Effect of Rifampicin on Expression of some Episomal Genes in <Emphasis Type="Italic">E. coli</Emphasis>

F, F′ and R factors are closed circular molecules with molecular weights ranging from 5–100×10⁶. They code for a number of different functions, including pili formation, fertility, autonomous replication, restriction of certain bacteriophages and exclusion of other extrachromosomal elements.     

Highlights for Agave Productivity

Agaves can grow in marginal arid and semiarid lands where their special ecological and physiological adaptations to environmental conditions give them the potential to produce substantial biomass. Agave americana was the first agave species shown to be a Crassulacean Acid Metabolism plant, with CO₂ uptake occurring primarily at night and with high water‐use efficiency (photosynthesis/transpiration). A. salmiana and A. mapisaga can have high nocturnal net CO₂ uptake rates and high productivities averaging 40 tonnes dry weight ha^?1 yr^?1. Agaves can benefit from the increases in temperature and atmospheric CO₂ levels accompanying global climate change. An Environmental Productivity Index can predict the effects of soil and environmental factors on CO₂ uptake and hence on the regions appropriate for cultivating agaves. In turn, their increased cultivation can support the production of innovative earth‐friendly commodities that can be used as new bioenergy feedstocks.     

Bodo sp., a Free-Living Flagellate, Expresses Divergent Proteolytic Activities from the Closely Related Parasitic Trypanosomatids

ABSTRACT. We report the characterization of cell-associated and extracellular peptidases of Bodo sp., a free-living flagellate of the Bodonidae family, order Kinetoplastida, which is considered ancestral to the trypanosomatids. This bodonid isolate is phylogenetically related to Bodo caudatus and Bodo curvifilus . The proteolytic activity profiles of Bodo sp. were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis containing co-polymerized gelatin, casein, hemoglobin, or bovine serum albumin as substrates. The enzymatic complex degraded gelatin better in acidic pH, and under these conditions four proteolytic bands (120, 100, 90, and 75 kDa) were detected in the cellular or extracellular extracts. Two peptidases (250 and 200 kDa) were exclusively detected with the substrate casein. All these enzymes belong to the serine peptidase class, based on inhibition by aprotinin and phenylmethylsulfonyl fluoride. This is the first biochemical characterization of peptidases in a free-living Bodo sp., potentially providing insight into the physiology of these protozoa and the evolutionary importance of peptidases to the order Kinetoplastida as some of these enzymes are important virulence factors in pathogenic trypanosomatids.     

Fine-scale microhabitat selection in a bromeliad-dwelling jumping spider (Salticidae)

Although a wide variety of arthropods specialize on a specific host plant, little is known about the evolution of host–plant specialization in spiders. In several regions of South America, the Neotropical jumping spider Psecas chapoda associates with Bromelia balansae , a rosette-shaped plant that does not accumulate rain water in phytotelmata. We conducted experiments using bromeliad species with distinct architectures that were uncommon in the geographic range of P. chapoda to investigate the level of spider specialization in microhabitat structure. We also tested the influence of phytotelmata and foliar spines on host plant selection. B. balansae , Ananas comosus and Aechmea distichantha (tank-bromeliad), which share similar traits (e.g. long and narrow leaves), were colonized in similar frequencies. Aechmea fasciata , a tank-bromeliad that has short and broad leaves, was never colonized by these spiders, and Aechmea blanchetiana , tank-bromeliad with long and broad leaves, was only colonized infrequently. The removal of foliar spines did not affect the number of P. chapoda on B. balansae . Our findings suggest that microhabitat specialization by P. chapoda is based on rosette and leaf architectures. This unusual specialization likely evolved because the bromeliads with such architecture (i.e. B. balansae ) typically dominate the biogeographic area of P. chapoda , and because this microhabitat provides specific benefits to spiders, as shelter, and as foraging and reproductive sites.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 653–662.     

Baseline Levels of Potentially Toxic Elements in Pampas Soils

The soils of the Pampas are thought to be generally non-contaminated but there is growing evidence of trace element accumulation at some specific sites. The goal of this study was to measure the current levels of the main Potentially Toxic Elements (PTE) in the top horizon and in specific soil profiles so that we would establish the baseline concentrations of these elements. Eighty-eight top soils and three soil profiles were sampled. The samples were acid digested. Arsenic, boron, barium, cadmium, cobalt, chromium, copper, lead, manganese, mercury, molybdenum, nickel, silver, selenium and zinc were determined with inductively coupled argon plasma emission spectrometry (ICPES).

All of the values found are within the normal range for uncontaminated soils as reported from several continents. Elements with high environmental risk potential are lower than the admissible range of the European Union and some of them are orders of magnitude lower than those of the United States Environmental Protection Agency (US-EPA) 501 levels. Potentially Toxic Elements contents increased with depth or showed a maximum concentration at the B2 horizon. This is related to the parent material and the pedogenetic processes but not to recent contamination. Soil profiles showed higher concentrations of PTE in clayey horizons. However, these relationships did not appear in top soil samples in any soil Great Group studied. The shown data establishes a baseline for PTE concentrations for Pampas soils.     

The potential of Miscanthus to sequester carbon in soils: comparing field measurements in Carlow,Ireland to model predictions

Growing bioenergy crops such as Miscanthus has the potential to mitigate atmospheric carbon dioxide emissions by the replacement of fossil fuels and by storing carbon (C) in the soil due to land use change. Here we compare direct measurements of soil organic C fractions made in Carlow (Ireland) to model predictions made by RothC and a cohort model. Our results show that when Miscanthus is grown on land previously under arable agriculture, the soil organic C will increase to a level above that of native pasture, as Miscanthus organic material is shown to have a slow decomposition rate. In addition we demonstrate that for measured organic C, fractions of different lability are similar to the C pools used in RothC. Using the model predictions from RothC and Miscanthus yields from MISCANFOR, we predict that in Ireland, changing the land use from arable to Miscanthus plantations has the potential to store between 2 and 3 Mg C ha^?1 y^?1 depending on the crop yield and the initial soil organic C level.