The extraction by soil and absorption by plants of applied zinc and cadmium

In five consecutive years lettuce, spinach, spring wheat, endive and maize were grown in pots and the effects of native and soil-applied Zn and Cd on plant Zn and Cd concentrations were studied. The normal interactive pattern was antagonistic, Zn reducing plant Cd uptake, and conversely, but less so. Only in loam soil Zn and Cd were synergistic to some extent, plant Zn uptake increasing with applied Cd.When relating total soil Cd/Zn to plant Cd/Zn separate sets of data could be distinguished for loam and sandy soil, each fitting a straight line. The use of 0.1 M CaCl₂ instead of total extractable soil Cd/Zn makes the two sets of data to coalesce around a single straight line. All crops were found to show a positive linear relationship between 0.1 M CaCl₂-extractable soil Cd/Zn and plant Cd/Zn.     

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.     

Variation in tissue element concentrations in Quercus ilex L. over a range of different soils

In order to study the variability in nutrient concentrations in four tissues of Q. ilex in relation to soil properties, we selected fifteen stands in both Quercus ilex forests and Q. ilex-Pinus halepensis mixed forests. These stands had developed on soils derived from eight different parent materials. Three soil groups were differentiated according to their chemical properties: calcareous soils, siliceous soils, and volcanic soils. Across sites, nutrient concentrations were generally less variable in current-year tissues than in older tissues. Nitrogen and potassium showed the lowest variability among sites, their concentrations in current-year leaves ranging from 1.17% to 1.39% for N and from 0.53% to 0.68% for K. There were few statistically significant correlations between tissue element concentrations, the most frequent being the antagonistic relationship between calcium and magnesium. Nitrogen concentration in current-year leaves was negatively correlated with soil chemical fertility (nitrogen, phosphorus and potassium). This may reflect a nutritional imbalance between nitrogen and other nutrients, some of which may be more limiting than nitrogen to Q. ilex growth in Catalonia forests. Negative correlations were also found between plant magnesium and soil calcium, and positive correlations between plant calcium and soil calcium.     

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     

Bacteriopheophytin c in reaction center complexes of green photosynthetic bacteria

Two reaction center complexes prepared from cytoplasmic membranes of Chlorobium limicola f. thiosulfato-philum were compared by absorption and CD spectrophotometry. Bacteriopheophytin c (670 nm), which is optically active in one complex but not in the other, may serve as a secondary electron acceptor in the reaction center.     

The photoreaction center of Rhodospirillum rubrum mutant strain F24.1

Rhodospirillum rubrum strain F24.1 is a spontaneous revertant of nonphototrophic mutant F24 derived from wild-type strain S1. Strain F24 shows no detectable photochemical activity and contains, at most, traces of the photoreaction center polypeptides. Strain F24.1 has a phototrophic growth rate close to that of the wild-type strain (Picorel, R., del Valle-Tascón, S. and Ramírez, J.M. (1977) Arch. Biophys. Biochem. 181, 665–670) but shows little photochemical activity. Light-induced absorbance changes in the near-infrared, photoinduced EPR signals and ferricyanide-elicited absorbance changes indicate that strain F24.1 has a photoreaction center content of 7–8% as compared to strain S1. Polyacrylamide gel electrophoresis of isolated F24.1 chromatophores shows the photoreaction center polypeptides to be present in amounts compatible with this value. Photoreaction center was prepared from strain F24.1 and showed no detectable difference with that of strain S1. It is concluded that strain F24.1 photosynthesis is due entirely to its residual 7–8% of typical photoreaction center.     

The photosynthetic electron transfer chain of Chromatium vinosum chromatophores flash-induced cytochrome b reduction

Reduction of a cytochrome b following excitation by a single, short, near-saturating light flash has been demonstrated in Chromatium vinosum chromatophores. The extent of reduction is increased by addition of antimycin. The cytochrome has an α-band maximum at 562 nm in the presence of antimycin.The cytochrome b reduction is most readily observed in the presence of antimycin at high redox potential when cytochrome c-555 is oxidised before excitation. Under these conditions the half-time for reduction is about 20 ms, and the extent is about 0.5 mol of cytochrome b reduced per mol of reaction center oxidised. This extent of reduction is observed on the first flash-excitation from the dark-adapted state, and there was no indication that the reaction center quinone acceptor complex acted as a two-electron accumulating system. With cytochrome c-555 reduced before excitation, the extent of cytochrome b reduction is approximately halved. The factors which result in substoichiometric cytochrome b reduction are not yet understood.Agents which appear to inhibit primary acceptor oxidation by the secondary acceptor (UHDBT, PHDBT, DDAQQ, HOQNO, o-phenanthroline), inhibit reduction of the cytochrome b. DBMIB inhibits cytochrome b reduction but does not appear to inhibit primary acceptor oxidation.These observations confirm that a cytochrome b receives electrons delivered from the primary acceptor complex, and indicate that the photoreduced cytochrome b is reoxidised via an antimycin-sensitive pathway.     

The role of soluble cytochrome c-551 in cyclic electron flow-driven active transport in Chromatium vinosum

Spheroplasts have been prepared from the photosynthetic purple sulfur bacterium Chromatium vinosum by lysozyme plus ethylenediaminetetraacetic acid treatment. These spheroplasts are able to take up alanine in the light, but light-dependent alanine uptake is lost upon subsequent washing of the spheroplasts. The observations that alanine uptake driven by a potassium plus valinomycin-induced membrane potential (outside positive) is not affected by washing and that light-dependent alanine uptake can be restored by addition of the supernatant from washing suggest that a soluble electron carrier is lost during washing. Light-dependent alanine uptake in washed spheroplasts could be restored by addition of C. vinosum cytochrome c-551. Other soluble electron carriers from C. vinosum (high-potential iron protein, cytochrome ‘f’, cytochrome c′ and the flavocytochrome c-552) did not restore alanine uptake nor did a variety of other soluble electron carrier proteins from other organisms. These results suggest that cytochrome c-551 functions as an electron carrier in the cyclic electron transfer chain of C. vinosum. Mitochondrial cytochrome c (equine heart) and cytochrome c-551 from Pseudomonas aeruginosa were highly effective in restoring light-dependent alanine uptake in washed spheroplasts, making it likely that C. vinosum cytochrome c-551 is related by evolution to the same cytochrome c family as these other two c cytochromes.