Growth measurements of terrestrial microbial species by a continuous-flow technique

A continuous nutrient flow system has been developed to measure microbial activity in soil with various concentrations of added substrate. The system consists of a thin soil layer through which substrate was added continuously over periods up to 4.5 days. Substrate utilization was determined by effluent analysis. Respiration was measured manually by injecting a sample into a gas chromatograph or automatically by coupling the growth chamber to a computer-controlled gas sampling valve. This permitted respiratory CO₂ to be measured by the gas chromatograph at intervals selected by the investigator. Software controlling the valve and gas chromatograph not only automated gas phase sampling, but also provided a scan of CO₂ evolution and a preliminary data summary. This included the date and time of sample, peak height, and percent CO₂ in the gas phase. Data for growth on glucose using a microbial population native to a California annual grassland soil demonstrated that the direct cell count and respiratory techniques for biomass estimation give comparable results. This procedure provides the potential for detailed analyses of substrate utilization in studies of the growth and maintenance of soil microorganisms.     

Influence of various soil factors on the effects of ferulic acid on leaf expansion of cucumber seedlings

Summary Cucumber seedlings were grown in a Portsmouth soil-sand system to study how varying soil clay and organic matter content might modify cucumber seedling response to ferulic acid, a reported allelopathic agent. Leaf area expansion of cucumber seedlings, soil respiration, and soil solution concentrations of ferulic acid were monitored. Leaf area, mean absolute rates of leaf expansion, and shoot dry weight of cucumber seedlings were significantly reduced by ferulic acid concentrations ranging from 10 to 70 μg/g dry soil. Ferulic acid was applied every other day, since it rapidly disappeared from soil solution as a result of retention by soil particles, utilization by microbes and/or uptake by roots. The amount of ferulic acid retained (i.e., adsorbed, polymerized,etc.) by soil particles appeared to be secondary to microbial utilization and/or uptake by roots. Varying clay (5.3 to 9.8 g/cup) and organic matter (2.0 to 0.04g/cup) contents of the soil appeared to have little impact on the disappearance of ferulic acid from soil solution under “ideal” growth conditions for cucumber seedlings unless larger amounts of ferulic acid were added to the soil; in this case 200 μg/g. The addition of ferulic acid to the soil materials substantially increased the activity of the soil microbes. This latter conclusion is based on recovery of ferulic acid from soil solution and soil respiration measurements. Paper No. 10347 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, N C 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the product named, nor criticism of similar ones not mentioned.     

Prediction of heavy-metal concentrations in mature plants by chemical analysis of seedlings

Five plant species were cultivated on a soil from the Neckar alluvial fan near Heidelberg (FRG) polluted by the emissions of a cement plant. Thallium, cadmium and lead concentrations in seedlings and mature plants were determined by atomic absorption analysis. AdditionallyBrassica napus L.napus was grown on soils containing 5 different concentrations of heavy metals, achieved by mixing two similar soils, from the same area but with different metal concentrations. Thallium and cadmium were shown to be taken up by roots whilst lead which was also absorbed, was deposited mainly on the plant surface. However during cultivation in the winter months, a remarkable deposit of lead via the roots was found. Thallium in the soil from a anthrorogen source was more available to plants than thallium of geological origin. During the lifetime of a plant concentrations of thallium and cadmium were always highest in the seedling. The decrease in metal concentration with maturity depended on the plant species and the element, but was not a function of the metal concentration in the soil.     

Spinach ferredoxin is a calcium-binding protein

Spinach-leaf ferredoxin was identified as a calcium-binding protein by ⁴⁵Ca autoradiography on nitrocellulose membranes and with the cationic carbocyanine dye 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naphtho[1,2-d]thiazolium bromide (stains-all). Binding of ⁴⁵Ca was observed at pH 6.8 and pH 7.8 and in the presence of 5 mM and 20 mM MgCl₂. At the higher MgCl₂ concentration the Ca²⁺-binding capacity is reduced. Only micromolar concentrations of LaCl₃, however, are required to achieve a similar effect. Both the oxidized and reduced forms of ferredoxin bind calcium.Abbreviations PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate - stains-all 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naptho[1,2-d]thiazolium bromide     

Expression of the β-subunit of β-conglycinin in seeds of transgenic plants

Soybean (Glycine max (L.) Merr.) seeds contain the storage protein -conglycinin, encoded by a multigene family. -Conglycinin consists of three subunits; , , and . A genomic clone for a -subunit of -conglycinin has been characterized by restriction-enzyme mapping and hybrid selected in-vitro translation followed by immunoprecipitation. In order to determine the developmental regulation of this -subunit gene, its expression was studied in seeds of transgenic petunia (Petunia hybrida) and tobacco (Nicotiana tabacum L.) plants. The -subunit expressed in seeds of petunia and tobacco was recognized by anti--conglycinin serum at a relative molecular mass of 53 000, equivalent to that of the native protein. Separation of the petunia-seed proteins by isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis showed that multiple isoelectric forms of the -subunit were produced. There was approximately a twofold variation in the accumulation of the -subunit protein in the mature seeds of transgenic petunia plants, each containing a single -subunit gene. However, the level of protein accumulation in mature seeds and the amount of -subunit mRNA in developing seeds was not correlated. Accumulation of the -subunit protein in transgenic seeds was less than the -subunit protein that accumulated in transgenic petunia seeds containing a single -subunit gene and less than the amount of the -subunit in mature soybean seeds which contain 8–13 -subunit genes. In transgenic tobacco plants, the accumulation of the -subunit protein in seeds was generally well correlated with the number of genes that were incorporated in the different transformants.Abbreviations kb kilobase - kDa kilodalton - M_r relative molecular mass - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis     

C-banding polymorphism and the analysis of nucleolar activity in Dasypyrum villosum (L.) Candargy,its added chromosomes to hexaploid wheat and the amphiploid Triticum dicoccum — D. villosum

Summary C-banding patterns and nucleolar activity were analyzed in Dasypyrum villosum, its added chromosomes to hexaploid wheat and the hexaploid amphiploid Triticum dicoccum-D. villosum. Two different populations of the allogamous species D. villosum (2n= 14, VV) from Greece and Italy were analyzed showing a similar polymorphism for C-banding pattern. Six of the seven addition lines were identified by their characteristic C-banding pattern. No polymorphism between both members of each added alien chromosome was found. Furthermore, nucleolar activity and competition were studied by using silver staining procedure. In D. villosum only one chromosome pair, A, was found to be responsible for organizing nucleoli. The results obtained in the amphiploid and in the addition lines demonstrate that nucleolar activity is restricted to SAT-chromosomes 1B and 6B of wheat, while those of D. villosum remain inactive.     

Alga consumption of four dominant planktonic crustaceans in Lake Balaton (Hungary)

Between 1981–83 the gut contents ofDaphnia galeata, D. cucullata, Eudiaptomus gracilis, andCyclops vicinus were examined with light and scanning electron microscope to obtain information on the feeding of these species in Lake Balaton. The twoDaphnia species feed mainly on abioseston, and it is assumed that their primary nutrient source was organic matter adsorbed onto the surfaces of the abioseston granules plus bacteria and detritus.E. gracilis feeds on algae, showing a preference for green algae and diatoms.C. vicinus is also a prodigious consumer of algae in Lake Balaton, utilizing the whole size spectrum of phytoplankton. Concerning the trophic relationships between phytoplankton and zooplankton in Lake Balaton, that between diatoms and bothE. gracilis andC. vicinus is the most conspicouos. Convincing evidence for an extensive utilization of blue-green algae was not found. Though there is no firm evidence yet, it is likely that theDaphnia are dependent on organic matter adsorbed on the abioseston.     

Effect of rainstorms on heterotrophic bacterial activity in a hypertrophic African lake

Hartbeespoort Dam is a hypertrophic man-made lake which is located in the Transvaal Province of South Africa. This region has recently experienced its most severe drought of the century. However, on three occasions in the summer rainy seasons of 1984 and 1985, major rainfalls (> 50 mm) occurred which caused large inflows to the lake. Inflowing river water entered as a density current causing marked silting of the water. Within the epilimnion (0–10 m) prior to these rainfalls there was usually no variation of bacterial numbers with depth, but heterotrophic bacterial activity (glucose uptake) decreased with depth concomitant with primary production. With the increased river inflow bacterial numbers did not increase but bacterial activity at the bottom of the epilimnion (10 m) increased to as high as 2.7 µg C l^–1 h^–1 in January 1985, reversing the depth profile of bacterial activity within the epilimnion. This resulted in decreased glucose concentrations (K_t + S_n) and turnover times. Heterotrophic activity per cell increased by between 2.5 and 5 times. These data demonstrate that storm events are important phenomena causing short-term changes in the metabolic activity of planktonic heterotrophic bacteria in lakes.     

D2O and the sodium pump in squid nerve membrane

Summary In 10 K artificial seawater (ASW). D₂O replacement reduced the Na efflux of squid axons by about one third. In 0 K ASW, D₂O replacement had little effect. D₂O reduced the K⁺ sensitivity of the efllux but increased the affinity for K⁺. A 4° decrease in temperature mimicked the effects of D₂O. When axons were injected with arginine, to decrease the ATP/ADP ratio, they lost K⁺ sensitivity in normal ASW, as expected. Their efflux into 0 K ASW became D₂O sensitive. The results are discussed in terms of conformational changes in the Na pump molecular complex.     

Modulation of water and urea transport in human red cells: Effects of pH and phloretin

Summary It has previously been shown by Macey and Farmer (Biochim. Biophys. Acta 211:104–106, 1970) that phloretin inhibits urea transport across the human red cell membrane yet has no effect on water transport. Jennings and Solomon (J. Gen. Physiol. 67:381–397, 1976) have shown that there are separate lipid and protein binding sites for phloretin on the red cell membrane. We have now found that urea transport is inhibited by phloretin binding to the lipids with aK ₁ of 25±8 m in reason-able agreement with theK _D of 54±5 m for lipid binding. These experiments show that lipid/protein interactions can alter the conformational state of the urea transport protein. Phloretin binding to the protein site also modulates red cell urea transport, but the modulation is opposed by the specific stilbene anion transport inhibitor, DIDS (4,4-diisothiocyano-2,2-stilbene disulfonate), suggesting a linkage between the urea transport protein and band 3. Neither the lipid nor the protein phloretin binding site has any significant effect on water transport. Water transport is, however, inhibited by up to 30% in a pH-dependent manner by DIDS binding, which suggests that the DIDS/band 3 complex can modulate water transport.