Joseph Hooker Takes a “Fixed Post”: Transmutation and the “Present Unsatisfactory State of Systematic Botany”, 1844–1860

Joseph Hooker first learned that Charles Darwin believed in the transmutation of species in 1844. For the next 14 years, Hooker remained a “nonconsenter” to Darwin’s views, resolving to keep the question of species origin “subservient to Botany instead of Botany to it, as must be the true relation”. Hooker placed particular emphasis on the need for any theory of species origin to support the broad taxonomic delimitation of species, a highly contentious issue. His always provisional support for special creation waned during the 1850s as he lost faith in its expediency for coordinating the study of plant geography, systematics and physiology. In 1858, Hooker embraced Darwin’s “considerable revolution in natural history,” but only after Darwin had carefully molded his transmutationism to meet Hooker’s exacting specifications.     

Combinatorial biosynthesis of antitumor deoxysugar pathways in Streptomyces griseus: Reconstitution of "unnatural natural gene clusters" for the biosynthesis of four 2,6-D-dideoxyhexoses

Combinatorial biosynthesis was applied to Streptomyces deoxysugar biosynthesis genes in order to reconstitute "unnatural natural gene clusters" for the biosynthesis of four D-deoxysugars (D-olivose, D-oliose, D-digitoxose, and D-boivinose). Expression of these gene clusters in Streptomyces albus 16F4 was used to prove the functionality of the designed clusters through the generation of glycosylated tetracenomycins. Three glycosylated tetracenomycins were generated and characterized, two of which (D-digitoxosyl-tetracenomycin C and D-boivinosyl-tetracenocmycin C) were novel compounds. The constructed gene clusters may be used to increase the capabilities of microorganisms to synthesize new deoxysugars and therefore to produce new glycosylated bioactive compounds.     

Gibberellic acid improves water deficit tolerance in maize plants

The combination effects of water stress and gibberellic acid (GA₃) on physiological attributes and nutritional status of maize (Zea mays L. cv., DK 647 F1) were studied in a pot experiment. Maize plants were grown in the control (well watered WW) and water stress subjected to treated both water stress and two concentrations of gibberellic acid (GA₃ 25 mg L⁻¹, 50 mg L⁻¹). WS was imposed by maintaining the moisture level equivalent to 50 % pot capacity whereas the WW pots were maintained at full pot capacity. Water stress reduced the total dry weight, chlorophyll concentration, and leaf relative water content (RWC), but it increased proline accumulation and electrolyte leakage in maize plants and appears to affect shoots more than roots. Both concentrations of GA₃ (25 and 50 mg L⁻¹) largely enhanced the above physiological parameters to levels similar to control. WS reduced leaf Ca²⁺ and K⁺ concentrations, but exogenous application of GA₃ increased those nutrient levels similar or close to control. Exogenous application of GA₃ improved the water stress tolerance in maize plants by maintaining membrane permeability, enhancing chlorophyll concentration, leaf relative water content (LRWC) and some macro-nutrient concentrations in leaves.     

Enzymatic recovery and purification of polyhydroxybutyrate produced by Ralstonia eutropha

Polyhydroxybutyrate (PHB) is the most studied among a wide variety of polyhydroxyalkanoates, bacterial biodegradable polymers known as potential substitutes for conventional plastics. This work aimed at evaluating the use of enzymes to recover and purify the PHB produced by Ralstonia eutropha DSM545. Screening experiments allowed the selection of trypsin, bromelain and lysozyme among six enzymes, based on their efficiency in lysing cells of a non-PHB producing R. eutropha strain. Then, process conditions for high efficiency in PHB purification from the DSM545 cells were searched for the enzymes previously selected. The best result was achieved with 2.0% of bromelain (enzyme mass per biomass), equivalent to 14.1 U ml(-1), at 50 degrees C and pH 9.0, resulting in 88.8% PHB purity. Aiming at improving the process efficiency and reducing the enzyme cost, experiments were carried out with pancreatin, leading to 90.0% polymer purity and an enzyme cost three times lower than the one obtained with bromelain. The molecular mass analysis of PHB showed no polymer degradation. Therefore, this work demonstrates the potential of using enzymes in order to recover and purify PHB and bacterial biopolymers in general.     

Nitrogen and phosphorus resorption in trees of a Mexican tropical dry forest

Resorption efficiency (RE) and proficiency, foliar nutrient concentrations, and relative soil nutrient availability were determined during 3 consecutive years in tree species growing under contrasting topographic positions (i.e., top vs. bottom and north vs. south aspect) in a tropical dry forest in Mexico. The sites differed in soil nutrient levels, soil water content, and potential radiation interception. Leaf mass per area (g m^–2) increased during the growing season in all species. Soil P availability and mean foliar P concentrations were generally higher at the bottom than at the top site during the 3 years of the study. Leaf N concentrations ranged from 45.4 to 31.4 mg g^–1. Leaf P varied from 2.3 to 1.8 mg g^–1. Mean N and P RE varied among species, occasionally between top and bottom sites, and were higher in the dry than in the wet years of study. Senesced-leaf nutrient concentrations (i.e., a measure of resorption proficiency) varied from 13.7 to 31.2 mg g^–1 (N) and 0.4 to 3.3 mg g^–1 (P) among the different species and were generally indicative of incomplete nutrient resorption. Phosphorus concentrations in senesced leaves were higher at the bottom than at the top site and decreased from the wettest to the the driest year. Soil N and P availability were significantly different in the north- and south-facing slopes, but neither nutrient concentrations of mature and senesced leaves nor RE differed between aspects. Our results suggest that water more than soil nutrient availability controls RE in the Chamela dry forest, while resorption proficiency may be interactively controlled by both nutrient and water availability.     

Structure-activity relationships of a peptide inhibitor of the human FcRn:human IgG interaction

A family of five peptides was previously discovered by phage display techniques that binds to the human neonatal Fc receptor (FcRn) and inhibits the human IgG:human FcRn protein-protein interaction [Proc. Nat. Acad. Sci. U.S.A.2008, 105, 2337-2342]. The consensus peptide motif consists of the sequence GHFGGXY where X is preferably a hydrophobic amino acid, and also includes a disulfide bridge enclosing 11-amino acids in varying positions about the consensus sequence. We describe herein the structure-activity relationships of one of the five peptides in binding to FcRn using surface plasmon resonance and IgG:FcRn competition ELISA assays. Modifications of the peptide length, cyclization, and the incorporation of amino acid substitutions and dipeptide mimetics were studied. The most potent analogs exhibited a 50- to 100-fold improvement of in vitro activity over that of the phage-identified peptide sequence.     

Effect of organic or inorganic trace mineral supplementation on follicular response, ovulation, and embryo production in superovulated Angus heifers

We determined whether source of trace mineral supplementation prior to embryo collection affected embryo production and quality. Angus half-sibling heifers (n = 20) originating from a common herd were assigned to three treatment groups using a 3 × 3 latin square design replicated in time (3×) and space (6× complete and 1× incomplete): (1) heifers received no added mineral to their diet (control; n = 53); (2) heifers received a commercially available organic mineral supplement (organic; n = 52); or (3) heifers received an all inorganic mineral supplement (inorganic; n = 55). All heifers had ad libitum access to hay and were fed a supplement containing corn and soybean meal. Treatments were initiated 23 days prior to embryo recovery. Heifers were given a 45-day adaptation period of no mineral supplementation before initiating a new treatment. Ovarian structures were evaluated using transrectal ultrasonography to determine the presence and number of follicles and CL on each ovary. The mean number of recovered ova/embryos was similar among treatments (4.1 ± 0.7, 3.8 ± 0.7, and 3.3 ± 0.7 for control, inorganic, and organic treatments, respectively), the number of unfertilized oocytes was greater (P < 0.05) for inorganic (2.3 ± 0.5) and control (1.6 ± 0.5) treated heifers than organic (0.4 ± 0.4) treated heifers. No differences among treatments existed for the number of degenerate or transferable embryos, but individual heifer influenced the total number of embryos/ova, unfertilized ova, and transferable embryos recovered. We conclude that heifer accounted for the greatest differences in embryo production and quality. Source of trace mineral supplementation did not significantly alter embryo number or quality in superovulated purebred Angus heifers fed a well-balanced diet, meeting all trace mineral requirements.     

Purification of polyhydroxybutyrate produced by <Emphasis Type="Italic">Burkholderia cepacia</Emphasis> IPT64 through a chemical and enzymatic route

This work aimed at the study of purification of biopolymers produced by Burkholderia cepacia IPT64, through a chemical attack like an adjuvant procedure through chemical and enzymatic route. Enzymatic lysis using protease was run on an enzyme/cell ratio of 0.02. Chemical attacks were performed as pre or post-treatment for enzymatic attacks, using sodium dodecyl sulphate or hydrogen peroxide. The same chemicals and procedures were used alone as a control. Fenton’s reagent was also tested as a chemical treatment. Using only one of the chemicals H₂O₂, Fenton’s reagent or SDS, the purity increase achieved values of 14%, 16% or 23%, respectively. When H₂O₂ or SDS were used as pre-treatment for the enzymatic attack, the results of purity increase achieved values of 58% for H₂O₂/cell ratio between 0.60 and 1.20, and 57% when SDS/cell ratio at 0.56 was used. In the case when H₂O₂ or SDS were used as post-treatment for the enzymatic attack, results of purity increase achieved 60% when the H₂O₂ was used at H₂O₂/cell ratio ranging between 0.30 and 0.60 and 71% when SDS was used at a ratio SDS/cell of 0.56.