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.

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.

Notre Dame, Notre Dame, IN 46556-0309, USA Rhodococcus sp. strain lGTS8 (ATCC 53968) is able to utilize dibenzothiophene (DBT) as a sole source of sulphur. The carbon skeleton of DBT is not metabolized and is conserved as 2-hydroxybiphenyl (HBP), which accumulates in the medium. This phenotype is due to the expression of the plasmidencoded DBT-desulphurization (dsz) operon, which encodes three proteins, DszA, B and C. In this paper it is shown, using r5S]DBT radiolabelling studies, that sulphur is released in the form of inorganic sulphite. The pathway of DBT desulphurization is described in detail. In summary, DszC catalyses the stepwise S-oxidation of DBT, first to dibenzothiophene 5-oxide (DBTO) and then to dibenzothiophene 5,s-dioxide (DBTO,) ; DszA catalyses the conversion of DBTO, to 2-(2'-hydroxyphenyl)benzene sulphinate (HBPSi') and DszB catalyses the desulphination of HBPSi' to give HBP and sulphite. Studies with cell-free extracts show that DszA and DszC, but not DszB, require NADH for activity. 180,-labelling studies show that each incorporated oxygen atom is derived directly from molecular oxygen. These results are consistent with the role of DszC as a mono-oxygenase, of DUA as an apparently unique enzyme which catalyses the reductive hydroxylation of DBTO, leading to cleavage of the thiophene ring, and of DszB as an aromatic sulphinic acid hydrolase.

Automobile catalytic converters are dispersing platinum-group elements (PGEs) Rh, Pt, and Pd into the environment (1-3). This paper represents the first detailed study to assess the PGE content of soils and grasses from U.S. roadsides. These soils were analyzed using cation exchange pretreatment and ultrasonic nebulizer-ICP-MS (4). Highway and several urban sites showed Pt abundances of 64-73 ng/g immediately adjacent to the roadside, with corresponding Pd and Rh abundances of 18-31 ng/g and 3-7 ng/g, respectively. All Pt and most Pd and Rh abundances are statistically above local background soil values. Platinum, Rd, and Rh show positive correlations with traffic-related elements (Ni, Cu, Zn, and Pb) but no correlations with nontraffic-related elements (Y, Ga). Iridium and Ru show no correlations with any of these trace elements. These PGE abundances are comparable to European studies (5-7) and are approaching concentrations that would be economically viable to recover. This study also demonstrates transport of Pt statistically above background more than 50 m from the roadside. Further study is necessary to see how mobile the PGEs are in roadside environments, but these initial data indicate only Pt is taken up by plants.