Social Class

Discussion of class structure in fifth-century Athens, historical constitution of theater audiences, and the changes in the comic representation of class antagonism from Aristophanes to Menander

New antibiotics from a marine isolate of Bacillus laterosporus

The continued chemical investigation of a marine isolate of Bacillus laterosporus has resulted in the discovery of nine new metabolites, seven of which displayed antibiotic activity. The bogorols A - E (26-30) were found to comprise a novel structural template of the cationic peptide class of antibiotics, while the basiliskamides A and B (50 and 51) were discovered to possess potent antifungal activity versus both Candida albicans and Aspergillus fumigatus. Two structurally novel acyldipeptides, tupuseleiamides A and B (55 and 56), were the result of a serendipitous discovery. The structures in this thesis were elucidated using a combination of NMR spectroscopy, mass spectrometry, and chemical degradation coupled with chiral GC analyses. The fragmentation pattern observed in the mass spectrum of 26 allowed for the rapid structure elucidation of 27-30. An empirical method based on steric and electronic arguments was used in conjunction with a series of partial acid hydrolyses to rationalize the relative placement of the enantiomeric pairs of amino acids within the constitution of 26. A series of common structural features defined the novel bogorol cationic peptide template. The C and N termini of the linear peptides were found to be capped by an amino alcohol and an α-hydroxy acid, respectively, leaving the cationic residues to reside solely in the interior of the peptide. In addition, the bogorols contained the uncommon amino acid, E-2-amino-2-butenoic acid. A preliminary investigation of the secondary structure of the bogorols revealed their propensity to exist as ahelices, thus allowing 26-30 to adopt the amphipathic structure characteristic of cationic peptide antibiotics. The bogorols were found to exhibit in vitro antimicrobial activity versus methicillin resistant Staphylococcus aureus and vancomycin resistant Enterococcus spp. comparable to that found with other cationic peptide antibiotics. Finally, progress was made towards the total synthesis of 26. The de novo biosynthesis of 2,6-dimethyl-5-heptenal (60) by the dendronotid nudibranch, Melibe leonina, was investigated using a stable isotope incorporation experiment with [l,2-¹³C₂]acetate. This study represents the first demonstration of de novo terpene biosynthesis by a dendronotid nudibranch. As well, it is the first example to show that nudibranchs are capable of de novo monoterpene biosynthesis. The work reported with M. leonina supports recent evolutionary theory with regards to nudibranch de novo biosynthesis.Science, Faculty ofChemistry, Department ofGraduat

Palatability and defense of some tropical infaunal worms: alkylpyrrole sulfamates as deterrents to fish feeding

© Inter-Research 2003: www.int-res.comDOI: 10.3354/meps263299Numerous studies have investigated chemical defenses among sessile species growing on hard substrates, but few have addressed this for mobile species in soft-sediment communities. We investigated the palatability and potential chemical defenses of 11 worm species from soft-sediment systems in southern Florida, USA. Three species were unpalatable to the bluehead wrasse Thalassoma bifasciatum. The polychaete Cirriformia tentaculata and the hemichordate Ptychodera bahamensis were uniformly unpalatable. For the polychaete Eupolymnia crassicornis, the exposed tentacles were unpalatable, but the body, which remains protected in a deeply buried tube, was palatable. These unpalatable worms were chemically defended; extracts of C. tentaculata, P. bahamensis, and the tentacles of E. crassicornis deterred fish feeding. For C. tentaculata, bioassay-guided fractionation demonstrated that a mixture of 3 closely related alkylpyrrole sulfamates deterred fish at naturally occurring concentrations (2-n-hexylpyrrole sulfamate [1.6% of worm dry mass], 2-n-heptylpyrrole sulfamate [3.1% dry mass], and 2-n-octylpyrrole sulfamate [0.8% dry mass]). This appears to be the first documentation of characterized natural products defending a marine worm from consumers. For P. bahamensis and the tentacles of E. crassicornis, deterrent effects of crude extracts decomposed before specific compounds could be identifie