Vibrio vulnificus was found to produce a chemical that induced the expression of Vibrio fischeri lux genes. Electron spray ionization-mass spectrometry and 1 H nuclear magnetic resonance analyses indicated that the compound was cyclo(L-Phe-L-Pro) (cFP). The compound was produced at a maximal level when cell cultures reached the onset of stationary phase. Sodium dodecyl sulfate-polyacrylamide gel analysis of the total proteins of V. vulnificus indicated that expression of OmpU was enhanced by exogenously added synthetic or purified cFP. A toxR-null mutant failed to express ompU despite the addition of cFP. The related Vibrio spp. V. cholerae, V. parahaemolyticus, and V. harveyi also produced cFP, which induced the expression of their own ompU genes. cFP also enhanced the expression in V. cholerae of the ctx genes, which are known to be regulated by ToxR. Our results suggest that cFP is a signal molecule controlling the expression of genes important for the pathogenicity of Vibrio spp.Communication between cells via diffusible chemicals is a general phenomenon found in virtually all living organisms. However, it is only in the last 2 decades that it has been intensively studied in bacteria. One of the best-known examples is quorum sensing. A number of bacteria associated with eukaryotic hosts employ quorum-sensing systems to sense their population density, thereby modulating the expression of sets of genes involved in physiological responses associated with survival, propagation, and/or virulence (9,21,44). N-Acylhomoserine lactones (AHLs) are the most prevalent signal molecules for quorum sensing in gram-negative bacteria, but not all signal molecules belong to this group. For instance, Vibrio harveyi employs a furanosyl borate diester molecule in addition to AHL (7). The plant pathogen Ralstonia solanacearum uses 3-hydroxypalmitic acid methyl ester together with AHL to control the expression of virulence factors (14), and several gram-positive bacteria utilize peptides or ␥-butyrolactone as signals (for a review, see reference 12). Xanthomonas campestris also uses non-AHL signal molecules, which have been identified as fatty acid derivatives, to regulate the expression of virulence factors (3, 54). In addition, cyclic dipeptides produced by Pseudomonas spp. and some other genera can activate AHL bioindicator strains (22). They probably activate or antagonize signaling components implicated in AHL-dependent quorum sensing by cross talk with the associated sensors. However, the actual biological roles of these cyclic dipeptide molecules remain to be clarified.Vibrio vulnificus is an opportunistic human pathogen that causes severe wound infection and primary septicemia (50). It has been reported to possess a functional luxS and produce a signal molecule that induces bioluminescence in a V. harveyi AI-2 reporter strain (25). It is also known to possess smcR, a homolog of the positive regulatory gene luxR of V. harveyi (29). SmcR induces the expression of vvpE, encoding a metalloprotease, and represses vvhAB, encodin...
Various enantiomerically pure 2-acylaziridines were prepared efficiently from the corresponding aziridine-2-carboxylate via Weinreb's amide and the subsequent treatment of organometallic compounds. The carbonyl group of those 2-acylaziridines was stereoselectively reduced by NaBH4in the presence of ZnCl2 to give erythro-1,2-amino alcohols with high diastereoselectivities and chemical yields. Using this methodology, we prepared (1R,2S)-N-Boc-norephedrine 5, N-Boc-safingol 8, N-Boc-D-erythro-sphinganine 9, and N-Boc-spisulosine 10 in high yields.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.