Terence J. Evens

A solution to the problem of ion confounding in experimental biology

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Sensory Imbalance as Mechanism of Orientation Disruption in the Leafminer Phyllocnistis citrella: Elucidation by Multivariate Geometric Designs and Response Surface Models

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Mono- and digalactosyldiacylglycerol composition of dinoflagellates. IV. Temperature-induced modulation of fatty acid regiochemistry as observed by electrospray ionization/mass spectrometry

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Are Hofmeister Series Relevant to Modern Ion-Specific Effects Research?

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LIPID COMPOSITION OF CHLORARACHNIOPHYTES (CHLORARACHNIOPHYCEAE) FROM THE GENERA BIGELOWIELLA, GYMNOCHLORA, AND LOTHARELLA1

Experimental designs developed to address mixtures are suited ideally to many areas of experimental biology, including pheromone blend studies, because such designs address the confounding of proportionality and concentration intrinsic to factorial and one-factor-at-a-time designs. Geometric multivariate designs coupled with response surface modeling allowed us to identify optimal blends of a two-component pheromone for attraction and trap disruption of the leafminer moth, Phyllocnistis citrella, a major pest in citrus growing areas around the world. Field trials confirmed that the natural 3:1 blend of (Z,Z,E)-7,11,13-hexadecatrienal:(Z,Z)-7,11-hexadecadienal was most effective as an attractant for male moths. However, the response surface generated in mating orientation trials revealed that the triene component alone was more effective than the natural blend in disrupting trap catch. Each individual component was effective at disrupting orientation in field trials, but (Z,Z,E)-7,11,13-hexadecatrienal was approximately 13 times more effective, at the same concentration, compared with (Z,Z)-7,11-hexadecadienal alone. In addition, the application of geometric design and response surface modeling to field studies provided insight into a possible mechanism of mating disruption and supported sensory imbalance as the operating mechanism for this species.

A data mining approach to dinoflagellate clustering according to sterol composition: correlations with evolutionary history

Members of the dinoflagellate genus Pyrocystis possess forms of mono- and digalactosyldiacylglycerol (MGDG and DGDG, respectively) that have the C20 fatty acid eicosapentaenoic acid [20:5(n–3)] at the sn-1 position and either octadecapentaenoic acid [18:5(n–3)] or octadecatetraenoic acid [18:4(n–3)] at the sn-2 position. We have examined the effect of growth at 15°C, 20°C, and 25°C on modulation of the fatty acids associated with MGDG and DGDG in two strains of each of three species of Pyrocystis, P. fusiformis, P. lunula, and P. noctiluca and have observed using positive-ion electrospray ionization/mass spectrometry (ESI/MS) and electrospray ionization/mass spectrometry/mass spectrometry (ESI/MS/MS) that modulation of the sn-2 fatty acid of DGDG was the only consistent, statistically significant temperature response across all three species. Only one strain of P. lunula displayed a statistically significant temperature-induced modulation of MGDG. In addition, the effect of growth temperature on two forms of the recently identified lipid, trigalactosyldiacylglycerol (TGDG), was examined; TGDG displayed a statistically significant temperature response in only one strain of P. noctiluca. The results presented herein demonstrate how DGDG is modified preferentially over MGDG and TGDG in response to growth temperature by modulating the sn-2 fatty acid of DGDG between the 18:5(n–3) and 18:4(n–3) forms, while the sn-1 fatty acid, 20:5(n–3), remained constant.

Quantification of nutrient-replete growth rates in five-ion hyperspace for Chlorella vulgaris (Trebouxiophyceae) and Peridinium cinctum (Dinophyceae)

Ion-specific effects underlie a vast array of physicochemical and biological phenomena ranging from human physiology to biotechnology to ecology. These effects have traditionally been quantified by measuring the response of interest in a series of salt solutions at multiple concentrations; pH has consistently been shown to be of primary concern. However, salt-based approaches violate critical tenets of proper experimental design and introduce confounding errors that make it impossible to quantify ion-specific effects. For example, pH is a variable dependent on the type and concentration of ions in a solution, but is typically treated as an independent factor, thus confounding experiments designed to determine ion-specific effects. We examined the relevancy of ion-specific effects research in relation to these concepts and demonstrated how these ideas impact protein precipitation and enzyme activity. Based on these results, we present a conceptual and experimental framework of general applicability for proper quantification of ion-specific effects.

Artificial Diet Optimized to Produce Normative Adults of Diaprepes abbreviatus (Coleoptera: Curculionidae)

The Chlorarachniophyceae are unicellular eukaryotic algae characterized by an amoeboid morphology that may be the result of secondary endosymbiosis of a green alga by a nonphotosynthetic amoeba or amoeboflagellate. Whereas much is known about the phylogeny of chlorarachniophytes, little is known about their physiology, particularly that of their lipids. In an initial effort to characterize the lipids of this algal class, four organisms from three genera were examined for their fatty acid and sterol composition. Fatty acids from lipid fractions containing chloroplast‐associated glycolipids, storage triglycerides, and cytoplasmic membrane‐associated polar lipids were characterized. Glycolipid‐associated fatty acids were of limited composition, principally eicosapentaenoic acid [20:5(n‐3)] and hexadecanoic acid (16:0). Triglyceride‐associated fatty acids, although minor, were found to be similar in composition. The polar lipid fraction was dominated by lipids that did not contain phosphorus and had a more variable fatty acid composition with 16:0 and docosapentaenoic acid [22:5(n‐3)] dominant along with a number of minor C18 and C20 fatty acids. Crinosterol and one of the epimeric pair poriferasterol/stigmasterol were the sole sterols. Several genes required for synthesis of these sterols were computationally identified in Bigelowiella natans Moestrup. One sterol biosynthesis gene showed the greatest similarity to SMT1 of the green alga, Chlamydomonas reinhardtii. However, homologues to other species, mostly green plant species, were also found. Further, the method used for identification suggested that the sequences were transferred to a genetic compartment other than the likely original location, the nucleomorph nucleus.

Applying Clustering and Phylogeny Analysis to Study Dinoflagellates Based on Sterol Composition

This study examined the sterol compositions of 102 dinoflagellates using clustering and cluster validation techniques, as a means of determining the relatedness of the organisms. In addition, dinoflagellate sterol-based relationships were compared statistically to 18S rDNA-based phylogenetic relationships using the Mantel test. Our results indicated that the examined dinoflagellates formed six clusters based on sterol composition and that several, but not all, dinoflagellate genera, which formed discrete clusters in the 18S rDNA-based phylogeny, shared similar sterol compositions. This and other correspondences suggest that the sterol compositions of dinoflagellates are explained, to a certain extent, by the evolutionary history of this lineage.

Bud emergence and shoot growth from mature citrus nodal stem segments

The effects of five ions, , , K+, Na+ and Cl−, on growth rates were quantified for Chlorella vulgaris (Trebouxiophyceae) and Peridinium cinctum (Dinophyceae) in batch cultures. A five-dimensional, experimental design hypervolume was defined by five-ion mixture vectors projected across a total ion concentration gradient of 1 to 30 mM to quantify growth rates in relation to N:P ratios and primary bulk solution ions. Both C. vulgaris and P. cinctum exhibited very similar, positive responses to cations and negative responses to anions. It was determined that total ion concentration for these five ions, from 1 to 30 mM, did not directly affect growth rate for either alga, although it did play an interactive role with several ions. No truly ‘optimal’ N : P ratio was identified for either alga. Instead, regions of fast growth rates were mapped within the multivariate experimental design space, or ‘hypervolumes’, that encompassed relatively broad ranges of N:P ratios. This illustrates the fact that optimality is highly contextual and directly dependent on the total ion complement of any given medium. Our results also show that pH is a poor indicator of growth medium quality and should not be considered an independent factor. This study is the first set of unconfounded, ion-specific experiments with algae that we are aware of. The data suggest that we need to reconsider the discussion surrounding ‘optimal’ ratios and concentrations of nutrients/ions in relation to growth to encompass the hyperdimensionality of media defined by multiple ion vectors. This ‘ionic context’ is extremely important to algal physiology, has broad implications for questions of nutrient requirements, and needs to be further explored.