Shmuel Carmeli

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Acinetobacter radioresistens KA53, isolated by enrichment culture, was found to produce an extracellular, nondialyzable emulsifying agent (referred to as alasan) when grown on ethanol medium in a batch-fed reactor. The crude emulsifier was concentrated from the cell-free culture fluid by ammonium sulfate precipitation to yield 2.2 g of emulsifier per liter.(More)
mazEF is a toxin-antitoxin module located on many bacterial chromosomes, including those of pathogens. Here, we report that Escherichia coli mazEF-mediated cell death is a population phenomenon requiring a quorum-sensing molecule that we call the extracellular death factor (EDF). Structural analysis revealed that EDF is a linear pentapeptide,(More)
Microcystins constitute a serious threat to the quality of drinking water worldwide. These protein phosphatase inhibitors are formed by various cyanobacterial species, including Microcystis sp. Microcystins are produced by a complex microcystin synthetase, composed of peptide synthetases and polyketide synthases, encoded by the mcyA-J gene cluster. Recent(More)
Effects of two cyanobacterial compounds, microcin SF608 and microcystin-LR, were investigated on different physiological parameters of two organisms, the water moss, Vesicularia dubyana, and the waterflea, Daphnia magna. Both compounds are produced by Microcystis species. Microcystin-LR is a potent inhibitor of protein phosphatases 1 and 2A, and microcin(More)
Five novel diacylated sulfoglycolipids (1-5) were isolated from the cyanobacterium Scytonema sp. (TAU strain SL-30-1-4) and four novel acylated diglycolipids (6-9) were isolated from the cyanobacterium Oscillatoria raoi (TAU strain IL-76-1-2). These two groups of glycolipids and related known glycolipids isolated from these two and three other strains of(More)
Four modified cyclic hexapeptides, tenuecyclamides A-D (1-4), were isolated along with the known antibiotic, borophycin (5), from the methanol extract of Nostoc spongiaeforme var. tenue (TAU strain IL-184-6). The planar structure of tenuecyclamides A-D (1-4) was determined by homonuclear and inverse-heteronuclear 2D-NMR techniques as well as by(More)
A new natural derivative of the sulfated guanidinium zwitterionic toxin cylindrospermopsin, 7-epi-cylindrospermopsin, was recently isolated from the cyanobacterium Aphanizomenon ovalisporum (Forti). The toxicity of the molecule (LD50 ip 5 d), estimated by mouse bioassay, was 200 microg/kg mouse, a value similar to that of cylindrospermopsin. Treatment of(More)
Bioassay-guided fractionation of the 7:3 MeOH/water extract of a cultured cyanobacterium strain identified as Fischerella sp. yielded nine isonitrile-containing alkaloids. Three of the compounds, ambiguine H isonitrile (1), ambiguine I isonitrile (2), and ambiguine J isonitrile (3), are new, while the other six, 12-epi-hapalindole H, ambiguine A isonitrile,(More)
Three novel meroterpenoids, insuetolides A-C (1-3) and four drimane sesquiterpenes, the new (E)-6-(4'-hydroxy-2'-butenoyl)-strobilactone A (4) and the known 2α, 9α, 11-trihydroxy-6-oxodrim-7-ene (5), strobilactone A (6) and (E,E)-6-(6',7'-dihydroxy-2',4'-octadienoyl)-strobilactone A (7), were isolated from the EtOAc extract of the culture medium of the(More)
Tolytoxin, a macrocyclic lactone, is a potent antifungal antibiotic, exhibiting MICs in the range of 0.25 to 8 nanomolar. Tolytoxin also inhibits the growth of a variety of mammalian cells at similar doses, without specific inhibition of macromolecular synthesis. The effects in mammalian cells are primarily cytostatic, with cell death being time-and(More)