| dc.description.abstract | Biofilms are highly organized bacterial structures that are attached to a surface.
They are ubiquitous in nature and may be detrimental, causing numerous types of
illnesses in living organisms. Biofilms in the human oral cavity are the main cause of
dental caries and periodontal diseases and can act as a source for pathogenic organisms
to spread within the body and cause various types of systemic diseases. Streptococcus
mutans is the primary etiological agent of dental caries, the single most chronic
childhood disease. In many cases, quorum sensing (QS) is required for initial formation
and subsequent development of biofilms and the signaling molecule autoinducer 2 (AI-
2) has been well studied as an inter-species QS signaling molecule. However, recent
reports also suggest that AI-2-mediated signaling is important for intra-species biofilm
formation in both Gram-negative and positive bacteria. Therefore, there is significant
interest in understanding the role of different QS signals such as AI-2 in oral biofilm
formation. Microfluidic devices provide biomimetic environments and offer a simple
method for executing multiple stimuli experiments simultaneously, thus, can be an
extremely powerful tool in the study of QS in biofilms. In this study, we report conditions that support the development of S. mutans
biofilms in microchannel microfluidic devices, and the effects of extracellular addition
of chemically synthesized (S)-4,5-dihydroxy-2,3-pentanedione (DPD; precursor of AI-2)
on mono-species S. mutans luxS (AI-2 deficient strain) biofilm formation using a
gradient generating microfluidic device. S. mutans wild type (WT) and luxS biofilms
were developed in nutrient rich medium (25% brain heart infusion medium, BHI + 1%
sucrose) for up to 48 h. Maximum biofilm formation with both strains was observed
after 24 h, with distinct structure and organization. No changes in S. mutans luxS
biofilm growth or structure were observed upon exposure to different concentrations of
AI-2 in a gradient generating device (0 to 5 M). These results were also validated by
using a standard 96-well plate assay and by verifying the uptake of AI-2 by S. mutans
luxS. Our data suggest that extracellular addition of AI-2 does not complement the luxS
deletion in S. mutans with respect to biofilm formation. | en |
