The limit of the genetic adaptation to copper in freshwater phytoplankton

Copper is one of the most frequently used algaecides to control blooms of toxic cyanobacteria in water supply reservoirs. Among the negative impacts derived from the use of this substance is the increasing resistance of cyanobacteria to copper toxicity, as well as changes in the community structure of native phytoplankton. Here, we used the ratchet protocol to investigate the differential evolution and maximum adaptation capacity of selected freshwater phytoplankton species to the exposure of increasing doses of copper. Initially, a dose of 2.5 μM CuSO₄·5H₂O was able to completely inhibit growth in three strains of the toxic cyanobacterium Microcystis aeruginosa, whereas growth of the chlorophyceans Dictyosphaerium chlorelloides and Desmodesmus intermedius (represented by two different strains) was completely abolished at 12 μM. A significant increase in resistance was achieved in all derived populations during the ratchet experiment. All the chlorophyceans were able to adapt to up to 270 μM of copper sulfate, but 10 μM was the highest concentration that M. aeruginosa strains were able to cope with, although one of the replicates adapted to 30 μM. The recurrent use and increasing doses of copper in water reservoirs could lead to the selection of copper-resistant mutants of both chlorophyceans and cyanobacteria. However, under high concentrations of copper, the composition of phytoplankton community could undergo a drastic change with cyanobacteria being replaced by copper-resistant chlorophyceans. This result stems from a distinct evolutionary potential of these species to adapt to this substance.     

Evolution of wing polymorphism and genital asymmetry in the thread‐legged bugs of the tribe Metapterini Stål (Hemiptera,Reduviidae, Emesinae) based on morphological characters

Wing polymorphism and asymmetric male genitalia are intriguing morphological phenomena occurring in insects. Among Emesinae, or thread‐legged bugs, the tribe Metapterini Stål exhibits these two interesting morphological attributes. Nonetheless, evolutionary interpretations of these phenomena cannot be put forward because phylogenetic hypotheses for Emesinae are lacking. Thread‐legged bugs are easily recognized among assassin bugs due to their elongated and seemingly delicate body. The tribe Metapterini has 28 genera and approximately 280 described species. The only available phylogenetic hypothesis among Emesinae tribes was proposed by Wygodzinsky (1966), and it hypothesized Deliastini Villiers as the sister group of Metapterini, although this hypothesis has never been tested with cladistic approaches. Recent analyses using character sets of genitalia and prolegs suggest that Metapterini might not be monophyletic. In order to test these ideas, we compiled a morphological dataset of 138 characters that includes external morphological characters, detailed features of prolegs and genitalia of both sexes for Metapterini, which were analysed cladistically including 55 terminals, comprising 24 genera (85.7% of the generic diversity), 43 species of Metapterini and 12 outgroups. Metapterini was recovered as paraphyletic by the inclusion of Bergemesa Wygodzinsky, Palacus Dohrn and Stalemesa Wygodzinsky, all currently assigned to Deliastini. Gardena Dohrn (Emesini) was recovered as the sister group of Metapterini + Deliastini as suggested by Wygodzinsky (1966). Based on these results, we synonymize Deliastini syn. n. with Metapterini sensu n. and propose two new genera: Bacata Castro‐Huertas & Forero gen. n. , for three Andean species previously placed in Liaghinella Wygodzinsky, and Valkyriella Castro‐Huertas & Forero gen. n. for Ghilianella borgmeieri Wygodzinsky. Ancestral state reconstruction of wing polymorphism indicates that males and females were fully winged in the ancestor of Metapterini sensu n. with two independent evolutionary transitions to the apterous and brachypterous conditions. The analysis of the symmetry of the male genitalia shows an ancestor with symmetric male genitalia and two independent emergences of asymmetrical male genitalia in Metapterini.     

Preparation of soybean seed samples for FT-IR microspectroscopy

Typical preparation of seed samples for infrared (IR) microspectroscopy involves imbibition of the seed for varying time periods followed by cryosectioning. Imbibition, however, may initiate germination even at 4° C with associated changes in the chemistry of the sample. We have found that it is possible to section seeds that are sufficiently hard, such as soybeans, on a standard laboratory microtome without imbibition. The use of dry sectioning of unimbibed seeds is reported here, as well as a comparison of different mounting media and modes of analysis. Glycerol, Tissue-Tek, and ethanol were used as mounting media, and the quality of the resulting spectra was assessed. Ethanol was the preferred mountant, because it dried quickly with no residue and thus did not interfere with the spectrum of interest. Analysis in transmission mode using barium fluoride windows to hold the samples was compared with transmission-reflection analysis with sections mounted on special infrared-reflecting slides. The two modes of analysis performed well in different regions of the spectrum. The mode of analysis (transmission vs. transmission-reflection) should be based on the components of greatest interest in the sample.     

Modulating the Expression Strength of the Baculovirus/Insect Cell Expression System: A Toolbox Applied to the Human Tumor Suppressor SMARCB1/SNF5

The human tumor suppressor SMARCB1/INI1/SNF5/BAF47 (SNF5) is a core subunit of the multi-subunit ATP-dependent chromatin remodeling complex SWI/SNF, also known as Brahma/Brahma-related gene 1 (BRM/BRG1)-associated factor (BAF). Experimental studies of SWI/SNF are currently considerably limited by the low cellular abundance of this complex; thus, recombinant protein production represents a key to obtain the SWI/SNF proteins for molecular and structural studies. While the expression of mammalian proteins in bacteria is often difficult, the baculovirus/insect cell expression system can overcome limitations of prokaryotic expression systems and facilitate the co-expression of multiple proteins. Here, we demonstrate that human full-length SNF5 tagged with a C-terminal 3?×?FLAG can be expressed and purified from insect cell extracts in monomeric and dimeric forms. To this end, we constructed a set of donor and acceptor vectors for the expression of individual proteins and protein complexes in the baculovirus/insect cell expression system under the control of a polyhedrin (polh), p10, or a minimal Drosophila melanogaster Hsp70 promoter. We show that the SNF5 expression level could be modulated by the selection of the promoter used to control expression. The vector set also comprises vectors that encode a 3?×?FLAG tag, Twin-Strep tag, or CBP-3?×?FLAG-TEV-ProteinA triple tag to facilitate affinity selection and detection. By gel filtration and split-ubiquitin assays, we show that human full-length SNF5 has the ability to self-interact. Overall, the toolbox developed herein offers the possibility to flexibly select the promoter strength as well as the affinity tag and is suggested to advance the recombinant expression of chromatin remodeling factors and other challenging proteins.     

Feeding innovations and the first coral-feeding fishes

Coral Reefs - Tubelip wrasses were probably the first modern fish group to feed on corals, an ability that has been linked to their unusual lips. However, the only detailed account of these lips is...     

Distribution and diffusivity of a hydrophobic probe molecule in the interior of a membrane: theory and simulation.

We propose a simple model for the distribution of position and orientation and the diffusion of a hydrophobic probe molecule embedded in a membrane. The molecule experiences both a Maier-Saupe orienting potential as well as an enclosing potential of repulsion from the membrane walls. A statistical thermodynamics treatment of the model provides predictions of the location and orientation of the molecule within the membrane. In particular, we evaluate the order parameter of the molecule in terms of the model constants. The diffusivity of the probe is studied by Brownian dynamics simulation. For rotational diffusion, we check an available analytical approximate treatment that allows for the prediction of the dynamics in terms of equilibrium quantities. We also pay attention to quantities related to the initial and mean reorientational rate of the probe. For translational diffusion, we use the simulation results to analyze some general aspects of lateral and transversal diffusion.     

Isolation and expansion of the catabolic potential of a Pseudomonas putida strain able to grow in the presence of high concentrations of aromatic hydrocarbons.

Pseudomonas putida DOT-T1 was isolated after enrichment on minimal medium with 1% (vol/vol) toluene as the sole C source. The strain was able to grow in the presence of 90% (vol/vol) toluene and was tolerant to organic solvents whose log P(ow) (octanol/water partition coefficient) was higher than 2.3. Solvent tolerance was inducible, as bacteria grown in the absence of toluene required an adaptation period before growth restarted. Mg2+ ions in the culture medium improved solvent tolerance. Electron micrographs showed that cells growing on high concentrations of toluene exhibited a wider periplasmic space than cells growing in the absence of toluene and preserved the outer membrane integrity. Polarographic studies and the accumulation of pathway intermediates showed that the strain used the toluene-4-monooxygenase pathway to catabolyze toluene. Although the strain also thrived in high concentrations of m- and p-xylene, these hydrocarbons could not be used as the sole C source for growth. The catabolic potential of the isolate was expanded to include m- and p-xylene and related hydrocarbons by transfer of the TOL plasmid pWW0-Km.