Characterization of recA genes and recA mutants of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae

Summary DNA fragments carrying the recA genes of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae were isolated by complementing a UV-sensitive recA ^– Escherichia coli strain. Sequence analysis revealed that the coding region of the R. meliloti recA gene consists of 1044 by coding for 348 amino acids whereas the coding region of the R. leguminosarum bv. viciae recA gene has 1053 bp specifying 351 amino acids. The R. meliloti and R. leguminosarum bv. viciae recA genes show 84.8% homology at the DNA sequence level and of 90.1% at the amino acid sequence level. recA ^– mutant strains of both Rhizobium species were constructed by inserting a gentamicin resistance cassette into the respective recA gene. The resulting recA mutants exhibited an increased sensitivity to UV irradiation, were impaired in their ability to perform homologous recombination and showed a slightly reduced growth rate when compared with the respective wild-type strains. The Rhizobium recA strains did not have altered symbiotic nitrogen fixation capacity. Therefore, they represent ideal candidates for release experiments with impaired strains.The accession numbers: X59956 R. LEGUMINOSARUM REC A ALAS-DNA; X59957 R. MELITOTI REC A ALAS-DNA     

Effects of NH+4-N and NO+3-N on growth and metabolism of Sphagnum magellanicum

Photosynthetic CO₂-fixation, chlorophyll content, growth rate and nitrate reductase activity were used to examine the influence of NH⁺₄-N and NO⁻₃-N on Sphagnum magellanicum cultivated under defined conditions in phytotrons. NO⁻₃-concentrations up to 322 μ M were found to be favourable. Increased NH⁺₄ concentrations, however, resulted in growth inhibition and decreased chlorophyll content at concentrations ≧ 255 μ M ; e.g. 600 μ M NH⁺₄ caused a 20% reduction of nitrate reductase activity and net photosynthesis. For raised bog Sphagna an improved standard nutrient solution is proposed with the following ion concentrations (μ M ): 55 Na⁺; 17 K⁺; 95 NH⁺₄; 22 Ca²⁺; 22 Mg²⁺; 2 Fe³⁺; 20 Cl⁻; 100 NO⁻₃; 57 SO^2-₄; 7.4 H₂PO⁻₄; trace elements: A-Z solution (Hoagland) 50 μl 1000 ml⁻¹; pH 5.8.     

Comparison of parameters estimated from A/Ci and A/Cc curve analysis

The parameters estimated from traditional A/C _i curve analysis are dependent upon some underlying assumptions that substomatal CO₂ concentration (C _i) equals the chloroplast CO₂ concentration (C _c) and the C _i value at which the A/C _i curve switches between Rubisco- and electron transport-limited portions of the curve (C _i-t) is set to a constant. However, the assumptions reduced the accuracy of parameter estimation significantly without taking the influence of C _i-t value and mesophyll conductance (g _m) on parameters into account. Based on the analysis of Larix gmelinii’s A/C _i curves, it showed the C _i-t value varied significantly, ranging from 24 Pa to 72 Pa and averaging 38 Pa. t-test demonstrated there were significant differences in parameters respectively estimated from A/C _i and A/C _c curve analysis (p<0.01). Compared with the maximum ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation rate (V_cmax), the maximum electron transport rate (J_max) and J_max/V_cmax estimated from A/C _c curve analysis which considers the effects of g _m limit and simultaneously fits parameters with the whole A/C _c curve, mean V_cmax estimated from A/C _i curve analysis (V_cmax-C _i) was underestimated by 37.49%; mean Jmax estimated from A/C _i curve analysis (J_max-C _i) was overestimated by 17.8% and (J_max-C _i)/(V_cmax-C _i) was overestimated by 24.2%. However, there was a significant linear relationship between V_cmax estimated from A/C _i curve analysis and V_cmax estimated from A/C _c curve analysis, so was it J_max (p<0.05).     

Alkylation of isolated chromatin with N-methyl-N-nitrosourea and N-ethyl-N-nitrosourea

When isolated chromatin is incubated with the carcinogens N-methyl-N-nitrosourea (MeNU) and N-ethyl-N-nitrosourea (EtNU), DNA and chromosomal proteins become alkylated to increasingly greater extents as the carcinogen concentrations increase. With either MeNU or EtNU, the core and linker DNA of chromatin are alkylated to essentially identical extents. Alkylation of chromatin DNA as well as free DNA is drastically reduced at physiological ionic strengths (e.g. 0.15 M NaCl). The presence of 0.15 M NaCl, on the other hand, enhances alkylation of chromosomal proteins. While EtNU is much less reactive to DNA than MeNU, alkylation of chromosomal proteins relative to that of chromatin DNA has been found to be markedly greater with EtNU than with MeNU. Such a difference in their relative reactivities toward DNA and proteins may be related to the known difference of carcinogenic potency between these N-nitroso compounds.     

Comparative study of Bifidobacteriumanimalis, Escherichiacoli, Lactobacilluscasei and Saccharomycesboulardii probiotic properties

The present work investigates some probiotic properties of four different microorganisms (Bifidobacterium animalis var. lactis BB-12, Escherichia coli EMO, Lactobacillus casei and Saccharomyces boulardii). In vitro and in vivo tests were carried out to compare cell wall hydrophobicity, production of antagonistic substances, survival capacity in the gastrointestinal tract of germ-free mice without pathological consequence, and immune modulation by stimulation of Küpffer cells, intestinal sIgA and IL-10 levels. In vitro antagonism against pathogenic bacteria and yeast was only observed for the probiotic bacteria B. animalis and L. casei. The hydrophobic property of the cell wall was higher for B. animalis and E. coli EMO, and this property could be responsible for a better ability to colonize the gastrointestinal tract of germ-free mice. Higher levels of sIgA were observed mainly for S. boulardii, followed by E. coli EMO and B. animalis, and only S. boulardii induced a significant higher level of IL-10. In conclusion, for a probiotic use, S. boulardii presented better characteristics in terms of immunomodulation, and B. animalis and L. casei for antagonistic substance production. The knowledge of the different probiotic properties could be used to choice the better microorganism depending on the therapeutic or prophylactic application.     

Ribonucieic Acid and Protein Metabolism of t12/t12 Embryos and T/t12 Spermatozoa

RNA precursor uptake and incorporation, amino acid uptake and incorporation, and the characterization of newly synthesized RNA and protein in pools of normal morulae and pools containing one-third t ¹²/ t ¹² morulae were compared. Maturing spermatoza of +/+ and T / t ¹² animals were analyzed for RNA and protein content, and the RNA characterized. No differences in these parameters could be ascribed to the t ¹² gene in homozygous embryos or haploid sperm.     

百合LbCAT和LbGPX基因的克隆与表达分析

以切花百合(Lilium brownii var. viridulum)‘卡瓦纳’cDNA为模板,克隆了过氧化氢酶(LbCAT)和谷胱甘肽过氧化物酶(LbGPX)基因。序列分析表明,这2个基因分别包含1 479 bp和519 bp的开放阅读框(ORF),编码492个和172个氨基酸。进化分析结果表明,LbCAT蛋白与岷江百合CAT蛋白的氨基酸序列相似性最高(99.19%),且亲缘关系最近;LbGPX蛋白与油棕GPX蛋白的氨基酸序列相似性最高(78.61%),亲缘关系最近。qRT PCR结果显示,LbCAT和LbGPX在百合根、鳞茎、叶和花中都有表达。LbCAT在叶中表达量最高,LbGPX在花中表达量最高。这2个基因在百合花蕾的生长发育过程中均有表达,且表达量逐渐增加;在PEG处理后2个基因的转录水平升高,但独角金内酯(SLs)处理却显著降低了这2个基因的转录水平;该结果为百合抗逆性机理研究以及抗逆育种奠定了基础。     

C-Glycosylflavones and xanthones in leaves of Rigidella,sessilanthera and Fosteria

Four New World genera are included in the tribe tigrideae of the Iridaceae. These genera, which have been the subject of recent systematic treatments [1–4], share many characteristics; e.g. a haploid complement of two large and 12 small chromosomes and bisulcate pollen grains. However, the taxonomic and phyletic relationships within and between these genera have been based strictly on floral morphology and may simply reflect the primary pollinators of these genera [4,5].The flavonoid chemistry of eight species in three of the four genera, Rigidella, Sessilanthera and Fosteria, was investigated as part of a systematic study of Tigrideae. Our results are summarized in Table 1 nad Fig. 1. Although a recurrent pattern of $\text{C-}\text{glycosylflavones}$ and xanthones characterize the leaves of these taxa, each species exhibits a distinctive array of compounds. The same classes of compounds occur in other tribes of the Iridaceae: $\text{C-}\text{glycosylflavones}$ occur in the Irideae [6,7], Cipureae, and Mariceae and xanthones in Irideae [6] and Sisyrinchieae [6].     

Cloning and characterization of femA and femB from Staphylococcus epidermidis

A DNA fragment was identified and cloned from Staphylococcus epidermidis (Se) using femA from S. aureus (Sa) as a heterologous hybridization probe. DNA sequence analysis of a portion of this clone revealed two complete ORFs highly related to femA and femB of Sa. The genomic arrangement of the Se femA/B complex was nearly identical to that observed in Sa. Intra- and interspecies relatedness of these genes and conservation of genomic organization were consistent with gene duplication of one of these genes in an ancestral organism. Recombinant FEMA, produced in Escherichia coli (Ec), was purified to near homogeneity. Identity of the purified protein was verified by N-terminal amino acid (aa) sequence analysis.     

Natural abundance of 13C and 15N in C3 and C4 vegetation of southern Africa: patterns and implications

The mean annual rainfall in southern Africa is found to explain over half of the observed variance in the stable nitrogen (N) isotopic signatures of C₃ vegetation in southern Africa (r²=0.54, P<0.01). The inverse relationship between the stable N isotopic signatures of foliar samples from C₃ vegetation and long‐term southern African rainfall is found on a scale larger than previously observed. A modest relationship is found between stable carbon (C) isotopic signatures of C₃ vegetation and rainfall across the region (r²=0.20, P<0.01). No such relationship is found between stable C and N isotopic signatures of C₄ vegetation and rainfall. The explanation of the relationship between ¹⁵N in C₃ vegetation and the mean annual rainfall presented here is that nutrient availability varies inversely with water availability. This suggests that water‐limited systems in southern Africa are more open in terms of nutrient cycling and therefore the resulting natural abundance of foliar ¹⁵N in these systems is enriched. The use of this relationship may be of value to those researchers modeling both the dynamics of vegetation and biogeochemistry across this region. The use of the isotopic enrichment in C₃ vegetation as a function of rainfall may provide an insight into nutrient cycling across the semi‐arid and arid regions of southern Africa. This finding has implications for the study of global change, especially as it relates to vegetation responses to changing regional rainfall regimes over time.     

Effects of cadmium and lead on the accumulation of Ca2+ and K+ and on the influx and translocation of K+ in wheat of low and high K+ status

The effects of cadmium and lead on the internal concentrations of Ca²⁺ and K⁺, as well as on the uptake and translocation of K(⁸⁶Rb⁺) were studied in winter wheat (Triticum aestivum L. a. MV-8) grown hydroponically at 2 levels of K⁺ (100 uM and 10 mM). Cd²⁺ and Pb²⁺ were applied in the nutrient solution in the range of 0.3 to 1000 u.M. Growth was more severely inhibited by Cd²⁺ and in the high-K⁺ plants as compared to Pb^z+ and low-K⁺ plants. Ions of both heavy metals accumulated in the roots and shoots, but the K⁺ status influenced their levels. Ca²⁺ accumulation was increased by low concentrations of Cd²⁺ mainly in low-K⁺ shoots, whereas it was less influenced by Pb²⁺. The distribution of Cd²⁺ and Ca²⁺ in the plant and in the growth media indicated high selectivity for Cd²⁺ in the root uptake, while Ca²⁺ was preferred in the radial and/or xylem transport. Cd²⁺ strongly inhibited net K⁺ accumulation in high-K⁺ plants but caused stimulation at low K⁺ supply. In contrast, the metabolis-dependent influx of K⁺(⁸⁶Rb⁺) was inhibited in low-K⁺ plants, while the passive influx in high-K⁺ plants was stimulated. Translocation of K⁺ from the roots to the shoots was inhibited by Cd²⁺ but less influenced in Pb²⁺-treated plants. It is concluded that the effects of heavy metals depend upon the K⁺-status of the plants.     

A/California/7/2009与A/California/4/2009病毒感染力比较

目的甲型H1N1流感病毒A/California/7/2009与A/California/4/2009病毒序列比较同源性在99%以上,本实验旨在比较两株病毒感染BALB/c小鼠研究感染力强弱。方法分别将A/California/7/2009（CA7）与A/California/4/2009（CA4）两株病毒分别连续10倍稀释后,对4~6周龄雌性BALB/c小鼠经乙醚麻醉后进行滴鼻攻毒,每个稀释度接种10只实验小鼠,测定CA7 MLD50为101.24/0.05 mL,检测小鼠感染、致病的多项指标,观察期为14 d。结果相同TCID50的CA7和CA4病毒感染小鼠,CA4感染小鼠后14 d内死亡率为20%,而CA7感染小鼠后8 d内死亡率为100%。CA7 106TCID50感染的小鼠病理表现为重度弥漫性间质性肺炎,CA4 106TCID50感染的小鼠病理表现为中度-重度间质性肺炎。结论在相同条件下,CA7感染力明显强于CA4。     

The effect of the rcation/ranion ratio on the structural and chemical properties of N-chloroarenesulfonamidates

A comparative structural study on sodium and potassium N-chloroarenesulfonamidates has been carried out using X-ray diffraction and IR spectroscopy as experimental techniques. As shown by crystallographic studies, the sodium ions tend to incorporate more water oxygen atoms in their coordination spheres than the potassium ions, while the potassium congeners prefer the interaction with sulfonamidate moieties. The marked dissimilarity between the compositions of the coordination spheres as well as the different tendency of the sodium and potassium salts to absorb moisture from the air have been attributed to the different sizes of the sodium and potassium ions. The opposite shifts of the ν_as(SO₂) and ν(SN) bands upon dehydration have been ascribed to an increased polarization of the sulfonyl group by the metal centers. Based on IR spectroscopic observations, a weakening of the N-Cl bonds is suspected in the water-free compounds, which may contribute to the known thermal instability of the dehydrated salts of N-chloroarenesulfonamides. Various sections of IR spectra as well as X-ray powder diffraction patterns have proved to be suitable to identify the water-free and hydrated samples.     

A comparison of NH4+ and NO3– net fluxes along roots of rice and maize

Net fluxes of NH₄⁺ and NO₃^– along adventitious roots of rice ( Oryza sativa L.) and the primary seminal root of maize ( Zea mays L.) were investigated under nonperturbing conditions using ion-selective microelectrodes. The roots of rice contained a layer of sclerenchymatous fibres on the external side of the cortex, whereas this structure was absent in maize. Net uptake of NH₄⁺ was faster than that of NO₃^– at 1 mm behind the apex of both rice and maize roots when these ions were supplied together, each at 0·1 mol m^–3. In rice, NH₄⁺ net uptake declined in the more basal regions, whereas NO₃^– net uptake increased to a maximum at 21 mm behind the apex and then it also declined. Similar patterns of net uptake were observed when NH₄⁺ or NO₃^– was the sole nitrogen source, although the rates of NO₃^– net uptake were faster in the absence of NH₄⁺. In contrast to rice, rates of NH₄⁺ and NO₃^– net uptake in the more basal regions of maize roots were similar to those near the root apex. Hence, the layer of sclerenchymatous fibres may have limited ion absorption in the older regions of rice roots.     

苜蓿中华根瘤菌fabA和fabB基因功能的鉴定

在大肠杆菌(Escherichia coli)脂肪酸合成酶体系中,fabA基因编码有双功能的3-羟基脂酰ACP脱水异构酶,其异构产物能被fabB基因编码的3-酮基脂酰ACP合成酶Ⅰ延伸,合成不饱和脂肪酸,该FabA-FabB途径被认为是缺氧条件下不饱和脂肪酸合成的经典途径．生物信息学分析发现,苜蓿中华根瘤菌(Sinorhizobium meliloti)的SmFabA与EcFabA相似性达到60.6%,具有相同的保守活性位点和两个保守的α螺旋结构;SmFabB与EcFabB相似性达到61.1%,具有相同的Cys-His-His活性中心．用携带SmfabA和SmfabB的质粒载体遗传互补大肠杆菌温度敏感突变株CY57和CY242,在添加三氯森(TCL)抑制烯脂酰ACP还原酶活性的条件下,转化子能在42℃恢复生长,且放射性薄层层析能检测到转化子中不饱和脂肪酸棕榈油酸(Δ9C16:1)和十八碳烯酸(Δ11C18:1)的合成．体外重建脂肪酸合成反应表明,SmFabA能催化羟脂酰ACP的脱水反应且能够使反-2-癸烯酰ACP异构化,SmFabB能催化不同链长的脂酰ACP和丙二酸单酰ACP的聚合反应．另外,未得到SmFabA和SmFabB的突变株,表明SmFabA和SmFabB可能是苜蓿中华根瘤菌脂肪酸合成酶系中必不可少的关键蛋白．上述结果证实了苜蓿中华根瘤菌fabA和fabB两个基因在不饱和脂肪酸合成中的功能．     

The sequence of RNA segment 1 of influenza virus A/NT/60/68 and its comparison with the corresponding segment of strains A/PR/8/34 and A/WSN/33.

The complete nucleotide sequence of RNA segment 1 of influenza virus A/NT/60/68, corresponding to the PB2 protein, has been determined. It is 2341 nucleotides long, encoding a predicted product of 759 amino acids with a net charge of +27 1/2 at neutral pH. The predicted amino acid sequence has been compared to the equivalent sequences in influenza viruses A/PR/8/34 and A/WSN/33. Evolutionary divergence, assuming a direct lineage from A/PR/8/34 and allowing for "laboratory drift", is 0.08% per year. The alignment of RNA segment 10 of A/NT/60/68 with segments 1 and 3 is completed, confirming that it is a mosaic of regions from these two segments.     

Synthesis and molecular structure of the all-trans- and the trans-cis-isomers of dichlorodimethyltin complexes of phosphoric triamides

Four new phosphoramidates with formula 4-RC₆H₄C(O)NHP(O)(NH(CH(CH₃)₂)₂, R = H (1), OCH₃ (2), CH₃ (3), Cl (4) and their diorganotin(IV) complexes with formula SnCl₂(CH₃)₂(X)₂, X = 1 (5), 2 (6), 3 (7) and 4 (8) were synthesized and characterized by NMR, IR spectroscopy and elemental analysis. The spectroscopic properties of complexes were compared with those corresponding ligands. The molecular structures for 5, 5·CH₃CN, 6·CH₃CN, 7 and 8 were established by X-ray diffraction analysis and shown that the tin atoms have a distorted octahedral coordination with trans-methyl groups. Two different all-trans and cis-trans isomers were obtained by changing the crystallization solvent system. The existence of CH₃CN in molecular packing of trans-cis isomers might be a packing factor governing the orientation of the ligands. Due to the presence of several hydrogen bond donors and acceptors on compounds, extended hydrogen-bonded networks were observed. The structure of 2 was also determined and possesses two crystallographically independent molecules in asymmetric unit. On forming complex 6·CH₃CN, the ligand 2 shows shortening of CO and P-N bond distances and increasing of PO bond length. Pseudopolymorphism of diorganotins in 5 and 5·CH₃CN is reported for the first time.     

Syn-anti and anti-anti conformations of a diimine derived from p-xylylenediamine and its neutral Co and Zn dinuclear complexes

A symmetric diimine ligand containing a CH₂PhCH₂ bridging group (H₂XyTs: N,N′-bis(2-tosylaminobenzylidene)-1,4-xylylenediamine) and its neutral Co^II and Zn^II dinuclear complexes have been prepared. Two different crystal structures of the free ligand, H₂XyTs, and that corresponding to [Co₂(XyTs)₂], have been solved by X-ray diffraction methods. These revealed two different conformations (syn-anti and anti-anti) for H₂XyTs and an infrequent rotational isomerism on the xylylene rings of its Co^II dinuclear complex, where both ligands are syn-anti conformed. Characterisation of the compounds is completed with FT-IR, ESI-MS and ¹H NMR spectroscopic techniques, when possible.