子宫异常出血与细菌L型感染的关系

通常认为,子宫异常出血由内分泌紊乱、内膜肿瘤和子宫内膜炎引起。通过对471例子宫异常出血内膜组织的细菌学及免疫组化等研究,我们发现绝大多数(85.7％)出血者原因不明,其中376例子宫内膜查见L型菌。本组细菌L型感染率为93.8％。提示子宫异常出血(包括绝经后出血)与细菌L型感染关系也很密切。并认为,子宫内膜细菌L型感染是导致子宫异常出血的重要原因之一。选择作用于细菌胞膜的药物治疗细菌L型感染效果最好。     

慢性扁桃体炎与细菌L型感染

通常认为,慢性扁桃体炎主要致病菌是金黄色葡萄球菌和乙型溶血性链球菌。通过50例慢性扁桃体炎的病原微生物培养、组织切片细菌学及电镜等研究,发现慢性扁桃体炎组织中细菌L型也相当常见,L型培养阳性率是88.5％,且组织切片L型感染率与培养阳性率基本一致(P>0.05)。电镜在扁桃体组织间质及上皮细胞、淋巴细胞等多种细胞内均见到细菌L型。提示慢性扁桃体炎与细菌L型感染关系极为密切。并认为,L型侵入组织并在宿主细胞内生长的特性,可能是慢性扁桃体炎反复发作、迁延不愈的重要原因。     

Biological nitrogen fixation for sustainable agriculture: A perspective

The economic and environmental costs of the heavy use of chemical N fertilizers in agriculture are a global concern. Sustainability considerations mandate that alternatives to N fertilizers must be urgently sought. Biological nitrogen fixation (BNF), a microbiological process which converts atmospheric nitrogen into a plant-usable form, offers this alternative. Nitrogen-fixing systems offer an economically attractive and ecologically sound means of reducing external inputs and improving internal resources. Symbiotic systems such as that of legumes and Rhizobium can be a major source of N in most cropping systems and that of Azolla and Anabaena can be of particular value to flooded rice crop. Nitrogen fixation by associative and free-living microorganisms can also be important. However, scientific and socio-cultural constraints limit the utilization of BNF systems in agriculture. While several environmental factors that affect BNF have been studied, uncertainties still remain on how organisms respond to a given situation. In the case of legumes, ecological models that predict the likelihood and the magnitude of response to rhizobial inoculation are now becoming available. Molecular biology has made it possible to introduce choice attributes into nitrogen-fixing organisms but limited knowledge on how they interact with the environment makes it difficult to tailor organisms to order. The difficulty in detecting introduced organisms in the field is still a major obstacle to assessing the success or failure of inoculation. Production-level problems and socio-cultural factors also limit the integration of BNF systems into actual farming situations. Maximum benefit can be realized only through analysis and resolution of major constraints to BNF performance in the field and adoption and use of the technology by farmers.     

Below-ground carbon distribution in barley (Hordeum vulgare L.) with and without nitrogen fertilization

The distribution of net assimilated C in barley (Hordeum vulgare L.) grown at two N-levels was determined in a growth chamber. The N-fertilization involved 0 and 3.61 mol N g^-1 dry soil. After growth for seven weeks in an atmosphere with continuously ¹⁴C-labelled CO₂, ¹⁴C was determined in shoots, roots, rhizosphere respiration and soil. At the low N-level, 32% of the net assimilated ¹⁴C was translocated below ground, whereas at the high N-level 27% was translocated below ground. The release of C from roots (root respiration, microbial respiration originating from decomposition of ¹⁴C-labelled root material and ¹⁴C remaining in soil) was greater with no N-supply (19% of net assimilated ¹⁴C) than in the treatment with N-supply (15%). Thus, the effect of N-supply on both translocation of assimilated ¹⁴C below ground and the release of ¹⁴C from growing roots was relatively small.     

Macromolecules Involved in the Amoeba-Bacteria Symbiosis1

ABSTRACT. In the Amoeba-bacteria symbiosis, rod-shaped Gram-negative bacterial endosymbionts reside within symbiosomes in the host cytoplasm, and the host and symbionts are mutually dependent for survival. Three proteins and one group of lipopolysaccharides (LPS) synthesized by the bacterial endosymbionts and two proteins derived from the host cells have been found to be involved in the host-symbiont interactions, although their respective roles are not yet fully known. The symbiont-derived molecules included proteins with molecular weights of 29 kDa, 67 kDa and 96 kDa and LPS. The 29-kDa protein was most abundant in the host cytoplasm, while the 96-kDa protein and LPS were found mostly on the symbiosome membranes. The 67-kDa protein was a GroEL analog and stayed within the symbionts. The host-derived 43-kDa protein, actin, was selectively accumulated by the symbionts, while the 220/225-kDa protein, spectrin, was attached to the symbiosome membranes. The symbiont genes coding for the 29-kDa and 67-kDa proteins were cloned and sequenced. The 29-kDa protein gene was unique with no relation to any known DNA sequences but has a leucine zipper-like motif, suggesting a possible DNA-binding function. The DNA sequence of the 67-kDa protein gene showed a 70% identity with heat-shock-protein genes of Escherichia coli and Coxiella burnetii.     

Effects of pantolactone and butyrolaectone on the pleiotropic phenotypes of lon mutants and on thermal induction of the SOS phenomena in a tif mutant of Escherichia coli K12

Hydrophobic and charge-charge interactions of Salmonella typhimirium and Serratia marcescens were determined and related to their content of fimbriae and lipopolysaccharide (LPS). The cell surface structures were characterized with hydrophobic interaction chromatography (HIC), electrostatic interaction chromatography (ESIC) and particle electrophoresis measurements. The degree of interaction at the air-water interface was tested using a monolayered lipid film applied to an aqueous surface. The cell surface hydrophobicity of S. typhimurium in the presence of fimbriae was less in smooth than in rought bacteria. Examination of a series of rough mutants of S. typhimurium indicates that reduction of the O-side chain and core oligosaccharides was correlated with increased cell hydrophobicity. The enrichment factors at the air-water interface were significantly higher for fimbriated than for non-fimbriated S. typhimurium cells. Fimbriated S. marcescens cells were less hydrophobic and adhered to a lesser degree at the air-water surface than non-fimbriated counterparts. Electrophoretic measurements and adsorption to ion exchangers gives different information about the surface charge of bacteria. The latter technique gives the interaction between localized charged surfaces.Abbreviations HIC hydrophobic interaction chromatography - ESIC electrostatic interaction chromatography - LPS lipopolysaccharide - PBS phosphate buffered saline solution     

On the precision and accuracy achieved by Escherichia coli cells at fission about their middle

Length and width of each of the prospective siblings of constricted Escherichia coli cells from different strains and culture conditions were measured from electron micrographs. The data were statistically analyzed to investigate how equally the length and volume of one cell was divided into two. The analysis showed that, for all cultures, bipartition is unbiased or very nearly so, i.e. sibling cells were on the average equally long and large. The precision of bipartition attained by the cells was usually high; it was related to the average cell shape (length/width): slender E. coli cells divided into two less precisely than squat cells. Absolute size, growth rate and strain specificity affected the precision of bipartition only indirectly, i.e. in as much as they influenced cell shape.     

On the mechanism of photosynthetic electron transfer in Rhodopseudomonas capsulata and Rhodopseudomonas sphaeroides

(1) Current models for the mechanism of cyclic electron transport in Rhodopseudomonas sphaeroides and Rhodopseudomonas capsulata have been investigated by observing the kinetics of electron transport in the presence of inhibitors, or in photosynthetically incompetent mutant strains. (2) In addition to its well-characterized effect on the Rieske-type iron sulfur center, 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole (UHDBT) inhibits both cytochrome b₅₀ and cytochrome b_?90 reduction induced by flash excitation in Rps. sphaeroides and Rps. capsulata. The concentration dependency of the inhibition in the presence of antimycin (approx. 2.7 mol UHDBT/mol reaction center for 50% inhibition of extent) is very similar to that of its inhibition of the antimycin-insensitive phase of ferricytochrome c re-reduction. UHDBT did not inhibit electron transfer between the reduced primary acceptor ubiquinone (Q^?_I) and the secondary acceptor ubiquinone (Q_II) of the reaction center acceptor complex. A mutant of Rps. capsulata, strain R126, lacked both the UHDBT and antimycin-sensitive phases of cytochrome c re-reduction, and ferricytochrome b₅₀ reduction on flash excitation. (3) In the presence of antimycin, the initial rate of cytochrome b₅₀ reduction increased about 10-fold as the E_h(7.0) was lowered below 180 mV. A plot of the rate at the fastest point in each trace against redox potential resembles the Nernst plot for a two-electron carrier with E_m(7.0) ≈ 125 ± 15 mV. Following flash excitation there was a lag of 100–500 μs before cytochrome b₅₀ reduction began. However, there was a considerably longer lag before significant reduction of cytochrome c by the antimycin-sensitive pathway occurred. (4) The herbicide ametryne inhibited electron transfer between Q^?_I and Q_II. It was an effective inhibitor of cytochrome b₅₀ photoreduction at E_h(7.0) 390 mV, but not at E_h(7.0) 100 mV. At the latter E_h, low concentrations of ametryne inhibited turnover after one flash in only half of the photochemical reaction centers. By analogy with the response to o-phenanthroline, it is suggested that ametryne is ineffective at inhibiting electron transfer from Q^?_I to the secondary acceptor ubiquinone when the latter is reduced to the semiquinone form before excitation. (5) At E_h(7.0) > 200 mV, antimycin had a marked effect on the cytochrome b₅₀ reduction-oxidation kinetics but not on the cytochrome c and reaction center changes or the slow phase III of the electrochromic carotenoid change on a 10-ms time scale. This observation appears to rule out a mechanism in which cytochrome b₅₀ oxidation is obligatorily and kinetically linked to the antimycin-sensitive phase of cytochrome c reduction in a reaction involving transmembrane charge transfer at high E_h values. However, at lower redox potentials, cytochrome b₅₀ oxidation is more rapid, and may be linked to the antimycin-sensitive reduction of cytochrome c. (6) It is concluded that neither a simple linear scheme nor a simple Q-cycle model can account adequately for all the observations. Future models will have to take account of a possible heterogeneity of redox chains resulting from the two-electron gate at the level of the secondary quinone, and of the involvement of cytochrome b_?90 in the rapid reactions of the cyclic electron transfer chain     

The occrrence of vesicular-arbuscular mycorrhiza in barley and wheat grown in some Danish soils with different fertilizer treatments

Summary Soil samples, roots and shoots were collected from barley crops at three locations which had received different combinations of N and P for 10 years, and from long-term fertilizer experiments on barley in a sandy soil and on barley and wheat in a loamy soil.Soils were analysed for available P by an anion exchange resin procedure, roots were examined for intensity of VAM infection, and shoots wee analysed for N and P.Vesicualr-arbuscular mycorrhizal infection was found at all locations. It was most abundant at the three locations with least soil-P and lightest at the two locations high in soil-P. Within loocations an inverse relation was found between soil-P level and intensity of infection. Infection was also intensity. by increasing N-fertilizer. Spore counts from selected samples correlated well with infection intensity. Shoot-P did not differ significantly between treatments in spite of significant differences in soil-P. This points to the significance of vesicular-arbuscular mycorrhiza: a lower soil-P level accompanied by a higher infection intensity seem to counterbalance each other to a certain extent.     

Relative addition rate and external concentration; Driving variables used in plant nutrition research

Abstract An increasing literature accounting for various types of experiments indicates that far lower external nutrient concentrations are required by plants than is usually thought to be the case. It is concluded that the ion uptake capacity of the roots, as described by the carrier concept, is high compared to that required for maintenance of the internal concentration. Serious errors in experimental conclusions are associated with insufficient and constant nutrient addition rates. The main errors are caused by non-steady states of the plants both with regard to the internal nutrient concentrations and the relative growth rate. A dynamic concept has been proposed for direct use as the treatment variable within the range of sub-optimum nutrition. The nutritional factor is expressed as a flow, the relative nutrient addition rate in laboratory studies and the nutrient flux density in the field. The experimental use of the relative addition rate has led to steady-state nutrient status and relative growth rate and the interpretation of plant responses which differ fundamentally from accepted views. Thus, for instance, deficiency symptoms disappear, as in natural conditions, when the internal nitrogen concentration is stable, independent of level. The nutrition/growth relationships are very different from those observed when external concentration is varied. The regression line of relative growth rate on relative addition rate passes near to the origin at an angle close to 45 to the axes, which implies that the obtained relative growth rate approximates closely the treatment variable. A striking example of observed differences is the positive effect on nitrogen fixation exerted by high relative nitrogen addition rates compared to the well-known negative effect of increasing external nitrogen concentration. The application of fertilizer on the basis of the nutrient flux density concept provides the possibility of supplying fertilizers corresponding to the consumption potential of the vegetation and to the natural flux density resulting from mineralization in the soil. Nitrogen utilization is high under such conditions and the resulting feedback of nutrition on the mineralization rate suggests that there will be a long-term increase in fertility.