The evolution of new enzyme function: lessons from xenobiotic metabolizing bacteria versus insecticide-resistant insects

Here, we compare the evolutionary routes by which bacteria and insects have evolved enzymatic processes for the degradation of four classes of synthetic chemical insecticide. For insects, the selective advantage of such degradative activities is survival on exposure to the insecticide, whereas for the bacteria the advantage is simply a matter of access to additional sources of nutrients. Nevertheless, bacteria have evolved highly efficient enzymes from a wide variety of enzyme families, whereas insects have relied upon generalist esterase-, cytochrome P450- and glutathione-S-transferase-dependent detoxification systems. Moreover, the mutant insect enzymes are less efficient kinetically and less diverged in sequence from their putative ancestors than their bacterial counterparts. This presumably reflects several advantages that bacteria have over insects in the acquisition of new enzymatic functions, such as a broad biochemical repertoire from which new functions can be evolved, large population sizes, high effective mutation rates, very short generation times and access to genetic diversity through horizontal gene transfer. Both the insect and bacterial systems support recent theory proposing that new biochemical functions often evolve from ‘promiscuous’ activities in existing enzymes, with subsequent mutations then enhancing those activities. Study of the insect enzymes will help in resistance management, while the bacterial enzymes are potential bioremediants of insecticide residues in a range of contaminated environments

Middle Ordovician acritarchs and problematic organic-walled microfossils from the Saq-Hanadir transitional beds in the QSIM-801 well, Saudi Arabia

Core samples from the QSIM-801 water well, drilled in central Saudi Arabia, cover a 93-foot interval spanning the transition between the Sajir Member of the Saq Formation, that consists mainly of sandstones of tidal sand flat environments, and the Hanadir Member of the Qasim Formation, characterized by argillaceous graptolitic mudstones, corresponding to a tidal delta front. The samples contain abundant, exceptionally well-preserved and diverse palynomorphs, which include cryptospores, acritarchs and chitinozoans, other problematic organic-walled microfossils as well as other organic particles such as cuticle-like fragments. The studied interval is biostratigraphically well constrained by the presence of chitinozoans of the formosa and pissotensis Zones of late-early to late Darriwilian age (Middle Ordovician) in the uppermost Saq Formation and Hanadir Member. The biostratigraphic age of the Sajir Member considered to span the Dapingian–Darriwilian boundary, is re-discussed based on the results herein. The uppermost part of the Sajir Member yielded the ichnofossil, Phycodes fusiforme. Acritarch assemblages from the Sajir Member of the Saq Formation are poorly diversified and dominated by sphaeromorphs. More diverse assemblages of acritarchs, associated with enigmatic forms, occur in the Hanadir Member of the Qasim Formation. The contact between the two formations and the transition between the palynomorph assemblages are sharp, suggesting a stratigraphic hiatus. A quantitative analysis allows us to discuss the paleoenvironmental changes and possibly climatic changes associated with an hypothesis of ice house conditions during this period. Among the diagnostic acritarch taxa observed are Frankea breviuscula, F. longiuscula, Baltisphaeridium ternatum, Dasydorus cirritus, Dicrodiacrodium ancoriforme, Poikilofusa ciliaris, Pterospermopsis colbathii and Uncinisphaera fusticula. These are associated with other typical forms known to range across the Lower–Middle Ordovician boundary, such as Aremoricanium rigaudae, Aureotesta clathrata, Barakella fortunata, B. rara, Baltisphaeridium klabavense, Glaucotesta latiramosa and Striatotheca spp. Galeate and peteinoid acritarchs are also well represented, as well as tiny forms of ultraplanctonic size. Three new species of acritarchs are proposed: Frankea longiuscula var. darriwilense var. nov, Micrhystridium regulum sp. nov, and Tyrannus proteus sp. nov. Repeated occurrences throughout the section of cryptospores, problematic microfossils such as organic filaments, cuticle-like tissues, striated and pigmented leiospheres frequently in clusters, are interpreted to reflect recurrent terrestrial and freshwater inputs in the depositional environment. Single-specimen, high-resolution analyses using Confocal Laser Scanning Microscopy on the enigmatic form Tyrannus proteus sp. nov. show fluorescence emission spectra and microstructural properties significantly different from those of typical marine acritarchs from the same levels

Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere

The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon) in the diversification of the marine biosphere. Nutrient availability and phytoplankton stoichiometry played a critical role in the initial diversification of the marine biosphere during the Neoproterozoic. Initial biosphere expansion during this time resulted in the massive sequestration of nutrients into biomass which, along with the geologically slow input of nutrients from land, set the stage for severe nutrient limitation and relatively constant marine biodiversity during the rest of the Paleozoic. Given the slow nutrient inputs from land and low recycling rates, the growth of early-to-middle Paleozoic metazoans remained limited by their having to expend energy to first “burn off” (respire) excess carbon in food before the associated nutrients could be utilized for growth and reproduction; the relative equilibrium in marine biodiversity during the Paleozoic therefore appears to be real. Limited nutrient availability and the consequent nutrient imbalance may have delayed the appearance of more advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests, greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability. During the Meso-Cenozoic, rising oxygen levels, the continued nutrient input from land, and, especially, increasing rates of bioturbation, enhanced nutrient availability, increasing the nutrient content of phytoplankton that fueled the diversification of the Modern Fauna

Practices as a unit for design: an exploration of theoretical guidelines in a study on bathing

The sustainability challenges facing society today require approaches that look beyond single product- user interactions. Focusing on socially shared practices—e.g. cooking, laundering—has been identified as a promising direction. Building on a growing body of research in sustainable HCI that takes practices as unit of analysis, this article explores what it means to take practices as a unit of design. Drawing on theories of practice, it proposes that practice-oriented design approaches should: involve bodily performance, create crises of routine and generate a variety of performances. These guidelines were integrated into a Generative Improv Performances (GIP) approach, entailing a series of performances by improvisation actors with low- fidelity prototypes in a lab environment. The approach was implemented in an empirical study on bathing. Although the empirical example does not deal with common types of interactive technologies, the guidelines and GIP approach offer sustainable HCI a way to think beyond immediate interactions and to conceptualize change on a practice level

Early diagenetic formation of carbonates in a clastic-dominated ramp environment impacted by synsedimentary faulting-induced fluid seepage – Evidence from the Late Jurassic Boulonnais Basin (N France)

International audienceThe Late Jurassic deposits of the Boulonnais area (N-France) represents the proximal lateral-equivalent of the Kimmeridge Clay Formation; they accumulated on a clastic-dominated ramp subject to synsedimentary faulting in relation with the northward propagation of the Atlantic rifting. Within the terrigenous accumulations, some carbonate objects are visible at various conspicuous levels: oyster patch reefs and fine-grained carbonate beds, either continuous, or more or less nodular. Preliminary studies demonstrated that the carbonate beds of the Bancs Jumeaux Formation as well as the carbonate matrix of the oyster patch reefs are of diagenetic origin. In this paper, we extend the study to many other limestone beds of the Boulonnais with mud- or wackestone texture, examining facies and microfacies through various techniques as well as geochemical data (O, C and S stable isotopes, major and trace elements). We conclude that all examined carbonate bodies are of early diagenetic origin and that they precipitated at, or close to, the sea bed, from seawater mixing with ascending fluids containing isotopically light carbon of organic origin. Fluid circulation was probably induced by the extensional block-faulting segmentation of the northern margin of the Boulonnais Basin in Late Jurassic times. Fluid seepages were either channelized along fault planes or more diffuse, as illustrated by the model we propose