Ionic liquids (ILs) are novel organic salts with a wide liquid range that have enormous potential for industrial use as ''green'' chemicals. Varying the cationic and anionic components can alter IL properties and toxicities. Before the likely industrial release of ILs into the environment, it is necessary to determine their toxic and antimicrobial properties. As a measure of microbial toxicity of imidazolium and pyridinium ILs with varying alkyl chain lengths, we investigated Vibrio fischeri using the Microtox method. An increase in alkyl group chain length as well as an increase in the number of alkyl groups substituted on the cation ring corresponded with an increase in toxicity. Varying the anion identity did not significantly alter toxicity. We then examined the antimicrobial effects of 1000 ppm of butyl-, hexyl-and octyl-imidazolium and pyridinium bromide ILs on the growth of a group of microorganisms representing a variety of physiological and respiratory capabilities. In general, hexyl-and octyl-imidazolium and pyridinium bromides had significant antimicrobial activity to pure cultures of Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Pseudomonas fluorescens and Saccharomyces cerevisiae. Butyl-imidazolium and pyridinium bromides were less antimicrobial than ILs with longer alkyl chain lengths to all microorganisms examined. However, the most significant antimicrobial activity was observed in tests with B. subtilis. This research provides toxicity and antimicrobial information about ILs, prior to their widespread use and release. This type of proactive approach can aid in the prevention of pollution, and avoid costs of future clean-up, and provide information about the ''green'' nature of practical industrial solvents.

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Ionic liquids (ILs) are novel organic salts that have enormous potential for industrial use as green replacements for harmful volatile organic solvents. Varying the cationic components can alter the chemical and physical properties of ILs, including solubility, to suit a variety of industrial processes. However, to complement designer engineering, it is crucial to proactively characterize the biological impacts of new chemicals, in order to fully define them as environmentally friendly. Before introduction of ILs into the environment, we performed an analysis of the biodegradability of six ILs by activated sludge microorganisms collected from the South Bend, Indiana wastewater treatment plant. We examined biodegradability of 1-butyl, 1-hexyl and 1-octyl derivatives of 3-methyl-imidazolium and 3-methyl-pyridinium bromide compounds using the standard Organisation for Economic Cooperation and Development dissolved organic carbon Die-Away Test, changes in total dissolved nitrogen concentrations, and 1H-nuclear magnetic resonance analysis of initial and final chemical structures. Further, we examined microbial community profiles throughout the incubation period using denaturing gradient gel electrophoresis (DNA-PCR-DGGE). Our results suggest that hexyl and octyl substituted pyridinium-based ILs can be fully mineralized, but that imidazolium-based ILs are only partially mineralized. Butyl substituted ILs with either cation, were not biodegradable. Biodegradation rates also increase with longer alkyl chain length, which may be related to enhanced selection of a microbial community. Finally, DGGE analysis suggests that certain microorganisms are enriched by ILs used as a carbon source. Based on these results, we suggest that further IL design and synthesis include pyridinium cations and longer alkyl substitutions for rapid biodegradability.

This report details the outcome the first meeting of the Earth Microbiome Project to discuss sample selection and acquisition. The meeting, held at the Argonne National Laboratory on Wednesday October 6th 2010, focused on discussion of how to prioritize environmental samples for sequencing and metagenomic analysis as part of the global effort of the EMP to systematically determine the functional and phylogenetic diversity of microbial communities across the world.

Investigating the interactions between nanoscale materials and microorganisms is crucial to provide a comprehensive, proactive understanding of nanomaterial toxicity and explore the potential for novel applications. It is well known that nanomaterial behavior is governed by the size and composition of the particles, though the effects of small differences in size toward biological cells have not been well investigated. Palladium nanoparticles (Pd NPs) have gained significant interest as catalysts for important carbon-carbon and carbon-heteroatom reactions and are increasingly used in the chemical industry, however, few other applications of Pd NPs have been investigated. In the present study, we examined the antimicrobial capacity of Pd NPs, which provides both an indication of their usefulness as target antimicrobial compounds, as well as their potency as potential environmental pollutants. We synthesized Pd NPs of three different well-constrained sizes, 2.0±0.1 nm, 2.5±0.2 nm and 3.1±0.2 nm. We examined the inhibitory effects of the Pd NPs and Pd2+ ions toward gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus) bacterial cultures throughout a 24 hour period. Inhibitory growth effects of six concentrations of Pd NPs and Pd2+ ions (2.5×10−4, 10−5, 10−6, 10−7, 10−8, and 10−9 M) were examined. Our results indicate that Pd NPs are generally much more inhibitory toward S. aureus than toward E. coli, though all sizes are toxic at ≥10−5 M to both organisms. We observed a significant difference in size-dependence of antimicrobial activity, which differed based on the microorganism tested. Our work shows that Pd NPs are highly antimicrobial, and that fine-scale (<1 nm) differences in size can alter antimicrobial activity.