Organic solvent tolerance of halophilic α-amylase from a Haloarchaeon, Haloarcula sp. strain S-1

A halophilic archaeon, Haloarcula sp. strain S-1, produced extracellular organic solvent-tolerant -amylase. Molecular mass of the enzyme was estimated to be 70 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This amylase exhibited maximal activity at 50°C in buffer containing 4.3 M NaCl, pH 7.0. Moreover, the enzyme was active and stable in various organic solvents (benzene, toluene, and chloroform, etc.). Activity was not detected at low ionic strengths, but it was detected in the presence of chloroform at low salt concentrations. On the other hand, no activity was detected in the presence of ethyl alcohol and acetone.     

Biogeochemistry and microbial community composition in sea ice and underlying seawater off East Antarctica during early spring

Pack ice, brines and seawaters were sampled in October 2003 in the East Antarctic sector to investigate the structure of the microbial communities (algae, bacteria and protozoa) in relation to the associated physico-chemical conditions (ice structure, temperature, salinity, inorganic nutrients, chlorophyll a and organic matter). Ice cover ranged between 0.3 and 0.8 m, composed of granular and columnar ice. The brine volume fractions sharply increased above −4°C in the bottom ice, coinciding with an important increase of algal biomass (up to 3.9 mg C l⁻¹), suggesting a control of the algae growth by the space availability at that period of time. Large accumulation of NH₄ ⁺ and PO₄ ³⁻ was observed in the bottom ice. The high pool of organic matter, especially of transparent exopolymeric particles, likely led to nutrients retention and limitation of the protozoa grazing pressure, inducing therefore an algal accumulation. In contrast, the heterotrophs dominated in the underlying seawaters.     

Plant community structure in an oligohaline tidal marsh

An oligohaline tidal marsh on the northern shore of Lake Pontchartrain, LA was characterized with respect to the distributions and abundances of plant species over spatial and temporal gradients using Detrended Correspondence Analysis (DCA). In addition, the species distributions were correlated to several physical environmental factors using Detrended Canonical Correspondence Analysis (DCCA). The distributions of species were best correlated with distance from Lake Pontchartrain, and to a lesser extent with elevation and substrate organic matter. They were least correlated with mean soil salinity (referred to here as background salinity). Of the three mid-seasonal dominant species, the perennial grass, Spartina patens, is the most salt tolerant and was found closest to the lake. Further inland the dominant perennial was Sagittaria lancifolia, which has a salt tolerance less than that of Spartina patens. The perennial sedge, Cladium jamaicense, which is the least salt tolerant of the three, was dominant furthest inland. Background salinity levels were generally low (<5 ppt.) and did not explain species distributions. We hypothesize that the distribution of species is regulated by occasional storm-generated salt pulses that generate strong, short-lived salinity gradients as a function of distance from the lake. Biotic interactions likely also play a role in structuring the plant community. The distributions of several annuals depended on the size and life history of the mid-seasonal dominant perennials. Most of the annuals frequently co-occurred with Sagittaria lancifolia, which was the shortest in stature and had the least persistent canopy of the three mid-seasonal dominant perennials.Abbreviations DCA Detrended Correspondence Analysis - DCCA Detrended Canonical Correspondence Analysis     

皖南休宁新元古界-下寒武统沉积岩的有机碳同位素记录

皖南休宁县蓝田地区震旦系皮园村组和下寒武统荷塘组主要由硅质岩和黑色页岩组成。皮园村组硅质岩的分析结果表明:δ13Corg分析值落在-36.39‰—-31.45‰范围之内,而且从该剖面的底部到顶部呈现出逐步下降的趋势,可能归之于大气和海洋中O2/CO2比值上升,生物氧化作用增强所致;有机碳(TOC)含量<1%,有机氮(TON)含量<1‰,两者均处于蓝田地区埃迪卡拉系—下寒武统地层的最低值,证明晚震旦世时期该地区海洋生物产量比前期(蓝田期)海洋产量显著下降,可能归之于海水加深,不利于海洋生物的繁殖。荷塘组黑色页岩的δ13Corg分析值落在-33‰—-31‰范围之内,TOC和TON含量与皮园村组比较有大幅度提高,尤其黑色页岩下段TOC含量达到13.85%,证明早寒武世海洋生物得到了大发展。由于新元古代冰期后海洋藻类的大量涌现和早寒武世海洋生物得到大发展,生物光合作用产生大量的O2,导致大气和海水中O2/CO2比值进一步升高,可能是引发“寒武纪生物大爆发”的重要因素。     

Hydrothermal synthesis and characterization of a zinc-substituted gallium phosphite, [H3N(CH2)2NH3]1/2 · [GaZn(HPO3)3(H2O)2]

An organically templated zinc-substituted gallium phosphite, [H₃N(CH₂)₂NH₃]_1/2 · [GaZn(HPO₃)₃(H₂O)₂] was synthesized under mild hydrothermal conditions in the presence of ethylenediamine (en) as structure-directing agent and characterized by single-crystal X-ray diffraction analysis. It crystallizes in the orthorhombic space group Pbcn with unit cell parameters: a = 18.6146(10) Å, b = 11.0454(6) Å, c = 10.9074(4) Å, V = 2242.62(19) Å³ and Z = 8. This compound has a three-dimensional framework built up from secondary building units (SBU) of Ga(III) (or Zn(II)) and HPO₃ pseudopyramid by sharing vertices. The structure displays a two-dimensional channel system running along the [0 0 1] and [0 1 0] direction with 5-, 8- and 10-membered rings. The diprotonated ethylenediamine template molecules are located in the channels. In this structure, some of the Ga(III) sites are occupied by Zn(II) atoms. The compound was also characterized by IR spectroscopy, inductively coupled plasma (ICP), X-ray photoelectron spectra (XPS), differential thermal and thermogravimetric analyses.     

Role of aluminum-binding ligands in aluminum resistance of Eucalyptus camaldulensis and Melaleuca cajuputi

We investigated the roles of Al-binding ligands in Al exclusion from roots and in internal Al detoxification in roots as Al resistance mechanisms in two Al-resistant Myrtaceae trees, Eucalyptus camaldulensis Dehnh. and Melaleuca cajuputi Powell. The amounts of ligands secreted from roots and contained in root tips of these species were compared with those of an Al-sensitive species, Melaleuca bracteata F. Muell., after the roots were exposed to 0 or 1 mM AlCl₃ solution. Secretion of well-known ligands (citrate, oxalate, and malate) from roots under Al treatment was low in all species. However, in E. camaldulensis, the Al-binding capacity of root exudates under Al treatment was considerable and was higher than that in M. bracteata. Gel filtration chromatography revealed that a low-molecular-weight Al-binding ligand was secreted from roots in response to Al only in E. camaldulensis. On the other hand, the Al-binding capacity of cell sap in root tips under Al treatment was similar for the resistant and sensitive species. These results suggest that Al exclusion by secretion of the unknown low-molecular-weight Al-binding ligand from roots contributes to the Al resistance of E. camaldulensis, whereas M. cajuputi has developed Al-resistance mechanisms other than secretion of ligands from roots or concentration of internal ligands in root tips.     

Octahedral rhenium cluster complexes with organic ligands: Synthesis, structure and properties of [Re6Q8(3,5-Me2PzH)6]Br2 · 2(3,5-Me2PzH) (Q = S, Se)

Two new octahedral cluster complexes - [Re₆S₈(3,5-Me₂PzH)₆]Br₂ · 2(3,5-Me₂PzH) (1) and [Re₆Se₈(3,5-Me₂PzH)₆]Br₂ · 2(3,5-Me₂PzH) (2), where 3,5-Me₂PzH is 3,5-dimethylpyrazole, have been synthesized using reaction of rhenium chalcobromide complexes Cs₄[Re₆S₈Br₆] · 2H₂O and Cs₃[Re₆Se₈Br₆] · H₂O, respectively, with molten 3,5-dimethylpyrazole. Both compounds synthesized were characterized by X-ray single-crystal diffraction and chemical analysis, IR and luminescent spectra.     

NOB suppression and adaptation strategies in the partial nitrification–Anammox process for a poultry manure anaerobic digester

Poultry manure contains high levels of ammonia, which result in a suboptimal bioconversion to methane in anaerobic digesters (AD). A simultaneous process of nitrification, Anammox and denitrification (SNAD) in a continuous granular bubble column reactor to treat the anaerobically digested poultry manure was implemented. Thus, two strategies to achieve high efficiencies were proposed in this study: (1) ammonia overload to suppress nitrite oxidizing bacteria (NOB) and (2) gradual adaptation of the partial nitrification–Anammox (PN–A) biomass to organic matter. During the NOB-suppression stage, microbial and physical biomass characterizations were performed and the NOB abundance decreased from 31.3% to 3.3%. During the adaptation stage, with a nitrogen loading rate of 0.34 g L⁻¹ d⁻¹, a hydraulic retention time of 1.24 d and an influent COD/N ratio of 2.63 ± 0.02, a maximum ammonia and total nitrogen removal of 100% and 91.68% were achieved, respectively. The relative abundances of the aerobic and the anaerobic ammonia-oxidizing bacteria were greater than 35% and 40% respectively, during the study. These strategies provided useful design tools for the efficient removal of nitrogen species in the presence of organic matter.     

Geographic range, impact, and parasitism of lepidopteran species associated with the invasive weed Lantana camara in South Africa

Six isolates of Trichoderma were screened for antagonism to Armillaria in tea stem sections buried in the soil. The inability of Armillaria to invade Trichoderma-colonized stem sections and the reduction of its viability in the plant materials following invasion of these by Trichoderma were used as indicators of antagonism. Four isolates of the species Trichoderma harzianum significantly (P<0.001) reduced the incidence of the pathogen in the plant materials. Isolate T4 completely eliminated the pathogen from plant materials in sterile soil and also antagonized two different isolates of the pathogen in nonsterile soil. Application of this T. harzianum isolate to the soil as a wheat bran culture significantly (P<0.001) reduced viability of Armillaria in woody blocks of inoculum. Soil amendment with coffee pulp also reduced the inoculum viability but did not affect the incidence of Trichoderma in the blocks of inoculum. We conclude that the direct application of wheat bran-formulated T. harzianum into soil surrounding woody Armillaria inoculum sources can suppress the pathogen. Further, no organic amendment is needed to enhance development of the antagonist in the soil as a pre-requisite to suppressing the pathogen.     

Molecular modeling of the human multidrug resistance protein 1 (MRP1/ABCC1)

Multidrug resistance protein 1 (MRP1/ABCC1) is a 190 kDa member of the ATP-binding cassette (ABC) superfamily of transmembrane transporters that is clinically relevant for its ability to confer multidrug resistance by actively effluxing anticancer drugs. Knowledge of the atomic structure of MRP1 is needed to elucidate its transport mechanism, but only low resolution structural data are currently available. Consequently, comparative modeling has been used to generate models of human MRP1 based on the crystal structure of the ABC transporter Sav1866 from Staphylococcus aureus. In these Sav1866-based models, the arrangement of transmembrane helices differs strikingly from earlier models of MRP1 based on the structure of the bacterial lipid transporter MsbA, both with respect to packing of the twelve helices and their interactions with the nucleotide binding domains. The functional importance of Tyr³²⁴ in transmembrane helix 6 predicted to project into the substrate translocation pathway was investigated.