Knockout of pgdS and ggt genes improves γ‐PGA yield in B. subtilis

One of the emerging biopolymers that are currently under active investigation is bacterial poly(γ‐glutamic acid) (γ‐PGA). However, before its full industrial exploitation, a substantial increase in microbial productivity is required. γ‐PGA obtained from the Bacillus subtilis laboratory strain 168 offers the advantage of a producer characterized by a well defined genetic framework and simple manipulation techniques. In this strain, the knockout of genes for the major γ‐PGA degrading enzymes, pgdS and ggt, leads to a considerable improvement in polymer yield, which attains levels analogous to the top wild γ‐PGA producer strains. This study highlights the convenience of using the laboratory strain of B. subtilis over wild isolates in designing strain improvement strategies aimed at increasing γ‐PGA productivity. Biotechnol. Bioeng. 2013; 110: 2006–2012. © 2013 Wiley Periodicals, Inc.     

A geographic mosaic of evolutionary lineages within the insular endemic newt Euproctus montanus

Islands are hotspots of biodiversity, with a disproportionately high fraction of endemic lineages, often of ancient origin. Nevertheless, intra‐island phylogeographies are surprisingly scarce, leading to a scanty knowledge about the microevolutionary processes induced on island populations by Plio‐Pleistocene climatic oscillations, and the manner in which these processes contributed to shape their current genetic diversity. We investigated the phylogeography, historical demography and species distribution models of the Corsican endemic newt Euproctus montanus (north‐western Mediterranean). As for many island endemics, the continuous distribution of E. montanus throughout its range has hitherto been considered as evidence for a single large population, a belief that also guided the species' categorization for conservation purposes. Instead, we found a geographic mosaic of ancient evolutionary lineages, with five main clades of likely Pliocene origin (2.6–5.8 My), all but one restricted to northern Corsica. Moreover, the copresence between main lineages in the same population was limited to a single case. As also suggested by growing literature on intra‐island phylogeographic variation, it seems that the extensive use of simplifying assumption on the population structure and historical demography of island populations—both in theoretical and applicative studies—should be carefully reconsidered, a claim that is well exemplified by the case presented here.     

Synthesis and biological evaluation against Leishmania amazonensis of a series of alkyl-substituted benzophenones

Nine O-alkyl and O-prenyl derivatives were synthesized from commercial 2,4-dihydroxybenzophenone, 4,e4,4′-dihydroxybenzophenone and were evaluated for their leishmanicidal activity against promastigote forms of Leishmania amazonensis, as well their toxicity in murine macrophages. All derivatives exhibited better biological activity than their hydroxylated benzophenones precursors, and new compound LFQM-123 (3c) was 250-fold more active than its precursor 4,4′-dihydroxybenzophenone (3). Moreover, some of the results were comparable to the standard drug Amphotericin B, suggesting that the increase in lipophilicity could facilitate protozoa membrane permeation. In this study we confirmed that benzophenone derivatives exhibit leishmanicidal properties, with relatively low toxicity, and thus could be exploited as promise prototypes for the design and development of new drug for the treatment of leishmaniasis.     

Dual on-off and off-on switchable oligoaziridine biosensor

A water-soluble biocompatible aziridine-based biosensor with pendant anthracene units was synthesized by radicalar polymerization of N-substituted aziridines in supercritical carbon dioxide. The binding ability of the sensor towards a series of metal ions was examined by comparing the fluorescence intensities of the solutions before and after the addition of 100 equivalents of a solution of the metal ion chloride salt. A fast, simple and highly optical sensitive dual behavior, "off-on" and "on-off" response, was observed after the biosensor was exposed to the metal cations in aqueous solution. Zinc presented the highest fluorescence enhancement (turn-on) and copper presented the highest fluorescence quenching (turn-off). The response time was found to be instantaneous and the detection limit was achieved even in the presence of excess metal cation competitors. By using immunofluorescence microscopy it was also shown that oligoaziridine acts as an "on-off" probe through highly sensitive (detection limit of 1.6nM), selective and reversible binding to copper anions under physiologic conditions using living Human Fibroblast cells. The stoichiometry for the reaction of the biosensor with Cu(2+) was determined by a Job plot and indicates the formation of an oligoaziridine-Cu(2+) 1:2 adduct.     

Seed structure, germination, and reserve mobilization in Butia capitata (Arecaceae)

Butia capitata is a palm tree endemic to the Cerrado biome of Brazil and has significant potential for ornamental and food uses. In this work, we characterized the structures of the seeds and seedlings of this species to identify anatomical aspects related to its pronounced dormancy and determine the processes involved in reserve mobilization. Intact seeds, and seeds from which the operculum had been removed, were allowed to germinate and their morphology, physiology, anatomy, and histochemistry, together with those of the seedlings, were followed for 30 days. The seed coat was found to be rich in phenolic compounds and not lignified. The endosperm contains abundant protein and lipidic reserves, and the embryo has additional starch reserves. Germination occurred only in seeds with their opercula removed and involved the elongation of the cotyledon cells and meristematic activity in the “M zone” located between the embryonic axis and the proximal extremity of the embryo. The mobilization of embryonic reserves initiates during the first phase of imbibition, while the mobilization of endosperm reserves represents a post-germination event associated with the formation of a secretory epidermis and aerenchyma and the vascularization of the haustorium. Seeds with intact opercula did not germinate, but demonstrated embryonic reserve mobilization and cell elongation, indicating that dormancy in B. capitata is related to the incapacity of the embryo to dislocate the operculum.     

Arsenic toxicity: cell signalling and the attenuating effect of nitric oxide in Eichhornia crassipes

Nitric oxide (NO) is an important molecule involved in the perception of stress induced by toxic compounds such as arsenic (As). The present study investigated the role of NO applied as sodium nitroprusside (SNP) in cell signalling and the ability of NO to attenuate the toxic effects of As (in the form of sodium arsenate) in water hyacinth (Eichhornia crassipes). Water hyacinth plants were collected and assigned to one of the following treatments: control; 100 μM SNP; 20 μM As; or 20 μM As + 100 μM SNP. The plants remained under these conditions for 0, 4, 12, and 24 h. After each time interval, the plants were collected and As absorption, production of reactive oxygen species (ROS), integrity of membranes, and antioxidant enzyme activities were evaluated. The plants were able to absorb and accumulate large amounts of As, even after only four hours of exposure to the pollutant. The absorption and bioaccumulation factor of As was even greater when plants were exposed to both As and SNP. The accumulation of As triggered increases in ROS production and cell membrane damage. In the presence of SNP, the tolerance index to As increased and damage was mitigated. Therefore, from the present work, it was possible to conclude that exogenous NO influenced the ability of plants to tolerate As; this finding has implications for phytoremediation in areas contaminated by As.