R.J. Palmer Jr.
David S. Blehert
S.R. Campagna
M.F. Semmelhack
P.G. Egland
B.L. Bassler
P.E. Kolenbrander
A.H. Rickard
2006
<p><span>4,5-dihydroxy-2,3-pentanedione (DPD), a product of the LuxS enzyme in the catabolism of </span><i>S</i><span>-ribosylhomocysteine, spontaneously cyclizes to form autoinducer 2 (AI-2). AI-2 is proposed to be a universal signal molecule mediating interspecies communication among bacteria. We show that mutualistic and abundant biofilm growth in flowing saliva of two human oral commensal bacteria, </span><i>Actinomyces naeslundii</i><span> T14V and </span><i>Streptococcus oralis</i><span> 34, is dependent upon production of AI-2 by </span><i>S. oralis</i><span> 34. A </span><i>luxS</i><span> mutant of </span><i>S. oralis 34</i><span> was constructed which did not produce AI-2. Unlike wild-type dual-species biofilms, </span><i>A. naeslundii</i><span> T14V and an </span><i>S. oralis</i><span> 34 </span><i>luxS</i><span> mutant did not exhibit mutualism and generated only sparse biofilms which contained a 10-fold lower biomass of each species. Restoration of AI-2 levels by genetic or chemical (synthetic AI-2 in the form of DPD) complementation re-established the mutualistic growth and high biomass characteristic for the wild-type dual-species biofilm. Furthermore, an optimal concentration of DPD was determined, above and below which biofilm formation was suppressed. The optimal concentration was 100-fold lower than the detection limit of the currently accepted AI-2 assay. Thus, AI-2 acts as an interspecies signal and its concentration is critical for mutualism between two species of oral bacteria grown under conditions that are representative of the human oral cavity.</span></p>
application/pdf
10.1111/j.1365-2958.2006.05202.x
en
Wiley
Autoinducer 2: a concentration-dependent signal for mutualistic bacterial biofilm growth
article