Pros and cons of group living in the forest tent caterpillar: separating the roles of silk and of grouping

Group living can incur both benefits and costs, mediated by different mechanisms. In many gregarious caterpillars, collective use of a network of silk trails is thought to improve foraging. Grouping, i.e., close contact with conspecifics, has been postulated to have both positive (thermoregulation and predator defense) and negative (competition and pathogen transmission) effects. The present experiment distinguishes between silk produced by group members and grouping per se in their effects on growth and development of both early and late larval stadia of the forest tent caterpillar [Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae)] in a laboratory context. For both developmental stadia tested, pre‐established silk trails decreased latency to food finding and hence increased food consumption and growth rate. For younger larvae, pre‐established silk also decreased investment in silk production. Grouping young caterpillars accelerated development at the expense of growth, possibly as a mechanism to avoid intraspecific competition in later larval stadia. In older caterpillars, grouping decreased meal duration, suggesting that competition can indeed occur towards the end of larval development, even in the presence of surplus food. This led to a decrease in growth without any effect on instar duration. The benefits of exogenous silk thus decreased during larval development, whereas the costs associated with crowding increased. Ontogenetic shifts in grouping are common in many taxa: the present study is among the first to provide empirical evidence for an adaptive explanation of observed ontogenetic changes in aggregative behavior.     

Analysis of the substrate specificity of α-L-arabinofuranosidases by DNA sequencer-aided fluorophore-assisted carbohydrate electrophoresis

Applied Microbiology and Biotechnology - Carbohydrate-active enzyme discovery is often not accompanied by experimental validation, demonstrating the need for techniques to analyze substrate...     

A Case Study in Serendipity: Environmental Researchers Use of Traditional and Social Media for Dissemination

In the face of demands for researchers to engage more actively with a wider range of publics and to capture different kinds of research impacts and engagements, we explored the ways a small number of environmental researchers use traditional and social media to disseminate research. A questionnaire was developed to investigate the impact of different media as a tool to broker contact between researchers and a variety of different stakeholders (for example, publics, other researchers, policymakers, journalists) as well as how researchers perceive that their use of these media has changed over the past five years. The questionnaire was sent to 504 researchers whose work had featured in a policy-oriented e-news service. 149 valid responses were received (29%). Coverage in traditional media (newspapers, broadcast) not only brokers contact with other journalists, but is a good source of contact from other researchers (n=47, 62%) and members of the public (n=36, 26%). Although the use of social media was limited amongst our sample, it did broker contact with other researchers (n=17, 47%) and the public (n=10, 28%). Nevertheless, few environmental researchers were actively using social media to disseminate their research findings, with many continuing to rely on academic journals and face-to-face communication to reach both academic and public audiences.     

Development of isoform selective PI3-kinase inhibitors as pharmacological tools for elucidating the PI3K pathway

Using a parallel synthesis approach to target a non-conserved region of the PI3K catalytic domain a pan-PI3K inhibitor 1 was elaborated to provide alpha, delta and gamma isoform selective Class I PI3K inhibitors 21, 24, 26 and 27. The compounds had good cellular activity and were selective against protein kinases and other members of the PI3K superfamily including mTOR and DNA-PK.     

Seasonal variation in nutrient limitation of microbial biofilms colonizing organic and inorganic substrata in streams

Humans have increased the availability of nutrients including nitrogen and phosphorus worldwide; therefore, understanding how microbes process nutrients is critical for environmental conservation. We examined nutrient limitation of biofilms colonizing inorganic (fritted glass) and organic (cellulose sponge) substrata in spring, summer, and autumn in three streams in Michigan, USA. Biofilms were enriched with nitrate (NO₃ ⁻), phosphate (PO₄ ³⁻), ammonium (NH₄ ⁺), NO₃ ⁻ + PO₄ ³⁻, NH₄ ⁺ + PO₄ ³⁻, or none (control). We quantified biofilm structure and function as chlorophyll a (i.e., primary producer biomass) and community respiration on all substrata. In one stream, we characterized bacterial and fungal communities on cellulose in autumn using clone library sequencing and denaturing gradient gel electrophoresis to determine if community structure was linked to nutrient limitation status. Despite oligotrophic conditions, primary producer biomass was infrequently nutrient limited. In contrast, respiration on organic substrata was frequently limited by N + P combinations. We found no difference between biofilm response to NH₄ ⁺ versus NO₃ ⁻ enrichment, although the response to both N-species was positively related to water column PO₄ ³⁻ concentrations and temperature. Molecular analysis for fungal community composition suggested no relationship to nutrient limitation, but the dominant members of the bacterial community on cellulose were different on NO₃ ⁻, PO₄³, and NO₃ ⁻ + PO₄ ³⁻ treatments relative to control, NH₄ ⁺, and NH₄ ⁺ + PO₄ ³⁻ treatments, which matched patterns for biofilm respiration rates from each treatment. Our results show discrete patterns of nutrient limitation dependent upon substratum type and season, and imply changes in bacterial community structure and function may be linked following nutrient enrichment in streams.     

Automated Bayesian model development for frequency detection in biological time series

Background

The ability to perform quantitative studies using isotope tracers and metabolic flux analysis (MFA) is critical for detecting pathway bottlenecks and elucidating network regulation in biological systems, especially those that have been engineered to alter their native metabolic capacities. Mathematically, MFA models are traditionally formulated using separate state variables for reaction fluxes and isotopomer abundances. Analysis of isotope labeling experiments using this set of variables results in a non-convex optimization problem that suffers from both implementation complexity and convergence problems.

Results

This article addresses the mathematical and computational formulation of ¹³C MFA models using a new set of variables referred to as fluxomers. These composite variables combine both fluxes and isotopomer abundances, which results in a simply-posed formulation and an improved error model that is insensitive to isotopomer measurement normalization. A powerful fluxomer iterative algorithm (FIA) is developed and applied to solve the MFA optimization problem. For moderate-sized networks, the algorithm is shown to outperform the commonly used 13CFLUX cumomer-based algorithm and the more recently introduced OpenFLUX software that relies upon an elementary metabolite unit (EMU) network decomposition, both in terms of convergence time and output variability.

Conclusions

Substantial improvements in convergence time and statistical quality of results can be achieved by applying fluxomer variables and the FIA algorithm to compute best-fit solutions to MFA models. We expect that the fluxomer formulation will provide a more suitable basis for future algorithms that analyze very large scale networks and design optimal isotope labeling experiments.     

Current methods for molecular typing of Campylobacter species

Campylobacter remains one of the most common bacterial causes of gastroenteritis worldwide. Tracking sources of this organism is challenging due to the large numbers of human cases, and the prevalence of this organism throughout the environment due to growth in a wide range of animal species. Many molecular subtyping methods have been developed to characterize Campylobacter species, but only a few are commonly used in molecular epidemiology studies. This review examines the applicability of these methods, as well as the role that emerging whole genome sequencing technologies will play in tracking sources of Campylobacter spp. infection.     

Proteomics of Colwellia psychrerythraea at subzero temperatures – a life with limited movement,flexible membranes and vital DNA repair

The mechanisms that allow psychrophilic bacteria to remain metabolically active at subzero temperatures result from form and function of their proteins. We present first proteomic evidence of physiological changes of the marine psychrophile Colwellia psychrerythraea 34H (Cp34H) after exposure to subzero temperatures (?1, and ?10°C in ice) through 8 weeks. Protein abundance was compared between different treatments to understand the effects of temperature and time, independently and jointly, within cells transitioning to, and being maintained in ice. Parallel [3H]‐leucine and [3H]–thymidine incubations indicated active protein and DNA synthesis to ?10°C. Mass spectrometry‐based proteomics identified 1763 proteins across four experimental treatments. Proteins involved in osmolyte regulation and polymer secretion were found constitutively present across all treatments, suggesting that they are required for metabolic success below 0°C. Differentially abundant protein groups indicated a reallocation of resources from DNA binding to DNA repair and from motility to chemo‐taxis and sensing. Changes to iron and nitrogen metabolism, cellular membrane structures, and protein synthesis and folding were also revealed. By elucidating vital strategies during life in ice, this study provides novel insight into the extensive molecular adaptations that occur in cold‐adapted marine organisms to sustain cellular function in their habitat.