Soil organic carbon is not just for soil scientists: measurement recommendations for diverse practitioners.

Soil organic carbon (SOC) regulates terrestrial ecosystem functioning, provides diverse energy sources for soil microorganisms, governs soil structure, and regulates the availability of organically bound nutrients. Investigators in increasingly diverse disciplines recognize how quantifying SOC attributes can provide insight about ecological states and processes. Today, multiple research networks collect and provide SOC data, and robust, new technologies are available for managing, sharing, and analyzing large data sets. We advocate that the scientific community capitalize on these developments to augment SOC data sets via standardized protocols. We describe why such efforts are important and the breadth of disciplines for which it will be helpful, and outline a tiered approach for standardized sampling of SOC and ancillary variables that ranges from simple to more complex. We target scientists ranging from those with little to no background in soil science to those with more soil-related expertise, and offer examples of the ways in which the resulting data can be organized, shared, and discoverable.

Effectiveness of biochar for sorption of ammonium and phosphate from dairy effluent.

The use of biochar for recovery of excess nutrients in dairy manure effluent and the use of nutrient-enriched biochar as soil amendment can offer a robust solution for multiple environmental issues. In this study we determined the capacity of biochar, produced by pyrolyzing mixed hardwood feedstock at 300°C, to adsorb and retain or release two major nutrient ions: ammonium (NH) and phosphate (PO). We conducted the experiment using a range of nutrient concentrations that represent those commonly observed in dairy manure effluent (0-50 mg L for PO and 0-1000 mg L for NH). Up to 5.3 mg g NH and 0.24 mg g PO was adsorbed from manure by biochar (18 and 50% of total amount in the manure slurry, respectively). During the desorption phase of the experiment, biochar retained 78 to 91% of the sorbed NH and 60% of the sorbed PO at reaction times <24 h. Our findings confirm that biochar can be used for recovering excess nitrogen and phosphorus from agricultural water, such as dairy manure effluent.

Phosphate permeases of Saccharomyces cerevisiae.

The PHO84 and PHO89 genes of Saccharomyces cerevisiae encode two high-affinity phosphate cotransporters of the plasma membrane. Hydropathy analysis suggests a secondary structure arrangements of the proteins in 12 transmembrane domains. The derepressible Pho84 and Pho89 transporters appear to have characteristic similarities with the phosphate transporters of Neurospora crassa. The Pho84 protein catalyzes a proton-coupled phosphate transport at acidic pH, while the Pho89 protein catalyzes a sodium-dependent phosphate uptake at alkaline pH. The Pho84 transporter can be stably overproduced in the cytoplasmic membrane of Escherichia coli, purified and reconstituted in a functional state into proteoliposomes.

Molecular charge effects on the protein permeability of the guinea-pig placenta.

The effect of molecular charge on protein permeability of the dually perfused guinea-pig placenta has been investigated by measurement of the permeability surface area products (PS) and observation of the ultrastructural localization of cationic horseradish peroxidase (cHRP) and anionic horseradish peroxidase (aHRP) molecules. Steady-state PS calculated from the experimental data was 0.032 +/- 0.0045 and 0.0045 +/- 0.0008 ml min-1 (mean +/- s.e.m.) for cHRP and aHRP respectively (P less than 0.01). The PS for a diffusional marker, 51Cr-ethylenediaminetetraacetic acid, showed no significant difference between the two groups. Ultrastructurally, placentae perfused with cHRP showed fewer microvilli and a dilated interstitial space compared with placentae perfused with aHRP; large vacuoles were also found in the syncytiotrophoblast in the former but not in the latter tissue. Reaction product in placentae perfused with cHRP was localized to the maternal-facing plasma membrane of the syncytiotrophoblast, in vacuoles and vesicles of the syncytiotrophoblast, and also in the basement membrane of the interstitial space, whereas placentae perfused with aHRP only had reaction product in vesicles in the syncytiotrophoblast. These results suggest that anionic sites in the guinea-pig placenta affect its permeability to charged proteins, cationic molecules inducing structural changes associated with increased permeability.

Expression and purification of the high-affinity phosphate transporter of Saccharomyces cerevisiae.

The plasma membrane high-affinity phosphate permease of Saccharomyces cerevisiae has been overproduced as a stable membrane-bound chimeric protein in Escherichia coli. Construction of a chimera between the permease and a peptide containing 10 consecutive histidine residues allowed selective binding of the chimera to a chelating column charged with Ni2+, and elution with imidazole in a high state of purity. Approximately 5 mg purified His10-permease was obtained from 3 g (wet mass) cells. The purified phosphate permease chimera catalyzes uncoupler-sensitive phosphate transport after reconstitution into proteoliposomes.

Isolation and characterization of membrane vesicles of Saccharomyces cerevisiae harboring the high-affinity phosphate transporter.

Membrane vesicles with an inside-out orientation were isolated from the plasma membrane of Saccharomyces cerevisiae by an improved aqueous two-phase partitioning technique. The activity of the orthovanadate-sensitive H+-pumping ATPase, the plasma membrane marker, was highly enriched by the partitioning technique. The obtained results suggest that the membrane vesicles produced were predominantly oriented inside-out. The isolated plasma membrane vesicles displayed cross-reactions with antibodies raised against synthetic peptide corresponding to the N-terminal (residues 1-10) and the C-terminal (residues 578-597) regions of the plasma membrane phosphate transporter encoded by the PHO84 gene and the H+-pumping ATPase of S. cerevisiae. The purified membrane vesicles catalyzed a derepressible inhibitor-sensitive phosphate uptake at levels comparable with the situation in intact cells of S. cerevisiae indicating that transport of phosphate across the membrane is both functional and bidirectional. The PHO84 transporter harbored in isolated plasma membranes could moreover be enriched in a high state of purity by immunoaffinity chromatography using immobilized anti-PHO84 antibodies.

Effects of histamine on vascular resistance and protein permeability in the isolated dually perfused guinea-pig placenta.

The possibility that histamine can affect both the vascular resistance and permeability of the isolated dually perfused guinea-pig placenta has been investigated. Change from control to histamine (2.7 x 10(-4)M) perfusion of the fetal circulation elicited a significant (P less than 0.01, paired 't' test) maximum increase of 1.17 +/- 0.14 (SEM) kPa in fetal perfusion pressure 3 min later, representing a 33% rise. This vasoconstriction was completely blocked by the H1 antagonist diphenhydramine (10(-4)M) but not by the H2 receptor antagonist cimetidine (10(-4)M). In the same experiments the clearance (calculated as the ratio of fetal to maternal perfusate concentration times fetal flow-rate) of a macromolecular tracer, anionic horseradish peroxidase from the maternal to fetal circulation was significantly increased (P less than 0.05, paired 't' test) when steady state (15-20 min of perfusion) values were compared, from 5.9 +/- 1.7 (SEM) microliter min-1 placenta-1 to 12.9 +/- 3.5 (SEM) microliter min-1 placenta-1 (n = 20) for control and histamine respectively. By contrast the steady state clearance (calculated as before) of a smaller hydrophilic tracer, 51Cr-EDTA, was not significantly affected, being 587 +/- 59 (SEM) microliter min-1 placenta-1 in control and 587 +/- 55 (SEM) microliter min-1 placenta-1 (n = 20) with histamine perfusion. When histamine was perfused simultaneously with an H1 or H2 antagonist there was no change in anionic horseradish peroxidase clearance. Electron microscopy of placentas perfused with histamine failed to reveal any obvious alteration in morphology or anionic horseradish peroxidase localisation as compared to placenta perfused without histamine. This study thus demonstrates that histamine may cause changes in the macromolecular permeability of the placenta as well as vasoconstriction of the placental vasculature.

Isolation and characterization of a novel leaf-inhabiting osmo-, salt-, and alkali-tolerant Yarrowia lipolytica yeast strain.

Salt-excreting leaves of Atriplex halimus plants harvested in the central Negev Highlands of Israel were screened for yeasts inhabiting their surfaces. Several aerobic, moderately salt- and alkali-tolerant yeasts were isolated. One of the isolates (tentatively designated S-8) was identified as Yarrowia lipolytica (Wick.) van der Walt and Arx, on the basis of its morphological, biochemical/physiological characteristics, and of quantitative chemotaxonomic and molecular marker analyses. However, the strain is distinguished from the known members of the type Y. lipolytica strain by its pronounced osmo-, salt-, and pH tolerance. Cells displayed a unique capacity to grow over a wide pH range (from 3.5 to 11.5) with a pH optimum at 4.5 to 7.5. It is proposed that the S-8 strain be assigned to a single Y. lipolytica species as its anamorpha, or as a new variety, Y. lipolytica var. alkalitolerance. The ecophysiological properties and biotechnological potentials of the new strain are discussed.

Properties of the cysteine-less Pho84 phosphate transporter of Saccharomyces cerevisiae.

The derepressible Pho84 high-affinity phosphate permease of Saccharomyces cerevisiae, encoded by the PHO84 gene belongs to a family of phosphate:proton symporters (PHS). The protein contains 12 native cysteine residues of which five are predicted to be located in putative transmembrane regions III, VI, VIII, IX, and X, and the remaining seven in the hydrophilic domains of the protein. Here we report on the construction of a Pho84 transporter devoid of cysteine residues (C-less) in which all 12 native residues were replaced with serines using PCR mutagenesis and the functional consequences of this. Our results clearly demonstrate that the C-less Pho84 variant is able to support growth of yeast cells to the same extent as the wild-type Pho84 and is stably expressed under derepressible conditions and is fully active in proton-coupled phosphate transport across the yeast plasma membrane.