Transport of groundwater-borne nutrients from watersheds and their effects on coastal waters

Anthropogenic activities on coastal watersheds increase nutrient concentrations of groundwater. As groundwater travels downslope it transports these nutrients toward the adjoining coastal water. The resulting nutrient loading rates can be significant because nutrient concentrations in coastal groundwaters may be several orders of magnitude greater than those of receiving coastal waters. Groundwater-borne nutrients are most subject to active biogeochemical transformations as they course through the upper 1 m or so of bottom sediments. There conditions favor anaerobic processes such as denitrification, as well as other mechanisms that either sequester or release nutrients. The relative importance of advective vs. regenerative pathways of nutrient supply may result in widely different rates of release of nutrients from sediments. The relative activity of denitrifiers also may alter the ratio of N to P released to overlying waters, and hence affect which nutrient limits growth of producers. The consequences of nutrient (particularly nitrate) loading include somewhat elevated nutrient concentrations in the watercolumn, increased growth of macroalgae and phytoplankton, reduction of seagrass beds, and reductions of the associated fauna. The decline in animals occurs because of habitat changes and because of the increased frequency of anoxic events prompted by the characteristically high respiration rates found in enriched waters.     

Hemolysis of rabbit erythrocytes in the presence of copper ions

The hemolysis of red blood cells (RBC) induced by Cu(II) is modified by ceruloplasmin (Cp) and albumin. The time course of hemolysis for rabbit RBC by Cu(II) consisted of two parts, an induction period followed by a catastrophic lysis period. The induction period decreased and the lysis rate increased with increasing Cu(II) concentration. Cp or albumin, modified Cu(II) induced hemolysis, by increasing the duration of the induction period and decreasing the overall rate of hemolysis of RBC. The catastrophic lysis period coincided with a sharp increase in the formation of metHb within the cell and in a rapid uptake of Cu(II). The presence of Cp led to an increase in the induction period prior to the rapid increase in metHb formation and in Cu(II) uptake. Porcine Cp was prepared with either two or three nonprosthetic copper binding sites (sites where Cu(II) is easily removed by passing over Chelex-100). Cp with three nonprosthetic binding sites gave more protection than Cp with two. Likewise, albumin can be prepared with three and five nonprosthetic copper binding sites. The albumin with five sites gave more protection than the albumin with three sites.     

Soluble metals in the atmosphere and their biological implications

Multivariate statistical analysis has been applied to time series measurements of aerosol elemental composition from PIXE analysis of filter samples, and principal components have been resolved that represent distinct particle types in an external mixture in the atmosphere. In this study, it is argued that a combination of chemical and statistical analyses of the data may be more powerful in determining chemical species in atmospheric aerosols than studies that employ mainly direct chemical analysis of chemical species in unresolved mixtures of aerosol particle samples. Sulfur is generally associated with mineral dust elements. It is reasoned that the association may represent sulfuric acid coatings on particles that can lead to mineral dissolution and solubilization of significant amounts of aluminum, iron, and other metals. Upon wet or dry deposition to the surface, the fluxes of these metals in biologically-available form may be sufficient to affect primary productivity in the world ocean and cause ecological damage in lakes. As a consequence, the fluxes of biogenic trace gases to the atmosphere may be changed, possibly leading to changes in the tropospheric concentration of ozone. The inputs to lakes of soluble aluminum, which is toxic to fish, may be partly by deposition directly from the atmosphere, thus not limited to leaching of soils by acid deposition. Human inhalation of soluble aluminum and other solulilized mineral metals may account, in part, for the observed geographic pattern of deaths attributed to chronic obstructive pulmonary disease (COPD) that show high rates in cities of the Western US and the southeast region, but low in most of the midwest and northeast.     

Analysis of an ABA-responsive rice gene promoter in transgenic tobacco

We have analyzed in transgenic tobacco the expression of a chimeric gene containing 5 sequences of the rice rab-16B gene fused to the -glucuronidase (GUS) reporter gene. This construct, a translational fusion (–482 to +184) including 14 amino acids of the RAB-16B protein, is expressed only in zygotic and pollen-derived embryos. In zygotic embryos, GUS activity begins to accumulate 10 days after flowering (daf), and increases until seed maturation at 25 daf. Immunological measurements of endogenous abscisic acid (ABA) accumulation in these seeds showed a close parallel between hormone levels and GUS activity. However, GUS activity could not be reproducibly induced by treatment of immature embryos with ABA (10 M). Neither GUS activity nor GUS mRNA could be detected in leaves of transgenic tobacco even after ABA treatment. In contrast, GUS activity could be induced to high levels in pollen-derived embryos by treatment with ABA. Our results show that 482 bp of 5 sequences of the rice rab-16B promoter can confer in transgenic tobacco developmentally regulated expression in embryos but not ABA-responsive expression in vegetative tissues.     

Optimization of delivery of foreign DNA into higher-plant chloroplasts

We report here an efficient and highly reproducible delivery system, using an improved biolistic transformation device, that facilitates transient expression of -glucuronidase (GUS) in chloroplasts of cultured tobacco suspension cells. Cultured tobacco cells collected on filter papers were bombarded with tungsten particles coated with pUC118 or pBI101.3 (negative controls), pBI505 (positive nuclear control) or a chloroplast expression vector (pHD203-GUS), and were assayed for GUS activity. No GUS activity was detected in cells bombarded with pUC118 or pBI101.3. Cells bombarded with pBI505 showed high levels of expression with blue color being distributed evenly throughout the whole cytosol of the transformants. pHD203-GUS was expressed exclusively in chloroplasts. We base this conclusion on: i) the procaryotic nature of the promoter used in the chloroplast expression vector; ii) delayed GUS staining; iii) localization of blue color within subcellular compartments corresponding to plastids in both shape and size; and iv) confirmation of organelle-specific expression of pHD203-GUS using PEG-mediated protoplast transformation. Chloroplast transformation efficiencies increased dramatically (about 200-fold) using an improved helium-driven biolistic device, as compared to the more commonly used gun powder charge-driven device. Using GUS as a reporter gene and the improved biolistic device, optimal bombardment conditions were established, consistently producing several hundred transient chloroplast transformants per Petri plate. Chloroplast transformation efficiency was found to be increased further (20-fold) with supplemental osmoticum (0.55 M sorbitol and 0.55 M mannitol) in the bombardment and incubation medium. This system provides a highly effective mechanism for introducing and expressing plasmid DNA within higher-plant chloroplasts, and the fact that GUS functions as an effective marker gene now makes many genetic studies possible which were not possible before.     

The induction of lincomycin resistance in Lycopersicon peruvianum and Lycopersicon esculentum

Lincomycin-resistant calli were induced from both Lycopersicon esculentum and Lycopersicon peruvianum using N-mitroso-N-methylurea (NMU) mutagenesis. From these calli lincomycin-resistant plants were regenerated. For L. peruvianum it was shown that the resistant plants could be divided in two classes with respect to their resistance to lincomycin and its derivative clindamycin. The first class comprised plants which were resistant to 500 mg/l lincomycin and showed no shoot or root formation in the presence of clindamycin; the second class consisted of plants resistant to 2000 mg/l lincomycin and these plants were able to form shoots and roots on clindamycin containing media. Lincomycin is an inhibitor of peptidyltransferase; chloroplast encoded parts of this enzymatic function are sensitive for this antibiotic. Reciprocal crosses between our lincomycin resistant and wild type L. peruvianum plants indicated a maternal inheritance of the mutation.     

Isolation and characterization of the membrane-bound cytochrome c-554 from the thermophilic green photosynthetic bacterium Chloroflexus aurantiacus

The membrane-bound photooxidizable cytochrome c-554 from Chloroflexus aurantiacus has been purified. The purified protein runs as a single heme staining band on SDS-PAGE with an apparent molecular mass of 43 000 daltons. An extinction coefficient of 28 ± 1 mM^–1 cm^–1 per heme at 554 nm was found for the dithionite-reduced protein. The potentiometric titration of the hemes takes place over an extended range, showing clearly that the protein does not contain a single heme in a well-defined site. The titration can be fit to a Nernst curve with midpoint potentials at 0, +120, +220 and +300 mV vs the standard hydrogen electrode. Pyridine hemochrome analysis combined with a Lowry protein assay and the SDS-PAGE molecular weight indicates that there are a minimum of three, and probably four hemes per peptide. Amino acid analysis shows 5 histidine residues and 29% hydrophobic residues in the protein. This cytochrome appears to be functionally similar to the bound cytochrome from Rhodopseudomonas viridis. Both cytochrome c-554 from C. aurantiacus and the four-heme cytochrome c-558-553 from R. viridis appear to act as direct electron donors to the special bacteriochlorophyll pair of the photosynthetic reaction center. They have a similar content of hydrophobic amino acids, but differ in isoelectric point, thermodynamic characteristics, spectral properties, and in their ability to be photooxidized at low temperature.Abbreviations LDAO lauryl dimethyl amine-N-oxide - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - mV millivolt - E_m.8 midpoint potential at pH 8.0 - ODV optical density x volume in ml     

Fluorescence lifetimes of dimers and higher oligomers of bacteriochlorophyll c from Chlorobium limicola

Fluorescence lifetimes have been measured for bacteriochlorophyll (BChl) c isolated from Chlorobium limicola in different states of aggregation in non-polar solvents. Two different homologs of BChl c were used, one with an isobutyl group at the 4 position, the other with n-propyl. Species previously identified as dimers (Olson and Pedersen 1990, Photosynth Res, this issue) decayed with lifetimes of 0.64 ns for the isobutyl homolog, 0.71 ns for n-propyl. Decay-associated spectra indicate that the absorption spectrum of the isobutyl dimer is slightly red-shifted from that of the n-propyl dimer. Aggregates absorbing maximally at 710 nm fluoresced with a principal lifetime of 3.1 ns, independent of the homolog used. In CCl₄, only the isobutyl homolog forms a 747-nm absorbing oligomer spectrally similar to BChl c in vivo. This oligomer shows non-exponential fluorescence decay with lifetimes of 67 and 19 ps. Because the two components show different excitation spectra, the higher oligomer is probably a mixture of more than one species, both of which absorb at 747 nm.Abbreviations BChl bacteriochlorophyll - Chl chlorophyll - % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGGipm0dc9vqaqpepu0xbbG8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeq4Xdm2aaW% baaSqabeaacaaIYaaaaaaa!3777!\[\chi ^2 \] chi-square - FWHM full-width at half-maximum