sucrose on the development of the biofilm. The experiments were subsequently repeated with the late settlers. In all the experiments, A serves as the control where the nutrient source is minimal. The data collected were analyzed using Student t-test. From the results obtained, it was observed that both glucose and sucrose enhanced the development of early and late settlers’ biofilms. The growth of late settlers’ biofilm however, was found to be significantly higher in the presence of sucrose (93x10 6 CFU mL 1 ) compared to glucose (66x10 6 CFU mL 1 ) with a p value <0.05. Key words: Early settlers’ biofilm, late settlers’ biofilm, simulated mouth system INTRODUCTION Sucrose yields one equivalent of glucose and one equivalent of fructose upon hydrolysis. In industrialized societies, sucrose is commonly used as sweetening agent and it had been reported that consumption of sucrose is about 50 kg per person per year [1] . Sucrose has been considered to be associated with dental caries. Sucrose can be utilized by extracellular bacterial enzymes for the formation of extracellular polysaccharides (glucans and fructans) in dental plaque [1-4] . The formation of glucan is catalyzed by glucosyltransferase (GTF) and fructan by fructosyltransferase (FTF) [5-7] . Glucan plays a role in plaque formation as well as facilitates the bacterial attachment to the tooth surface [8-10] . Fructan contributes to the virulence of the biofilm by acting as binding sites for the adhesion of Strep. mutans [7] . Sucrose consumption can result in a decrease in pH in both non- starved and starved biofilms of Strep. mutans [11] . The early development of oral biofilm (dental plaque) exhibits colonies of Streptococcus sanguinis and Streptococcus mitis [5,12] . Both streptococci belong to mitis-group [1,13] . Strep. sanguinis is capable of producing water-insoluble mutans and water-soluble dextran from sucrose [1] whereas Strep. mitis may produce water-soluble dextran [14] . In the oral cavity, these microbes usually exist as biofilm on the tooth surfaces and surrounded by protective matrix made up of extracellular polymers [1] . Strep. mutans on the other hand, belongs to mutans-group and has been associated with dental caries [13] . Dietary sucrose is essential for the accumulation of this group on teeth and initiation of carious lesions on smooth enamel surfaces [15] . Strep. mutans synthesized extracellular polysaccharide from sucrose by the action of two enzymes, GTF and FTF. When the bacteria are grown in the presence of any carbohydrate, addition of sterile sucrose to the culture results in the formation of extracellular polymers [16] . Strep. mutans produces three types of GTF that convert sucrose into glucans; (i) GTF synthesize water-soluble glucan, (ii) GTF synthesize water-insoluble glucan and (iii) GTF synthesize both types of glucan [10,17] . The close relationship between sucrose, Strep. mutans and caries development had been well documented for centuries [2,18-21] . However, little or no information has been discussed on the role of carbohydrate in the formation of early settlers’ biofilm. In this study, the role of glucose and sucrose on the growth of the oral biofilm consisting of early settlers (Strep. mitis and Strep. sanguinis) was investigated using a simulated mouth model and compared with that of the late settlers.