Carboxylic ester hydrolases from hyperthermophiles

Carboxylic ester hydrolyzing enzymes constitute a large group of enzymes that are able to catalyze the hydrolysis, synthesis or transesterification of an ester bond. They can be found in all three domains of life, including the group of hyperthermophilic bacteria and archaea. Esterases from the latter group often exhibit a high intrinsic stability, which makes them of interest them for various biotechnological applications. In this review, we aim to give an overview of all characterized carboxylic ester hydrolases from hyperthermophilic microorganisms and provide details on their substrate specificity, kinetics, optimal catalytic conditions, and stability. Approaches for the discovery of new carboxylic ester hydrolases are described. Special attention is given to the currently characterized hyperthermophilic enzymes with respect to their biochemical properties, 3D structure, and classification

Handbook of Environmental Chemistry

The assessment of bioaccumulation processes plays a significant role in the evaluation of chemical risks. The awareness of long-lasting and often irreversible effects of bioaccumulative chemicals on ecological and human targets encouraged the inclusion of bioaccumulation assessment in many national and international legislative frameworks. At the same time, various experimental and modelling approaches have been developed to estimate bioaccumulation metrics such as the bioaccumulation factor (BAF) or the biomagnification factor (BMF). In this chapter, the main processes governing bioaccumulation phenomena in selected aquatic organisms (phytoplankton, invertebrate and fish) and in terrestrial mammals are described, in particular those implemented in the corresponding models available in MERLIN-Expo tool for exposure assessment. The main objective is to describe the development of bioaccumulation models for organic and inorganic contaminants which takes into account recent progresses and which satisfactorily describes bioaccumulation of contaminants along food webs including phytoplankton, invertebrate and fish species for surface waters, and mammals for terrestrial systems, and also allowing dynamic and stochastic assessment according to MERLIN-Expo modelling features. The coupling of different aquatic biota models allows to recreate aquatic food web of different dimensions and complexity, while the coupling of terrestrial mammal model with plant models available in MERLIN-Expo permits to simulate the transfer of contaminants along simplified terrestrial food chains

Toxic effects of molluscicidal baits to the terrestrial isopod Porcellionides pruinosus (Brandt, 1833)

Purpose Methiocarb and metaldehyde are the most common molluscicides applied in agricultural and horticultural fields in Portugal and elsewhere in Europe. The application of molluscicidal baits to control slug and snail populations can pose a threat to non-target organisms like terrestrial isopods, because they are detritivorous and may feed on the toxic baits applied to the soil surface. The aim of this work was to evaluate the effects and understand the modes of action of these molluscicides to terrestrial isopods. Materials and methods In this study, the terrestrial isopod Porcellionides pruinosus was exposed to these two molluscicides, and the time to lethality was evaluated. Biochemical indicators (biomarkers) are known to provide early warning signs of environmental pollution or stress conditions to the organisms, by measuring cellular or molecular responses of the target organism to xenobiotic agents. Therefore, to evaluate modes of action and effects and also to see if biomarkers can be used as early warning tools in molluscicidal exposures, three different enzymes, glutathione S-transferase (GST), acetylcholinesterase (AChE) and catalase (CAT), were analysed upon single exposures and binary mixtures tests. Results and discussion These two molluscicides showed to be of extreme concern regarding terrestrial isopods, as all animals died after 24 h of exposure to methiocarb, and only 20% survived after 56 h of exposure to metaldehyde. Results indicate that the carbamate methiocarb inhibited significantly AChE activity, but no effects were observed in CAT and GST levels. The exposure to metaldehyde had no effects on AChE, but a decrease in GST activity as well as a general increase in CAT activity was observed at the higher exposure period tested (32 h). The combined exposure of the two molluscicides resulted in a general decrease in AChE and CAT activity, but no visible effects were observed in terms of GST activity. Conclusions The LT50 values found in the single exposures to both molluscicides were very low, especially in the case of the carbamate methiocarb. The use of several biomarkers was a suitable tool to understand the mode of action of these two molluscicides in this isopod species

The effect of a glyphosate-based herbicide on acetylcholinesterase (AChE) activity, oxidative stress, and antioxidant status in freshwater amphipod: Gammarus pulex (Crustacean)

This study had determined the effect of glyphosate-based herbicide (GBH) on acetylcholinesterase (AChE) enzyme activity, oxidative stress, and antioxidant status in Gammarus pulex. Firstly, the 96-h LC50 value of glyphosate on G. pulex was determined and calculated as 403 μg/L. Subsequently, the organisms were exposed to sub-lethal concentrations (10, 20, and 40 μg/L) of the determined GHB for 24 and 96 h. The samples were taken from control and GBH-treated groups at 24 and 96 h of study and analysed to determine the malondialdehyde (MDA) and reduced glutathione (GSH) levels, the AChE, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) enzyme activities. In the G. pulex exposed to GBH for 24 and 96 h, the MDA level increased significantly (p < 0.05). The GSH level, the AChE, the CAT, and the GPx activities decreased compared with the control group (p < 0.05). G. pulex exposure to GBH for 24 h showed a temporary reduction in the SOD. GBH exposure led to oxidative stress in the G. pulex as well as affected the cholinergic system of the organism. These results indicated that the parameters measured may be important indicators of herbicide contamination in G. pulex

Connectivity and complex systems: learning from a multi-disciplinary perspective

In recent years, parallel developments in disparate disciplines have focused on what has come to be termed connectivity; a concept used in understanding and describing complex systems. Conceptualisations and operationalisations of connectivity have evolved largely within their disciplinary boundaries, yet similarities in this concept and its application among disciplines are evident. However, any implementation of the concept of connectivity carries with it both ontological and epistemological constraints, which leads us to ask if there is one type or set of approach(es) to connectivity that might be applied to all disciplines. In this review we explore four ontological and epistemological challenges in using connectivity to understand complex systems from the standpoint of widely different disciplines. These are: (i) defining the fundamental unit for the study of connectivity; (ii) separating structural connectivity from functional connectivity; (iii) understanding emergent behaviour; and (iv) measuring connectivity. We draw upon discipline-specific insights from Computational Neuroscience, Ecology, Geomorphology, Neuroscience, Social Network Science and Systems Biology to explore the use of connectivity among these disciplines. We evaluate how a connectivity-based approach has generated new understanding of structural-functional relationships that characterise complex systems and propose a ‘common toolbox’ underpinned by network-based approaches that can advance connectivity studies by overcoming existing constraints