However, to our knowledge, our work represents the first in vivo analysis in which this association has been demonstrated and the behavioral consequences have been analyzed in a complete organism, and, interestingly, our results suggest significant evolutionary conservation. Moreover, we have demonstrated that Ih current regulates dopamine circadian and light-dependent oscillations, and provided evidences indicating that cyclic dopamine signaling is essential for normal behavior. Therefore, our data should be considered not only in view of the value of HCN channels as therapeutic targets, but also when approaching functional and pathological studies of dopamine-related processes. In this sense, our data corroborate the usefulness of Drosophila as a model for these types of studies. Autoinducers play important roles as quorum-sensing signals in bacterial cell-cell communication. Through the accumulation of bacterially produced signaling molecules the bacterial population is able to sense increases in cell density and alter gene expression accordingly. This allows coordinated expression of genes at the population level involved in behaviors, which are most effective at higher cell densities, such as pathogenicity, biofilm Dasatinib formation, production of extracellular proteins and others. For an excellent review on interspecies signaling, we refer to Shank and Kolter. Many quorum sensing mechanisms in Gram-negative bacteria involve N-AHLs, signal molecules whose general mechanism of synthesis is well understood. By now, about 20 proteins belonging to 10 different clusters have been found interfering with these bacterial quorum sensing molecules. Most of these enzymes belong to the enzyme class of hydrolases. Mainly two types of hydrolases act on autoinducer I molecules: The majority of the Vismodegib identified enzymes are lactonases and this group of enzymes has been reviewed recently. More recently three additional lactonases have been published. Lactonases hydrolyze the lactone ring in a reversible way. Furthermore acylases are known to interfere with the autoinducer I-like molecules. Aminoacylases cleave the lacton ring off the fatty acids. Acylases have been identified in a variety of microorganisms: Comamonas sp., P. aeruginosa, P. syringae, Ochrobactrum sp., Ralstonia sp., Rhodococcus erythropolis, Shewanella sp. and Streptomyces sp.. Surprisingly, only very few oxidoreductases have been found to influence quorum sensing controlled phenotypes. Up to date only one, a P-450/NADPH-P450 monooxygenase has been isolated from Bacillus megaterium and characterized in detail. The respective AHL oxidizing enzyme was designated CYP102A1 and it was able to oxidize both long chained AHLs and fatty acids with varying chain length at various positions.