Duplication of leucyl-tRNA synthetase in an archaeal extremophile may play a role in adaptation to variable environmental conditions.

Aminoacyl-tRNA synthetases (aaRSs) are ancient enzymes that play a fundamental role in protein synthesis. They catalyze the esterification of specific amino acids to the 3'-end of their cognate tRNAs and therefore play a pivotal role in protein synthesis. Although previous studies suggest that aaRS-dependent errors in protein synthesis can be beneficial to some microbial species, evidence that reduced aaRS fidelity can be adaptive is limited. Using bioinformatics analyses, we identified two distinct leucyl-tRNA synthetase (LeuRS) genes within all genomes of the archaeal family Sulfolobaceae. Remarkably, one copy, designated LeuRS-I, had key amino acid substitutions within its editing domain that would be expected to disrupt hydrolytic editing of mischarged tRNALeu and to result in variation within the proteome of these extremophiles. We found that another copy, LeuRS-F, contains canonical active sites for aminoacylation and editing. Biochemical and genetic analyses of the paralogs within Sulfolobus islandicus supported the hypothesis that LeuRS-F, but not LeuRS-I, functions as an essential tRNA synthetase that accurately charges leucine to tRNALeu for protein translation. Although LeuRS-I was not essential, its expression clearly supported optimal S. islandicus growth. We conclude that LeuRS-I may have evolved to confer a selective advantage under the extreme and fluctuating environmental conditions characteristic of the volcanic hot springs in which these archaeal extremophiles reside.

Preliminary water quality assessment of Spunky Bottoms restored wetland.

The approximately 1200-acre "Spunky Bottoms" wetland in Southern Illinois has been undergoing restoration to conditions prior to levying of the Illinois River and draining of adjacent floodplain for intensive agriculture (circa 1900). As part of a long-term water quality impact assessment of this restoration project, baseline water quality monitoring was conducted soon after restoration began. During this baseline/preliminary assessment, water samples were taken every 2-4 weeks from 10 sampling wells and seven surface water sites throughout the wetlands area for a period of 18 months. Measured parameters include nutrients (nitrate (NO3-) and phosphate (PO4(3-)), cations and anions (SO4(2-), Cl-, Na+, K+, Mg2+, Ca2+) commonly found in surface and well water, trace metals (Al, Cd, Cu, Fe, Mn, Ni, Pb, Se, Zn), total dissolved solids (TDS), pH, and trace organics (triazine herbicides and their metabolites). In general, highest concentrations of ions were found in the southwest and northeast perimeter of the wetland area for both surface and ground water samples. Primarily low concentrations of heavy metals and organic compounds were found throughout the wetland sampling area. Distribution of NO3--N suggests that this restored wetland, even at its infant age, may still contribute to biogeochemical (particularly N) element cycling. Continued monitoring and further research is necessary to determine long-term specific contribution of restored wetland to biogeochemical cycles.