Oxidative processes at initial stages of interaction of nodule bacteria (<Emphasis Type="Italic">Rhizobium leguminosarum</Emphasis>) and pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.): A review

A possible physiological mechanism of legume-Rhizobium symbiosis, consisting in regulation of the intensity of oxidative processes by the macrosymbiont in response to infection with Rhizobium, was analyzed using our own and published data. The results used in the analysis included data on the content of reactive oxygen species (O ₂ ^·? and H₂O₂), activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase), and intensity of lipid peroxidation proceeding with the involvement of lipophilic phenolic compounds of the microsymbiont.     

Structural characterization of extracellular polysaccharides of Azorhizobium caulinodans and importance for nodule initiation on Sesbania rostrata

During lateral root base nodulation, the microsymbiont Azorhizobium caulinodans enters its host plant, Sesbania rostrata, via the formation of outer cortical infection pockets, a process that is characterized by a massive production of H(2)O(2). Infection threads guide bacteria from infection pockets towards nodule primordia. Previously, two mutants were constructed that produce lipopolysaccharides (LPSs) similar to one another but different from the wild-type LPS, and that are affected in extracellular polysaccharide (EPS) production. Mutant ORS571-X15 was blocked at the infection pocket stage and unable to produce EPS. The other mutant, ORS571-oac2, was impaired in the release from infection threads and was surrounded by a thin layer of EPS in comparison to the wild-type strain that produced massive amounts of EPS. Structural characterization revealed that EPS purified from cultured and nodule bacteria was a linear homopolysaccharide of alpha-1,3-linked 4,6-O-(1-carboxyethylidene)-D-galactosyl residues. In situ H(2)O(2) localization demonstrated that increased EPS production during early stages of invasion prevented the incorporation of H(2)O(2) inside the bacteria, suggesting a role for EPS in protecting the microsymbiont against H(2)O(2). In addition, ex planta assays confirmed a positive correlation between increased EPS production and enhanced protection against H(2)O(2).     

Complete genome sequence of the Medicago microsymbiont Ensifer (Sinorhizobium) medicae strain WSM419

Ensifer (Sinorhizobium) medicae is an effective nitrogen fixing microsymbiont of a diverse range of annual Medicago (medic) species. Strain WSM419 is an aerobic, motile, non-spore forming, Gram-negative rod isolated from a M. murex root nodule collected in Sardinia, Italy in 1981. WSM419 was manufactured commercially in Australia as an inoculant for annual medics during 1985 to 1993 due to its nitrogen fixation, saprophytic competence and acid tolerance properties. Here we describe the basic features of this organism, together with the complete genome sequence, and annotation. This is the first report of a complete genome sequence for a microsymbiont of the group of annual medic species adapted to acid soils. We reveal that its genome size is 6,817,576 bp encoding 6,518 protein-coding genes and 81 RNA only encoding genes. The genome contains a chromosome of size 3,781,904 bp and 3 plasmids of size 1,570,951 bp, 1,245,408 bp and 219,313 bp. The smallest plasmid is a feature unique to this medic microsymbiont.     

Uniformity of the microsymbiont population from soybean nodules with respect to buoyant density

The microsymbiont population in soybean root nodules (Glycine max L. cv Williams 82 inoculated with Bradyrhizobium japonicum 2143) was characterized during symbiotic development to determine the extent of heterogeneity in this population. The microsymbiont population was isolated by centrifugation through a continuous sucrose gradient (44 to 57% weight to weight ratio) and appeared homogeneous at each age examined up to 26 days after planting based on the symmetrical distribution of the population, enzyme activities, poly-β-hydroxybutyrate contents, protein contents, and viabilities. Some differences in viability, protein content, and acetylene reduction activity were observed at later ages. The population migrated to progressively lighter buoyant densities with increasing age until a density equivalent to 48% sucrose was reached. The changing density correlated directly with the increasing poly-β-hydroxybutyrate to protein ratio. The acetylene reduction activity, based on microsymbiont concentration, followed the same developmental pattern as whole nodules. On a protein basis, the decline of acetylene reduction activity was later and reflected the decrease in protein content per cell. These results suggested that the microsymbiont population, which resulted from inoculation of B. japonicum 2143 onto Williams 82 cultivar of soybeans, developed as a homogeneous population.     

Ultrastructure of infected cells in the actinorhizal root nodules ofGymnostoma papuanum (Casuarinaceae) prepared by high pressure freezing and chemical fixation

Summary Actinorhizal root nodules ofGymnostoma papuanuum (Casuarinaceae) were examined with transmission electron microscopy after being either fixed with glutalaldehyde and osmium tetroxide or frozen with liquid nitrogen at high pressure and freeze-substituted. Much better preservation was obtained by the cryopreservation method. Mitochondria, plastids, membranes und ribosomes were much better preserved in the frozen specimens than in the chemically fixed tissues. No nucleoids were observed in the microsymbiont in frozen specimens. In contrast nucleoid regions were present in chemically fixed specimens. The actinomycete microsymbiont differentiates small spherical-shaped symbiotic vesicles after the hyphae have grown and penetrated into most regions of the cytoplasm.Dedicated to the memory of Professor Oswald Kiermayer     

Structural chemistry of actinide compounds with different coordination numbers: The crystal and molecular structures of tetrachlorotris(N,N-diethylpropionamide)thorium(IV) and tetra-N-thiocyanato tetrakis(N,N-dimethylpropionamide)thorium(IV)

The crystal and molecular structures of ThCl₄(depa)₃ (1) (depa = N,N-diethylpropionamide) and Th(NCS)₄(dmpa)₄ (2) (dmpa = N,N-dimethylpropionamide) have been determined from three-dimensional X-ray diffraction data. The compounds crystallize in space group P2₁/n (1) and P2₁/a (2), with a = 18.107(5), b = 10.347(3), c = 17.867(5) Å, β = 108.5(1)°, Z = 4 (1) and a = 22.759(6), b = 13.763(4), c = 11.910(3) Å, β = 91.4(1)° and Z = 4 (2). Full matrix least-squares refinement of both structures gave for (1) with 3126 intensity data R = 0.046 and Rw 0.046 and for (2) with 3480 intensity data R = 0.050, Rw 0.054. The different steric constraints imposed by the ligand give rise to different coordination numbers. In (1) the coordination polyhedron about the seven co-ordinate thorium atom is a pentagonal bipyramid with two chlorine atoms in the axial positions, an unusual geometry for Th(IV) species. The average bonding distances are ThO = 2.340(9), ThCl_eq = 2.754(3) and ThCl_ax = 2.692(3) Å.In (2) the less hindering dmpa ligand favours the presence of four of them in the metal coordination sphere in a distorted square antiprismatic coordination geometry. ThO and ThN average 2.37(1) and 2.49(2) Å respectively.     

In vivo singlet-oxygen generation in blood of chromium(VI)-treated mice

Although it is assumed from in vitro experiments that the generation of reactive oxygen species such as the singlet oxygen (1O2), the hydroxyl radical, and the superoxide anion are responsible for chromium(VI) toxicity/carcinogenicity, no electron spin resonance (ESR) evidence for the generation of 1O2 in vivo has been reported. In this study, we have employed an ESR spin-trapping technique with 2,2,6,6-tetramethyl-4-piperidone (TMPD), a specific 1O2 trap, to detect 1O2 in blood. The ESR spectrum of the spin adduct observed in the blood of mice given 4.8 mmol Cr(VI)/kg body weight exhibited the 1:1:1 intensity pattern of three lines with a hyperfine coupling constant A(N) = 16.08 G and a g-value = 2.0066. The concentration of spin adduct detected in the blood was 1.46 microM (0.1% of total Cr concentration). The adduct production was inhibited by the addition of specific 1O2 scavengers such as 1,4-diazabicyclo[2.2.2]octane and sodium azide to the blood. The results indicate that the spin adduct is nitroxide produced by the reaction of 1O2 with TMPD. This is the first report of ESR evidence for the in vivo generation of 1O2 in mammals by Cr(VI).     

Truncated hemoglobins in actinorhizal nodules of Datisca glomerata

Three types of hemoglobins exist in higher plants, symbiotic, non-symbiotic, and truncated hemoglobins. Symbiotic (class II) hemoglobins play a role in oxygen supply to intracellular nitrogen-fixing symbionts in legume root nodules, and in one case ( Parasponia Sp.), a non-symbiotic (class I) hemoglobin has been recruited for this function. Here we report the induction of a host gene, dgtrHB1, encoding a truncated hemoglobin in Frankia-induced nodules of the actinorhizal plant Datisca glomerata. Induction takes place specifically in cells infected by the microsymbiont, prior to the onset of bacterial nitrogen fixation. A bacterial gene (Frankia trHBO) encoding a truncated hemoglobin with O (2)-binding kinetics suitable for the facilitation of O (2) diffusion ( ) is also expressed in symbiosis. Nodule oximetry confirms the presence of a molecule that binds oxygen reversibly in D. glomerata nodules, but indicates a low overall hemoglobin concentration suggesting a local function. Frankia trHbO is likely to be responsible for this activity. The function of the D. glomerata truncated hemoglobin is unknown; a possible role in nitric oxide detoxification is suggested.     

Genetic Diversity of Frankia Microsymbionts in Root Nodules from Colletia hystrix (Clos.) Plants by Sampling at a Small-Scale

Summary The genetic diversity of microsymbiont Frankia from Colletia hystrix (Clos.) plants growing in a restricted area, were investigated by PCR-restriction fragment length polymorphism (RFLP) technique. DNA from field-collected nodules was amplified by PCR with primers targeting two genomic regions; one included a large portion of the 3′ end of the 16S rRNA gene, the intergenic spacer, and the 5′ end of the 23S rRNA gene and the other in the nifD–nifK intergenic region in the nif operon as a means to estimate molecular diversity. A HaeIII digestion of the PCR product allowed us to identify PCR-RFLP groups or haplotypes among the Colletia-infective Frankia strains tested. An exhaustive small-scale sampling permitted us to detect haplotypes with a low frequency in the microsymbiont population and showed that Frankia microsymbionts have a higher genetic diversity than previously reported. Fifteen haplotypes were recognized on the basis of combining the restriction patterns in each region analyzed. The haplotype designated as A3 was found with a high frequency in the five microsymbiont Frankia groups studied indicating a dominant haplotype. This haplotype was also exhibited by strain ChI4, which was isolated in 1991 in the same locality suggesting that it is the most common haplotype in this area and very stable over time.     

P(M) and P(R) forms of cytochrome c oxidase have different spectral properties

This work presents the study of the interaction between zidovudine (AZT) and rare earth (RE) ions with thenoyltrifluoroacetonate (TTA). The complexes [RE(TTA)(3) x (AZT)(2)] (where RE(III)=Eu and Gd) were prepared by reaction between the [RE(TTA)(3) x (H(2)O)(2)] precursors and AZT dissolved in acetone in the molar ratio 1:2. The obtained luminescent materials were characterized by microanalyses (C, H, N), complexometric titration, IR spectroscopy, X-ray powder diffraction and thermal analysis (DSC and TG/DTG). The luminescence data indicate that the substitution of the two water molecules by AZT in the europium complex causes an intensification of luminescence corresponding to the (5)D(0) -->(7)F(J) (J=0-4) transitions associated with one of the site symmetries. Based on the luminescence spectrum of the Eu(III)-compound the Omega(lambda) experimental intensity parameters (lambda=2 and 4) were calculated for the electronic transitions (5)D(0)-->(7)F(2, 4). The Omega(2) intensity parameter for this new compound is higher than for the precursor compound, suggesting an effective interaction between the AZT and the chemical environment of the Eu(III) ion. Luminescence data confirm that the AZT complex and precursor compound have a comparable emission quantum efficiency.     

中华青荚叶的一个新果糖酯

从山茱萸科中华青荚叶( Helwingia chinensis )的乙醇提取物中分离得到一个新果糖酯和十个已知化合物.通过现代波谱技术分别鉴定为:2- O -(E)-咖啡酰-3- O -(3, 5-二甲氧基香豆酰)-α-D-呋喃果糖甙(1),2- O -β-D-呋喃果糖基α-D-异吡喃糖酯(2),甘草甜素(3),4′-羟基-7- O -葡萄糖-2, 3-二羟黄酮甙(4),黄豆甙(5),5-葡萄糖芹菜甙(6),7- O -葡萄糖芹菜甙(7),4- O -葡萄糖香豆酸(8), 葡萄糖咖啡酸(9), 3β-赤杨醇(10), 薯蓣皂甙3- O -{α-L-鼠李糖吡喃糖基(1→2)-[α-L-阿拉伯呋喃糖基(1→3)]-β-D-葡萄糖吡喃糖} (11).     

Parasitic helminths of Eurasian collared-doves (Streptopelia decaocto) from Florida

Sixty-three Eurasian collared-doves (ECDs) (Streptopelia decaocto) from Florida were examined for parasitic helminths from June to December 2001. Nine species of helminths were identified (5 nematodes, 2 cestodes, and 2 trematodes). The most prevalent helminths were Ascaridia columbae (73.0%), Fuhrmannetta crassula (28.6%), Ornithostrongylus quadriradiatus (12.7%), and Bruscapillaria obsignata (11.1%). The helminths with the greatest mean intensity were Tanaisia bragai (13.5), A. columbae (9.3), and O. quadriradiatus (7.1). In Florida, the mean intensity of A. columbae in ECDs (9.3) was similar to that found in white-winged doves (Zenaida asiatica) (9.1) (P = 0.461), and both the intensities were significantly higher than that in the native mourning doves (Zenaida macroura) (3.7) (P = 0.001 and 0.005, respectively). Fuhrmannetta crassula is reported for the first time in columbids from Florida.     

Study on mammal (rat) of the neuro-muscular synapse function under hyperbaric conditions (11 ata): effects of the curarization

Under hyperbaric conditions (11 ata) obtained with normoxic O2-N2 mixtures spontaneous EMG activity disappears, as do reactions to noise, but this phenomenon is reversible after the substitution of Helium for Nitrogen in the mixture. Analysis of EMG responses to sciatic nerve excitation has revealed no difference between the EMG tracings recorded under normobaric pressure and those obtained under hyperbaric conditions (O2-N2 or O2-He, 11 ata), and hyperbaric conditions do not seem to interfere with neuro-muscular synaptic transmission. Furthermore, the effect of Pavulon (an antidepolarising, acetyl-cholino-competitive curare-mimetic drug) is similar under normal and hyperbaric conditions: hyperbaria change neither the onset of neuro-muscular blockage nor its intensity or duration. The absence of a specific effect on synapse function of a change in the diluting gas from nitrogen to helium suggests that there was no change in post-synaptic receptor function. This result is not in accordance with the hypothesis that inert gas pressures of less than 10 ata modify molecular structures particularly at the neuro-muscular synapse level.     

Complete genome sequence of Rhizobium leguminosarum bv trifolii strain WSM2304, an effective microsymbiont of the South American clover Trifolium polymorphum

Rhizobium leguminosarum bv trifolii is the effective nitrogen fixing microsymbiont of a diverse range of annual and perennial Trifolium (clover) species. Strain WSM2304 is an aerobic, motile, non-spore forming, Gram-negative rod, isolated from Trifolium polymorphum in Uruguay in 1998. This microsymbiont predominated in the perennial grasslands of Glencoe Research Station, in Uruguay, to competitively nodulate its host, and fix atmospheric nitrogen. Here we describe the basic features of WSM2304, together with the complete genome sequence, and annotation. This is the first completed genome sequence for a nitrogen fixing microsymbiont of a clover species from the American center of origin. We reveal that its genome size is 6,872,702 bp encoding 6,643 protein-coding genes and 62 RNA only encoding genes. This multipartite genome was found to contain 5 distinct replicons; a chromosome of size 4,537,948 bp and four circular plasmids of size 1,266,105 bp, 501,946 bp, 308,747 bp and 257,956 bp.     

The role of the system of superoxide radical formation and detoxication in the mechanism of the antineoplastic effect of adriamycin

The intensity of formation of superoxide radicals (O(-2)) and superoxide dismutase (SOD) activity in the tissue of two transplantable gliomas were examined. The cells of these tumors were marked by unbalance between the intensity of O(-2) formation by nuclear membranes and their detoxication of SOD. This unbalance was particularly demonstrable in glioma 35 which was marked by rapid growth and high sensitivity to adriamycin. Slow-growing glioma was noted for higher activity of SOD and was insensitive to adriamycin. Since it is known that anthracycline antibiotics raise the intensity of the formation of free oxygen radicals in tumor cells, the data obtained suggest that the intensity of formation and detoxication of O(-2) may be used for the assessment of the sensitivity to these drugs.     

The interaction of 5-fluoroorotic acid with transition metals: synthesis and characterisation of Ni(II), Cu(II) and Zn(II) complexes

5-Fluoroorotic acid (H(3)FOro) is a potent inhibitor for some metalloproteins such as dihydroorotase and dihydroorotate dehydrogenase and for thymidylate synthase (nonmetalloprotein) in the human malaria parasite Plasmodium falciparum. To study the coordination chemistry of H(3)Foro, the ammonium salt [NH(4)(+)][H(2)FOro(-)].1H(2)O (1) and the first coordination compounds of H(3)FOro with transition metals [Ni(HFOro(2-))(H(2)O)(4)].1H(2)O (2), [Cu(HFOro(2-))(NH(3))(H(2)O)](n) (3) and [Cu(3)(FOro(3-))(2)(NH(3))(6)(H(2)O)(2)] (4) have been synthesised and characterised by single-crystal X-ray diffraction, IR spectroscopy and by thermogravimetry. Three different coordination modes of 5-fluoroorotic acid have been established. In all cases the ligand is chelated to the metal via an amido-nitrogen and a carboxylate-oxygen but for (3), there is also a carboxylate oxygen from another HFOro(2-) ligand resulting in a polymeric structure and for (4), the second amido-nitrogen in the ororotic acid ring coordinates to give a trinuclear complex. The metal coordination polyhedra are octahedral in (2), square-pyramidal in (3) and square-planar and approximately square-pyramidal in (4). An octahedral coordination geometry including a N(1)/O(61)-chelating HFOro(2-) ligand with four aqua ligands is proposed for the Zn complex [Zn(HFOro(2-)) (H(2)O)(4)].0.5H(2)O (5), based on IR and thermogravimetric data. Extensive hydrogen bonded networks and some ring-ring stacking interactions are observed in each of the structures.     

Co-evolution between Frankia populations and host plants in the family Casuarinaceae and consequent patterns of global dispersal

Symbioses between the root nodule-forming, nitrogen-fixing actinomycete Frankia and its angiospermous host plants are important in the nitrogen economies of numerous terrestrial ecosystems. Molecular characterization of Frankia strains using polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) analyses of the 16S rRNA-ITS gene and of the nifD-nifK spacer was conducted directly on root nodules collected worldwide from Casuarina and Allocasuarina trees. In their native habitats in Australia, host species contained seven distinctive sets of Frankia in seven different molecular phylogenetic groups. Where Casuarina and Allocasuarina trees are newly planted outside Australia, they do not normally nodulate unless Frankia is introduced with the host seedling. Nodules from Casuarina trees introduced outside Australia over the last two centuries were found to contain Frankia from only one of the seven phylogenetic groups associated with the host genus Casuarina in Australia. The phylogenetic group of Frankia found in Casuarina and Allocasuarina trees introduced outside Australia is the only group that has yielded isolates in pure culture, suggesting a greater ability to survive independently of a host. Furthermore, the Frankia species in this group are able to nodulate a wider range of host species than those in the other six groups. In baiting studies, Casuarina spp. are compatible with more Frankia microsymbiont groups than Allocasuarina host spp. adapted to drier soil conditions, and C. equisetifolia has broader microsymbiont compatibility than other Casuarina spp. Some Frankia associated with the nodular rhizosphere and rhizoplan, but not with the nodular tissue, of Australian hosts were able to nodulate cosmopolitan Myrica plants that have broad microsymbiont compatibility and, hence, are a potential host of Casuarinaceae-infective Frankia outside the hosts' native range. The results are consistent with the idea that Frankia symbiotic promiscuity and ease of isolation on organic substrates, suggesting saprophytic potential, are associated with increased microsymbiont ability to disperse and adapt to diverse new environments, and that both genetics and environment determine a host's nodular microsymbiont.     

Characteristics of natural infections of the stomach worm, Obeliscoides cuniculi (Graybill), in lagomorphs and woodchucks in Canada

Wild lagomorphs and woodchucks collected predominantly in southern Ontario, Canada were examined for subspecies of Obeliscoides cuniculi (Graybill). Obeliscoides cuniculi multistriatus was found in snowshoe hares (Lepus americanus). Obeliscoides cuniculi cuniculi was found in cottontail rabbits (Sylvilagus floridanus), European hares (Lepus capensis) and woodchucks (Marmota monax). Prevalence of Obeliscoides cuniculi multistriatus in snowshoe hares was 100% and mean intensity (and range of intensity) was 760 (9-4, 198) in Lindsay, Ontario in 1980. Mean intensity in hares varied trimonthly. The highest mean intensity of worms occurred in spring when most worms were adult. Transmission occurred mainly in spring. Most worms present in fall (70%) and winter (54%) were fourth stage. Immature fifth-stage and gravid females were present in hares during fall and winter. Prevalence and mean intensity of O. c. cuniculi in cottontails was 15% and 29 (1-118). Prevalence and mean intensity of O. c. cuniculi in woodchucks was 6% and 56 (16-118). European hares were infected with O. c. cuniculi, prevalence was 10% and mean intensity was 60 (36-83). In Ontario woodchucks and European hares were common in areas frequented by cottontail rabbits and probably acquired sporadic infections of O. c. cuniculi from infected cottontails.     

Impact of Grazing Intensity and Seasons on Greenhouse Gas Emissions in Tropical Grassland

Greenhouse gases (GHG) can be affected by grazing intensity, soil, and climate variables. This study aimed at assessing GHG emissions from a tropical pasture of Brazil to evaluate (i) how the grazing intensity affects the magnitude of GHG emissions; (ii) how season influences GHG production and consumption; and (iii) what are the key driving variables associated with GHG emissions. We measured under field conditions, during two years in a palisade-grass pasture managed with 3 grazing intensities: heavy (15 cm height), moderate (25 cm height), and light (35 cm height) N₂O, CH₄ and CO₂ fluxes using static closed chambers and chromatographic quantification. The greater emissions occurred in the summer and the lower in the winter. N₂O, CH₄, and CO₂ fluxes varied according to the season and were correlated with pasture grazing intensity, temperature, precipitation, % WFPS (water-filled pores space), and soil inorganic N. The explanatory variables differ according to the gas and season. Grazing intensity had a negative linear effect on annual cumulative N₂O emissions and a positive linear effect on annual cumulative CO₂ emissions. Grazing intensity, season, and year affected N₂O, CH₄, and CO₂ emissions. Tropical grassland can be a large sink of N₂O and CH₄. GHG emissions were explained for different key driving variables according to the season.