Biogeographic comparisons of marine algal polyphenolics: evidence against a latitudinal trend

Summary Marine allelochemicals generally are present in greater quantity and diversity in tropical than in temperate regions. Marine algal polyphenolics have been reported as an apparent exception to this biogeographic trend, with literature values for phenolic concentrations significantly higher in temperate than in tropical brown algae. In contrast, our results, the first reported for Caribbean brown algae (orders Dictyotales and Fucales), show that many species have high phenolic levels. In addition, both our study and previous studies with north temperate and tropical species demonstrate that there is marked variation in algal phenolic levels within species from different locations. We conclude that high phenolic concentrations occur in species from both temperate and tropical regions, indicating that latitude alone is not a reasonable predictor of plant phenolic concentrations.     

Contrasts between subsurface microbial communities and their metabolic adaptation to polycyclic aromatic hydrocarbons at a forested and an urban coal-tar disposal site

The abundance and distribution of microorganisms and their potential for mineralizing polycyclic aromatic hydrocarbons (PAHs) were measured in subsurface sediment samples at two geographically separate buried coal-tar sites. At a relatively undisturbed forested site in the northeastern United States, metabolic adaptation to the PAHs was evident: Radiolabeled naphthalene and phenanthrene were converted to ¹⁴CO₂ in core material from inside but not outside a plume of groundwater contamination. However, at the urban site in the midwestern United States these PAHs were mineralized in sediments from both contaminated and uncontaminated boreholes. Thus, clear qualitative evidence showing an adaptational response by the subsurface microbial community was not obtained at the urban site. Instead, subtler clues suggesting metabolic adaptation by subsurface microorganisms from the urban site were discerned by comparing lag periods and extents of ¹⁴CO₂ production from radiolabeled PAHs added to samples from contaminated and uncontaminated boreholes. Despite slightly higher PAH mineralization activity in contaminated borehole samples, p-hydroxybenzoate was mineralized equally in all samples from the urban site regardless of location. No striking trends in the abundances of actinomycetes, fungi, and either viable or total bacteria were encountered. However, colonies of the soil bacterium, Bacillus mycoides, were detected on enumeration plates of several samples from unsaturated and saturated zones in both urban boreholes. Furthermore, other common soil bacteria, Myxococcus xanthus and Chromobacterium violaceum, were identified in samples from the uncontaminated urban borehole. The occurrence of bacteria usually restricted to surface soil, combined with the observation of fragments of building materials in many of the core samples, suggested that past excavation and backfilling operations may have caused mixing of surface soil with subsurface materials at the urban site. We speculate that this mixing, as well as non-coal-tar-derived sources of PAHs, contributed to the PAH-mineralizing activity present in the sediment samples from the uncontaminated urban borehole.     

Microbial biomass and activity in subsurface sediments from Vejen,Denmark

Subsurface sediment samples were collected from 4 to 31 m below landsurface in glacio-fluvial sediments from the Quaternary period. The samples were described in terms of pH, electrical conductivity, chloride concentration, organic matter content, and grain size distribution. Viable counts of bacteria varied from 0.5 to 1,203 x 103 colony forming units/g dry weight (gdw); total numbers of bacteria acridine orange direct counts (AODC) varied from 1.7 to 147 × 10⁷ cells/gdw; growth rates (incorporation of [³H]-thymidine) varied from 1.4 to 60.7 × 10⁴ cells/(gdw · day); and rate constants for mineralization of ¹⁴C-labelled compounds varied from 0.2 to 2.3 × 10^–3 ml/(dpm · day) for acetate, and from 0 to 2.0 × 10^–3 ml/(dpm · day) for phenol. Sediment texture influenced the total number of bacteria and potential for mineralization; with increasing content of clay and silt and decreasing content of sand, AODC increased and the mineralization rate declined. Intrinsic permeability calculated from grain size correlated positively with mineralization rate for acetate. Statistical correlation analysis showed high correlations between some of the abiotic parameters, but it was not possible to point out a single abiotic parameter that could explain the variation of size and activity of the microbial population. The microbial data obtained in these geologically young sediments were compared to literature data from older sediments, and this comparison showed that age and type of geological formation might be important for the size and activity of the microbial populations.Offprint requests to: H.-J. Albrechtsen.     

Factors controlling nitrification and denitrification: A laboratory study with gel-stabilized liquid cattle manure

Nitrification and denitrification were studied in a millimeterscale microenvironment using a two-phase system with a liquid manure-saturated layer. Samples consisted of liquid cattle manure and air-dried soil stabilized with silica gel, placed between two aerobic soil phases with a water content near field capacity. A high potential for NH₄ ⁺ oxidation developed within 0–2 mm distance from the interface, and NH₄ ⁺ diffused only 10–20 mm into the soil. Some NH₄ ⁺ was probably immobilized by microorganisms in the soil between 0 and 4 days, after which nitrification was the only sink for NH₄ ⁺. A potential for denitrification developed within the manure-saturated zone. Maximum rates of both potential and actual denitrification were recorded by Day 4, but denitrification continued for at least 2–3 weeks. The potential for nitrification peaked after 14 days. When the pH of the manure was adjusted to 5.5, nitrification was reduced close to the interface, and NH₄ ⁺ penetrated further into the soil before it was oxidized. The pH adjustment had an inhibitory effect on denitrification: Both potential and actual rates of denitrification were almost eliminated for several days. The size of the manure-saturated layer strongly affected denitrification losses. With layers of 8 and 16 mm thickness, losses equivalent to 33 and 40% of the original NH₄ ⁺ pool, respectively, were estimated. When manure corresponding to a 12 mm layer was homogeneously mixed with the soil, only 0.3% was lost.Offprint requests to: S. O. Petersen.     

Seasonal changes in the activation of crossbridge motions of isolated thick filament from Limulus striated muscle

Summary In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL>1 (where K is the scattering vector), the average characteristic linewidth ( ) increased with the addition of Ca²⁺ or with the depletion of ATP. The increase in the with the addition of Ca²⁺ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca²⁺. The increase in which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in following the addition of Ca²⁺ was found to be seasonal, i.e., values of obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in was also different. The increase showed a maximum at about 35°C during the summer and at about 25°C at other times. However, the percentage increase in developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca²⁺ per myosin molecule was 1 during the summer and 2 at other times.Abbreviations DLS dynamic light scattering - L length - K scattering vector - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - average characteristic line width Deceased     

The role of two Trichoderma reesei xylanases in the bleaching of pine kraft pulp

Summary The two major xylanases of Trichoderma reesei with different pI values and pH optima were compared for increasing the bleachability of pine kraft pulp. The efficiencies of the two enzymes acting on pulp substrate were very similar in hydrolysis yield, extraction kappa number or final brightness value. Only slight synergism between the two enzymes was observed in both hydrolysis and bleaching tests. The pH optimum of the pI 5.5 xylanase was similar in pulp treatment and in the hydrolysis of isolated substrates, and the bleaching result also correlated well with the hydrolysis of pulp xylan. By contrast, the pI 9.0 xylanase acted differently on pulp than on isolated xylans at different pH values and the pH optimum on pulp was increased. The bleachability of pulp by the pI 9.0 xylanase was improved more than expected at pH 7.0, although the hydrolysis of pulp xylan was substantially decreased. A similar phenomenon was also observed when the hydrolysis was performed in water instead of buffer. It thus appears that the degree of hydrolysis needed to obtain improved bleachability with pI 9.0 xylanase can be minimized by proper adjustment of the hydrolysis conditions. Correspondence to: J. Buchert     

Plant thioredoxin h: an animal-like thioredoxin occurring in multiple cell compartments

Thioredoxin h has been purified to electrophoretic homogeneity from spinach roots using a procedure devised for leaves. The root thioredoxin (h2 form) differed from chloroplast and animal thioredoxins in showing an atypical active site (Cys-Ala-Pro-Cys) but otherwise resembled animal thioredoxin in structure. Sequence data for a total of 72 residues of spinach root thioredoxin h2 (about 69% of the primary structure) showed 43-44% identity with rabbit and rat thioredoxin. Analysis of cell fractions from the endosperm of germinating castor beans revealed that thioredoxin h occurs in the cytosol, endoplasmic reticulum, and mitochondria. The present findings demonstrate a similarity between plant thioredoxin h and animal thioredoxins in structure and intracellular location and raise the question of whether these proteins have similar functions.     

Recognition of Escherichia coli valine transfer RNA by its cognate synthetase: a fluorine-19 NMR study.

Interactions of 5-fluorouracil-substituted Escherichia coli tRNAVal with its cognate synthetase have been investigated by fluorine-19 nuclear magnetic resonance. Valyl-tRNA synthetase (VRS) (EC 6.1.1.9), purified to homogeneity from an overproducing strain of E. coli, differs somewhat from VRS previously isolated from E. coli K12. Its amino acid composition and N-terminal sequence agree well with results derived from the sequence of the VRS gene [Heck, J.D., & Hatfield, G.W. (1988) J. Biol. Chem. 263, 868-877]. Apparent KM and Vmax values of the purified VRS are the same for both normal and 5-fluorouracil (FUra)-substituted tRNAVal. Binding of VRS to (FUra)tRNAVal induces structural perturbations that are reflected in selective changes in the 19F NMR spectrum of the tRNA. Addition of increasing amounts of VRS results in a gradual loss of intensity at resonances corresponding to FU34, FU7, and FU67, with FU34, at the wobble position of the anticodon, being affected most. At higher VRS/tRNA ratios, a broadening and shifting of FU12 and of FU4 and/or FU8 occur. These results indicate that VRS interacts with tRNAVal along the entire inside of the L-shape molecule, from the acceptor stem to the anticodon. Valyl-tRNA synthetase also causes a splitting of resonances FU55 and FU64 in the T-loop and stem of tRNAVal, suggesting conformational changes in this part of the molecule. No 19F NMR evidence was found for formation of the Michael adduct between VRS and FU8 of 5-fluorouracil-substituted tRNAVal that has been proposed as a common intermediate in the aminoacylation reaction.     

Image processing software for enhanced visualization of faint or noisy autoradiographic images

A computer program for digital image processing is described which can be implemented using scanning densitometer hardware pre-existing in most biology departments plus computer video hardware which may either pre-exist in the biology department or would represent a moderate upgrade over an already planned computer purchase. The primary purpose of this computer program is to provide contrast enhancement of faint or low contrast autoradiograph images and to implement background subtraction and digital smoothing methods which permit visualization of blurry electrophoresis bands against noisy backgrounds. However, the program also has modest editing capabilities that allow its use in the routine preparation of images for publication. Finally, the program has facilities for deblurring, edge enhancement and multiple image averaging, which give it usefulness in other forms of photographic analysis.     

Inhibition of endotoxin-induced monocytic procoagulant activity by n-alcohols and anesthetics.

1. The effect of n-alcohols (methanol and ethanol) and anesthetics (lidocaine, thiopental, methohexital and thiamylal) on procoagulant activity (PCA) in human peripheral-blood monocytes and non-adherent cultured leukemia promonocytic U937 and THP-1 cells was examined herein. 2. Exposure of whole blood to ethanol showed no effect on PCA in human monocytes. However, ethanol dose-dependently inhibited LPS-induced PCA in isolated human monocytes. 3. In THP-1 cells, ethanol had no significant effect on PCA in either non-challenged or LPS-induced status. However, the induction of PCA by LPS was substantially inhibited when cells were pretreated with 1% ethanol (v/v) for 72 hr. 4. In U937 cells, n-alcohols and anesthetics resulted in dose-dependent depressions in PCA. Importantly, the percent reduction in LPS-induced PCA was much more pronounced than that in non-challenged PCA. 5. These data clearly suggest that n-alcohols and anesthetics readily inhibit the LPS-stimulatory action on monocytic PCA.