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Category: Genomics and Bioinformatics
Role for Autoinducer-2 in the Development of Commensal Streptococcal Biofilms, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817107/9781555815035_Chap23-1.gif /docserver/preview/fulltext/10.1128/9781555817107/9781555815035_Chap23-2.gifAbstract:
This chapter focuses on the role of the candidate interspecies signaling molecule autoinducer-2 (AI-2), which is produced by the activity of the enzyme LuxS. It discusses its contribution to the development of dental plaque. A number of studies have been conducted on the impact of AI-2 and LuxS on dental plaque development. While investigations of the role(s) of AI-2 are still in their infancy, it is clear that the activity of LuxS and AI-2 moderates certain phenotypic characteristics of oral commensal and oral pathogenic bacteria. Particular notice in this chapter is given to LuxS-and AI-2-mediated interactions between the commensals Streptococcus oralis 34 and Actinomyces oris T14V, which are two initial colonizers of dental plaque. LsrB-like ribose transport periplasmic binding protein, in concert with LsrB, enhances biofilm formation through the recognition and uptake of AI-2. Of relevance to the oral streptococci and this chapter, a cursory examination of streptococcal genomes indicates that various Streptococcus spp. express RbsB-like protein. Thus, membrane-bound receptors and/or transport proteins may facilitate accumulation of AI-2 and intracellular signaling in streptococci. This chapter discusses studies of S. oralis 34 and A. oris T14V and their implication in future studies of AI-2-mediated communication. An interesting aspect of Sorbarod studies was that the data suggested that colocalization of S. oralis 34 and A. oris T14V facilitates the uptake and/or sequestering of AI-2 by one or both species.
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Diagram showing the biochemical pathway by which oral streptococci produce AI-2. DPD is produced as a consequence of the activity of the activated methyl cycle within the streptococcal cell (shown on the right). DPD spontaneously forms a collection of inter-convertible molecules in equilibrium. These are DPD-hydrate, R-THMF, S-THMF, and S- THMF-borate, as well as other possible borated forms. R-THMF is recognized by S. enterica serovar Typhimurium, and S-THMF-borate is recognized by V. harveyi. Molecules described for the activated methyl cycle include SAM synthetase (MetK), SAM, SAH, adenosylhomocysteine nucleosidase (Pfs), SRH, S-ribosylhomocysteinase (LuxS), cobalamin-independent methionine synthase (MetE), cobalamin-dependent methionine synthase (MetH), 5-methyltetrahydrofolate (H3C-THF), 5-methyltetrahydropteroryl glutamate (H3C-THPG), tetrahydrofolate (THF), and tetrahydropteroryl glutamate (THPG).