Sexual selection and speciation: Issues raised by Hawaiian Drosophila

The Drosophila fauna of Hawaii is extraordinarily diverse, representing about 25% of the world's described species. The most notable characteristics which differentiate the species in Hawaii are morphological and behavioral ones used in courtship and mating. These flies are excellent model species for investigating the evolution of sexually selected traits. Hypotheses regarding the associations between species formation and mating behaviour have been formulated as a result of work on this group, leading to further empirical and theoretical research.     

Uptake and utilization of lipids by Paramecium tetraurelia

Uptake rates of a variety of 14C-labeled fatty acids and complex lipids by Paramecium tetraurelia during 48 h of log-phase growth varied. Fatty acid uptake was maximal during lag phase of growth when phagosome (food vacuole) formation was minimal. Food vacuole formation was shown to be suppressed by the presence of exogenous lipids and by starvation. The rates of uptake of lipids were significantly greater than those of small organic compounds such as amino acids, cyclitols, fatty acid precursors and metabolic intermediates. Significant amounts of radioactivity from 14C-labeled fatty acids were metabolized to 14CO2. The uptake rates of different saturated, straight-chain fatty acids of even carbon numbers were different and were not correlated with chain length, results suggesting that the primary mechanism for uptake of these compounds was neither by bulk transport nor simple diffusion and that carrier-mediated processes could possibly be involved.     

Pleomorphism and acetylene-reducing activity of free-living rhizobia.

Cowpea-type Rhizobium sp. strain 32H1 and Rhizobium japonicum USDA 26 and 110 grown on a glutamate-mannitol-gluconate agar medium showed increases in the number of pleomorphic cells coincident with their acetylene-reducing activity. Pleomorphs appeared to be inhibited in growth nonuniformly, because acetylene-reducing cultures were mixtures of rod, branched (V, Y, and T), and other irregularly shaped cells. In contrast, strain USDA 10 consistently failed to reduce acetylene, even though it also could grow and yield pleomorphic cells under various conditions. With minimal inhibitory supplements (5 micrograms per ml of medium) of nalidixic acid and novobiocin as cell division inhibitors, an increase in pleomorphic cells was observed, but the inhibited cultures displayed lower acetylene-reducing activity. A study of pleomorphic cells derived in different ways indicated that not all pleomorphs reduce acetylene.     

Oleic acid transformations by selected strains of Sphingobacterium thalpophilum and Bacillus cereus from composted manure

In a survey of 186 randomly selected microbial strains isolated from composted manure, 63 transformed oleic acid into three types of products: hydroxy fatty acid, fatty amide, and less polar oleyl lipid. Selection of oleic acid-transforming microorganisms was enhanced in nutrient agar supplemented with 0.1% (vol/vol) oleic acid at pH 7.2. Most of the 63 diverse isolates elicited inconsistent and poorly reproduced transformations. However, strains 142b (NRRL B-14797) transformed oleic acid to 10-hydroxystearic acid consistently, and strain 229b (NRRL B-14812) produced an octadecenamide. Taxonomic studies indicated that NRRL strain B-14797, possessing 1,3-dihydroxy-2-amino-15-methylhexadecane and sphinganine bases, was closely related to Sphingobacterium thalpophilum, and NRRL B-14812 was identified as Bacillus cereus.     

Fatty acid metabolism in Paramecium. Oleic acid metabolism and inhibition of polyunsaturated fatty acid synthesis by triparanol

Paramecium requires oleic acid for growth and can grow in media containing no other fatty acids. In the present study, we have shown that this ciliate utilized oleate mainly as a carbon and energy source, even though this fatty acid was the only substrate available for synthesis of polyunsaturated fatty acids. Culture growth was inhibited by the addition of the drug triparanol. Triparanol decreased the formation of polyunsaturated fatty acids from oleate by preventing desaturation to form the dienoic acid, linoleate. Triparanol inhibition resulted in an altered phospholipid fatty acyl composition, an increased fragility and an altered behavioral response of the cells to a depolarizing stimulation solution. Therefore, although most of the dietary oleate was not used by the cells for polyunsaturated fatty acid synthesis, the desaturation of oleic acid was critical for normal culture growth, cell integrity and swimming behavior, all of which are expected to be dependent on normal membrane lipid composition.     

The self-association of jack bean urease and its modification by silver ions.

At low ionic strength urease has been found to dissociate at protein concentrations below 1 × 10⁸m. The inhibition of enzyme activity by Ag⁺ has been used to demonstrate this. The inhibition by Ag⁺ has been shown to be independent of dissociation but, at dilutions where dissociation occurs, silver ion modifies the process. Urease is aggregated by Ag⁺ at high Ag⁺:protein ratios. Such inactive aggregates can be solubilized and reactivated by dithiothreitol. Further evidence has been obtained indicating the similarity of the (8n) and (16n) forms of urease. The phenomena of inhibition and aggregation in the presence of the heavy metal ion have been shown to be separate processes.     

Fibrous Material in Feedlot Waste Fermented by Trichoderma viride

Trichoderma viride QM9123 fermented fiber isolated from feedlot waste at concentrations up to 16.7% solids. The fermented fiber solids decreased by 32%, and carbohydrate decreased by 60%. Cellulotyic enzyme production was better with fiber substrates that had been alkali pretreated and had a lower hemicellulose-to-cellulose ratio.     

Sterol composition of Pneumocystis jirovecii with blocked 14alpha-demethylase activity

Several drugs that interact with membrane sterols or inhibit their syntheses are effective in clearing a number of fungal infections. The AIDS-associated lung infection caused by Pneumocystis jirovecii is not cleared by many of these therapies. Pneumocystis normally synthesizes distinct C28 and C29 24-alkylsterols, but ergosterol, the major fungal sterol, is not among them. Two distinct sterol compositional phenotypes were previously observed in P. jirovecii. One was characterized by delta7 C28 and C29 24-alkylsterols with only low proportions of higher molecular mass components. In contrast, the other type was dominated by high C31 and C32 24-alkylsterols, especially pneumocysterol. In the present study, 28 molecular species were elucidated by nuclear magnetic resonance analysis of a human lung specimen containing P. jirovecii representing the latter sterol profile phenotype. Fifteen of the 28 had the methyl group at C-14 of the sterol nucleus and these represented 96% of the total sterol mass in the specimen (excluding cholesterol). These results strongly suggest that sterol 14alpha-demethylase was blocked in these organisms. Twenty-four of the 28 were 24-alkylsterols, indicating that methylation of the C-24 position of the sterol side chain by S-adenosyl-L-methionine:sterol C-24 methyl transferase was fully functional.     

Comprehensive and definitive structural identities of Pneumocystis carinii sterols

Pneumocystis causes a type of pneumonia in immunodeficient mammals, such as AIDS patients. Mammals cannot alkylate the C-24 position of the sterol side chain, nor can they desaturate C-22. Thus, the reactions leading to these sterol modifications are particularly attractive targets for the development of drugs against fungal and protozoan pathogens that make them. In the present study, the definitive structures of 43 sterol molecular species in rat-derived Pneumocystis carinii were elucidated by nuclear magnetic resonance spectroscopy. Ergosterol, Delta(5,7) sterols, trienes, and tetraenes were not among them. Most (32 of the 43) were 24-alkylsterols, products of S-adenosyl-L-methionine:C-24 sterol methyl transferase (SAM:SMT) enzyme activity. Their abundance is consistent with the suggestion that SAM:SMT is highly active in this organism and that the enzyme is an excellent anti-Pneumocystis drug target. In contrast, the comprehensive analysis strongly suggest that P. carinii does not form Delta(22) sterols, thus C-22 desaturation does not appear to be a drug target in this pathogen. The lanosterol derivatives, 24-methylenelanost-8-en-3 beta-ol and (Z)-24-ethylidenelanost-8-en-3 beta-ol (pneumocysterol), previously identified in human-derived Pneumocystis jiroveci, were also detected among the sterols of the rat-derived P. carinii organisms.