Phosphorus availability may shape plantmicroorganism-soil interactions in forest ecosystems. Our aim was to quantify the interactions between soil P availability and P nutrition strategies of European beech (Fagus sylvatica) forests. We assumed that plants and microorganisms of P-rich forests carry over mineral-bound P into the biogeochemical P cycle (acquiring strategy). In contrast, P-poor ecosystems establish tight P cycles to sustain their P demand (recycling strategy). We tested if this conceptual model on supply-controlled P nutrition strategies was consistent with data from five European beech forest ecosystems with different parent materials (geosequence), covering a wide range of total soil P stocks (160-900 g P m -2 ; \1 m depth). We analyzed numerous soil chemical and biological properties. Especially P-rich beech ecosystems accumulated P in topsoil horizons in moderately labile forms. Forest floor turnover rates decreased with decreasing total P stocks (from 1/5 to 1/40 per year) while ratios between organic carbon and organic phosphorus (C:P org ) increased from 110 to 984 (A horizons). High proportions of fine-root biomass in forest floors seemed to favor tight P recycling. Phosphorus in fine-root biomass increased relative to microbial P with decreasing P stocks. Concomitantly, phosphodiesterase activity decreased, which might explain increasing proportions of diester-P remaining in the soil organic matter. With decreasing P supply indicator values for P acquisition decreased and those for recycling increased, implying adjustment of plantmicroorganism-soil feedbacks to soil P availability. Intense recycling improves the P use efficiency of beech forests.

The anionic ring-opening polymerization of alkylene oxides, except ethylene oxide, is accompanied by strong side reactions, leading to high molecular weight and low molecular weight byproducts. In this work we investigated the anionic polymerization of hydrophobic alkylene oxides at different temperatures, solvents, and initiating systems. For polymers synthesized in the temperature range between 40 and 80 °C and employing potassium and cesium alcoholate initiators significant amounts of byproducts were found. With the help of crown ethers the temperature could be reduced to −23 °C without extending polymerization times too much. This measure allowed eliminating byproducts almost completely. The best results were obtained with potassium alcoholates and 18-crown-6 in toluene at −10 to −23 °C. Poly(1,2-butylene oxide), poly(1,2-hexylene oxide), and poly(1,2-octylene oxide) homopolymers were synthesized up to molecular weights in the range of 50 000−100 000 and M w/M n < 1.1. Furthermore, the method was employed to synthesize amphiphilic block copolymers of the hydrophobic poly(alkylene oxide)s with poly(ethylene oxide) as the hydrophilic moiety. Block molecular weights reached up to 50 000. Even at those high molecular weights the contents of homopolymer byproduct did not exceed 1%. The results indicate that side reactions usually involved in the anionic polymerization of alkylene oxides were largely suppressed using the employed polymerization technique.

Corynebacterium glutamicum is able to accumulate up to 600 mM cytosolic phosphorus in the form of polyphosphate (poly P). Granular poly P (volutin) can make up to 37% of the internal cell volume. This bacterium lacks the classic enzyme of poly P synthesis, class I polyphosphate kinase (PPK1), but it possesses two genes, ppk2A (corresponds to NCgl0880) and ppk2B (corresponds to NCgl2620), for putative class II (PPK2) PPKs. Deletion of ppk2B decreased PPK activity and cellular poly P content, while overexpression of ppk2B increased both PPK activity and cellular poly P content. Neither deletion nor overexpression of ppk2A changed specific activity of PPK or cellular poly P content significantly. Purified PPK2B of C. glutamicum is active as a homotetramer and formed poly P with an average chain length of about 125, as determined with 31 P nuclear magnetic resonance. The catalytic efficiency of C. glutamicum PPK2B was higher in the poly P-forming direction than for nucleoside triphosphate formation from poly P. The ppk2B deletion mutant, which accumulated very little poly P and grew as C. glutamicum wild type under phosphate-sufficient conditions, showed a growth defect under phosphate-limiting conditions.Inorganic polyphosphate (poly P), a linear polymer consisting of three to hundreds of orthophosphate residues linked by phosphoanhydride bonds (20, 37), has been found in all living cells examined: archaea, bacteria, and eukarya (7,20,37). Poly P is synthesized by polyphosphate kinases (PPKs), using the terminal phosphate of ATP as the substrate, and is degraded to inorganic phosphate (P i ) by both endo-and exopolyphosphatases (19,20,37). Among the many functions poly P performs, the most prominent are the responses to many stresses. A variety of defects in responses to environmental stresses and/or virulence were observed in PPK gene mutants of Escherichia coli, Pseudomonas aeruginosa, Shigella, Salmonella, Vibrio cholerae, and Helicobacter pylori (5,14,17,32). In E. coli, it could be demonstrated that under conditions of amino acid starvation, poly P accumulates and is bound by Lon protease (21). The Lon-poly P complex degrades ribosomal proteins supplying amino acids in response to starvation (21).PPKs, which can be grouped into two classes, catalyze the reversible transfer of the gamma phosphoryl group of ATP or GTP to poly P. Genetic and biochemical studies have established the role of PPKs for biosynthesis of poly P, e.g., in the gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa (2, 3, 44). The archetypes of PPKs are class I PPK, PPK1, from E. coli, and class II PPK, PPK2, from P. aeruginosa. PPK2 of P. aeruginosa differs from ATP-specific PPK1, as it accepts GTP as well as ATP (12). Moreover, while the rate of GTP synthesis catalyzed by P. aeruginosa PPK2 is 75-fold higher than the rate of poly P synthesis, E. coli PPK1 shows a preference for poly P synthesis (12). Based on the presence or absence of PPK1 and/or PPK2 genes within complete genome sequences, Zhang et al. (44) distinguished fo...

Due to the limited solubility of phosphorus (P) in soil, understanding its binding in fine colloids is vital to better forecast P dynamics and losses in agricultural systems. We hypothesized that water-dispersible P is present as nanoparticles and that iron (Fe) plays a crucial role for P binding to these nanoparticles. To test this, we isolated water-dispersible fine colloids (WDFC) from an arable topsoil (Haplic Luvisol, Germany) and assessed colloidal P forms after asymmetric flow field-flow fractionation coupled with ultraviolet and an inductively coupled plasma mass spectrometer, with and without removal of amorphous and crystalline Fe oxides using oxalate and dithionite, respectively. We found that fine colloidal P was present in two dominant sizes: (i) in associations of organic matter and amorphous Fe (Al) oxides in nanoparticles <20 nm, and (ii) in aggregates of fine clay, organic matter and Fe oxides (more crystalline Fe oxides) with a mean diameter of 170 to 225 nm. Solution P-nuclear magnetic resonance spectra indicated that the organically bound P predominantly comprised orthophosphate-monoesters. Approximately 65% of P in the WDFC was liberated after the removal of Fe oxides (especially amorphous Fe oxides). The remaining P was bound to larger-sized WDFC particles and Fe bearing phyllosilicate minerals. Intriguingly, the removal of Fe by dithionite resulted in a disaggregation of the nanoparticles, evident in higher portions of organically bound P in the <20 nm nanoparticle fraction, and a widening of size distribution pattern in larger-sized WDFC fraction. We conclude that the crystalline Fe oxides contributed to soil P sequestration by (i) acting as cementing agents contributing to soil fine colloid aggregation, and (ii) binding not only inorganic but also organic P in larger soil WDFC particles.

Inorganic polyphosphate (polyP) is the polymer of orthophosphate and can be found in all living organisms. For polyP characterization, one or more of six parameters are of interest: the molecular structure (linear, cyclic, or branched), the concentration, the average chain length, the chain length distribution, the cellular localization, and the cation composition. Here, the merits, limitations, and critical parameters of the state-of-the-art methods for the analysis of the six parameters from the life sciences are discussed. With this contribution, we aim to lower the entry barrier into the analytics of polyP, a molecule with prominent, yet often incompletely understood, contributions to cellular function. See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. b Refers to absorption and fluorescence spectroscopy. Analytical Chemistry pubs.acs.org/ac Feature https://dx.

Abstract. To maximize crop productivity fertilizer P is generally applied to arable soils, a significant proportion of which becomes stabilized by mineral components and in part subsequently becomes unavailable to plants. However, little is known about the relative contributions of the different organic and inorganic P bound to Fe/Al oxides in the smaller soil particles. Alkaline (NaOH-Na 2 EDTA) extraction with solution 31 P-nuclear magnetic resonance ( 31 P-NMR) spectroscopy is considered a reliable method for extracting and quantifying organic P and (some) inorganic P. However, any so-called residual P after the alkaline extraction has remained unidentified. Therefore, in the present study, the amorphous (a) and crystalline (c) Fe/Al oxide minerals and related P in soil aggregate-sized fractions (> 20, 2-20, 0.45-2 and < 0.45 µm) were specifically extracted by oxalate (a-Fe/Al oxides) and dithionite-citrate-bicarbonate (DCB, both a-and c-Fe/Al oxides). These soil aggregate-sized fractions with and without the oxalate and DCB pre-treatments were then sequentially extracted by alkaline extraction prior to solution 31 P-NMR spectroscopy. This was done to quantify the P associated with a-and c-Fe/Al oxides in both alkaline extraction and the residual P of different soil aggregate-sized fractions.The results showed that overall P contents increased with decreasing size of the soil aggregate-sized fractions. However, the relative distribution and speciation of varying P forms were found to be independent of soil aggregate-size. The majority of alkaline-extractable P was in the a-Fe/Al oxide fraction (42-47 % of total P), most of which was orthophosphate (36-41 % of total P). Furthermore, still significant amounts of particularly monoester P were bound to these oxides. Intriguingly, however, Fe/Al oxides were not the main bonding sites for pyrophosphate. Residual P contained similar amounts of total P associated with both a-(11-15 % of total P) and c-Fe oxides (7-13 % of total P) in various aggregate-sized fractions, suggesting that it was likely occluded within the a-and c-Fe oxides in soil. This implies that, with the dissolution of Fe oxides, this P may be released and thus available for plants and microbial communities.

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Using small-angle neutron scattering, the unperturbed chain dimensions of a series of poly(alkylene oxide)s (PAO’s) were studied as a function of side-chain length. The PAO’s were obtained using anionic ring-opening polymerization methods. The deuterated monomers were synthesized from commercially available precomponents. A systematic decrease of the chain dimensions with increasing length of the side chains was found. We also compare the PAO’s with the chemically very similar poly(olefin)s with respect to the characteristic ratio C ∞, the chain dimensions, and the packing length as a function of the molecular weight per backbone bond. In doing so, we found significant differences between the static properties of the two systems.