The Probability of a Horizontal Gene Transfer from Roundup Ready® Soybean to Root Symbiotic Bacteria: A Risk Assessment Study on the GSF Lysimeter Station

The gene transfer from glyphosate tolerant soybean to Bradyrhizobium japonicum was evaluated in a free-air lysimeter experiment under natural conditions and increasing selection pressure, to monitor for the probability of horizontal gene transfer (HGT). A large volume lysimeter study that offers conditions comparable to normal farming was conducted in 2004 and 2005 with Roundup Ready® (RR) soybean and Roundup® application according to agricultural practice. Analysis of nodules showed, as expected, the presence of the transgenic 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). However, in bacteroids that were isolated from nodules and then cultivated for several rounds in the presence of high levels of glyphosate, the EPSPS gene could no longer be detected. This indicates no stable HGT transfer of the whole EPSPS gene under field conditions.     

Association of quantum dot nanoparticles with Pseudomonas aeruginosa biofilm

Quantum dots (QDs) of two different surface chemistries (carboxyl [COOH] and polyethylene glycol [PEG] modified) were utilized to determine the impact of surface functionality on QD mobility and distribution in Pseudomonas aeruginosa PAO1 biofilms. Confocal laser scanning microscopy was utilized to evaluate QD association with biofilm components (proteins, cells, and polysaccharides). Quantum dots did not preferentially associate with cell surfaces compared but did colocalize with extracellular proteins in the biofilm matrix. Neither PEG nor COOH QDs were found to be internalized by individual bacterial cells. Neither QD functionality nor flow rate of QD application (0.3 mL min(-1) or 3.0 mL min(-1)) resulted in a marked difference in QD association with P. aeruginosa biofilms. However, center of density determinations indicated COOH QDs could more easily penetrate the biofilm matrix by diffusion than PEG QDs. Biofilms with PEG QDs associated had rougher polysaccharide layers and rougher cell distribution than biofilms with COOH QDs. This work suggests natural biofilms may serve as deposition locations in natural and engineered environmental systems, and biofilm structural parameters may change based on exposure to nanomaterials of varied physical characteristics.     

Microbiological characterization and specific methanogenic activity of anaerobe sludges used in urban solid waste treatment

This study presents the microbiological characterization of the anaerobic sludge used in a two-stage anaerobic reactor for the treatment of organic fraction of urban solid waste (OFUSW). This treatment is one alternative for reducing solid waste in landfills at the same time producing a biogas (CH(4) and CO(2)) and an effluent that can be used as biofertilizer. The system was inoculated with sludge from a wastewater treatment plant (WWTP) (Río Frío Plant in Bucaramanga-Colombia) and a methanogenic anaerobic digester for the treatment of pig manure (Mesa de los Santos in Santander). Bacterial populations were evaluated by counting groups related to oxygen sensitivity, while metabolic groups were determined by most probable number (MPN) technique. Specific methanogenic activity (SMA) for acetate, formate, methanol and ethanol substrates was also determined. In the acidogenic reactor (R1), volatile fatty acids (VFA) reached values of 25,000 mg L(-1) and a concentration of CO(2) of 90%. In this reactor, the fermentative population was predominant (10(5)-10(6)MPN mL(-1)). The acetogenic population was (10(5)MPN mL(-1)) and the sulphate-reducing population was (10(4)-10(5)MPN mL(-1)). In the methanogenic reactor (R2), levels of CH(4) (70%) were higher than CO(2) (25%), whereas the VFA values were lower than 4000 mg L(-1). Substrate competition between sulphate-reducing (10(4)-10(5)MPN mL(-1)) and methanogenic bacteria (10(5)MPN mL(-1)) was not detected. From the SMA results obtained, acetoclastic (2.39 g COD-CH(4)g(-1)VSS(-1)day(-1)) and hydrogenophilic (0.94 g COD-CH(4)g(-1)VSS(-1)day(-1)) transformations as possible metabolic pathways used by methanogenic bacteria is suggested from the SMA results obtained. Methanotrix sp., Methanosarcina sp., Methanoccocus sp. and Methanobacterium sp. were identified.     

Genetic diversity of Nymphon (Arthropoda: Pycnogonida: Nymphonidae) along the Antarctic Peninsula with a focus on Nymphon australe Hodgson 1902

Sea spiders are conspicuous, and often abundant, members of the Antarctic benthic community. Nymphonidae (Pycnogonida) in Southern Ocean waters comprise over 240 species which are often difficult to assign due to their intraspecific ‘highly variable’ morphology. In particular, Nymphon australe, the numerically dominant species in Antarctic waters is known to have a high level of phenotypic variation in external morphology and is also reported to have a circumpolar distribution. Circumpolarity seems contradictory to the pycnogonid’s brooding lifestyle and presumably limited dispersal. Here we examine the genetic diversity of several Nymphon species collected in the Antarctic Peninsular region. Concomitantly, we assess the genetic structure of N. australe to gain insight into Nymphon dispersal capacity. Cytochrome c oxidase subunit I (COI) and 16S ribosomal gene data suggest a recent common history and/or recent gene-flow of N. australe populations across nearly 800 km of the Antarctic Peninsula. Furthermore, these data support that the Antarctic Peninsula region may hold two previously unrecognized species of Nymphon. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The public good dilemma of a non-renewable common resource: A look at the facts of artisanal gold mining

Millions of people worldwide are involved in artisanal and small-scale gold mining. Many of them live in conditions of poverty and insalubrities due to the mercury amalgamation of gold and the application of other rudimentary techniques. In spite of this, the sector has been nearly overlooked by resource economists. In this paper we analyze the sector based on a survey of the existing literature. We find some commonalities of artisanal and small-scale gold mining in different countries of the developing world as follows: low levels of mechanization and technology, labor intensiveness, low awareness of environmental degradation, poor training, high transience among some miners, and lack of financial savings. Moreover, with these commonalities in mind, we present some topics and challenges for a research agenda in the field of environmental, ecological, and development economics.