Effects of low‐molecular‐weight organic compounds on sulphur immobilization and re‐mineralization and extraction of immobilized sulphur by hot‐water and acid hydrolysis

We examined the effects of salicylate, glutamate and glucose on sulphur (S) immobilization and re‐mineralization in three calcareous soils: from arable, fallow and forest managements. Each of the three substrates, at a single rate of carbon (1000 mg C kg⁻¹ soil) was added to the three soils and then incubated with NaSO₄ plus Na₂SO₄ for 1, 2, 6 or 12 weeks prior to analysis. The extraction of the immobilized S was performed with either hot water (HW‐S) or 3 m hydrochloric acid (HCl‐S). Except for the forest soil, the average amounts of immobilized S increased in the order control < salicylate < glutamate < glucose. Across all soils, substrate addition significantly decreased the average value of HCl‐S expressed as a percentage of immobilized S compared with that of the control. The decreases in HCl‐S (58 − 100%) were substrate‐ and time‐independent, suggesting a heterogeneous action of HCl. In contrast, except for the forest soil, we found substantial declines in the average percentage values of HW‐S (21 − 75% of the immobilized S) in the order control > salicylate > glutamate = glucose, suggesting that the hot‐water action was substrate dependent. In addition, the proportion of HW‐S decreased with increasing incubation time, indicating that the youngest immobilized S was the most labile. Thus, hot water extracted more homogeneous S compounds than HCl. Sulphur immobilization induced by glutamate and glucose produced more recalcitrant S products (small quantities of ³⁵S re‐mineralization) than that induced by salicylate. Glutamate tended to generate more recalcitrant S compounds than glucose. Hot‐water extractable S was a valuable and rapid indicator of readily labile organic S. Consequent microbial S immobilization resulting from glucose or glutamate addition was followed by a small rate of re‐mineralization of immobilized S.     

Chromosome alignment and segregation regulated by ubiquitination of survivin

Proper chromosome segregation requires the attachment of sister kinetochores to microtubules from opposite spindle poles to form bi-oriented chromosomes on the metaphase spindle. The chromosome passenger complex containing Survivin and the kinase Aurora B regulates this process from the centromeres. We report that a de-ubiquitinating enzyme, hFAM, regulates chromosome alignment and segregation by controlling both the dynamic association of Survivin with centromeres and the proper targeting of Survivin and Aurora B to centromeres. Survivin is ubiquitinated in mitosis through both Lys(48) and Lys(63) ubiquitin linkages. Lys(63) de-ubiquitination mediated by hFAM is required for the dissociation of Survivin from centromeres, whereas Lys(63) ubiquitination mediated by the ubiquitin binding protein Ufd1 is required for the association of Survivin with centromeres. Thus, ubiquitinaton regulates dynamic protein-protein interactions and chromosome segregation independently of protein degradation.     

Measurement and modeling of Western Washington precipitation chemistry

Water, Air, & Soil Pollution - Precipitation was collected and chemically analyzed for a 1 yr period at four sites in Western Washington. Spatial and seasonal variabilities in concentrations...     

畜禽矿物质微量元素添加剂的作用

本文论述了畜禽缺乏钙、磷、钠、氯和微量元素铁、铜、钴、硒、碘时引起的各种病症，矿物质微量元素对畜禽的生理作用，指出了此类添加剂的饲喂方法和正确的使用方法。     

中草药饲料添加剂的作用与开发

中草药饲料添加剂不但能发挥促进动物生长的作用,而且能克服化学添加剂引起的动物产品中药物、激素、微量元素的超标残留.本文简述了中草药饲料添加剂的作用和功效,分析了其研发现状及趋势.     

Effects of glucose and rhizodeposits (with or without cysteine-S) on immobilized-35S, microbial biomass-35S and arylsulphatase activity in a calcareous and an acid brown soil

Our aim was to study the effects of C (as glucose and artificial rhizodeposits) on S immobilization, in relation to microbial biomass‐S and soil arylsulphatase (ARS) activity, in contrasting soils (a calcareous and an acid brown soil). The glucose‐C and artificial rhizodeposit‐C with or without cysteine were added at six rates (0, 100, 200, 400, 600 and 800 mg kg^?1 soil) to the two soils and then incubated with Na₂³⁵SO₄ for 1 week prior to analysis. The percentages of ³⁵S immobilized increased when C as glucose and rhizodeposit (without cysteine) were added to both soils. With cysteine‐containing rhizodeposit, the percentages of ³⁵S immobilized remained relatively stable (23.5% to 29.9%) in the calcareous soil, but decreased in the acid brown soil (52.7% to 31.5%). For both soils, cysteine‐containing rhizodeposit additions showed no significant correlation between immobilized‐³⁵S and microbial biomass‐³⁵S, suggesting that microorganisms immobilized cysteine‐S preferentially instead of ³⁵S from the tracer (Na₂³⁵SO₄). In the calcareous soil, a positive and significant correlation was found between ARS activity and microbial biomass‐³⁵S (r = 0.85, P < 0.05) when glucose was added. We also saw this correlation in the acid brown soil when rhizodeposit‐C without cysteine was added (r = 0.90, P < 0.05). Accordingly, the results showed the presence of extracellular arylsulphatase activity of 48.7 mg p‐nitrophenol kg^?1 soil hour^?1 in the calcareous soil and of 27.0 mg p‐nitrophenol kg^?1 soil hour^?1 in the acid brown soil.     

Immobilization of sulphur-35, microbial biomass and arylsulphatase activity in soils from field-grown rape,barley and fallow

Soils under rape, barley and fallow were monitored for S immobilization, microbial biomass and arylsulphatase (ARS) activity. These soils were regularly collected in the field every fortnight from mid-April to the end of June 2001. Then, they were incubated for 1 week at 25°C with carrier-free ³⁵S (Na₂³⁵SO₄). The results showed significant correlation of both immobilized ³⁵S ( r =0.94, P <0.001) and ARS ( r =0.79, P <0.001) with microbial biomass-³⁵S (MB-³⁵S) but not with microbial biomass-C (MB-C). Therefore, only a fraction of MB-C was involved in the immobilization of ³⁵S and hence the release of ARS. In addition, positive correlations appeared between hot water-soluble C (HW-C), ³⁵S immobilization, MB-³⁵S and ARS, indicating the pivotal role of HW-C in regulating S immobilization and turnover. The mean percentage values of immobilized ³⁵S, MB-³⁵S and ARS were higher in soil from the fallow, followed by soils from barley and rape. However, under culture, the mean values of ARS per unit of MB-³⁵S showed the decreasing order: soil from rape (0.58)>soil from barley (0.46)>soil from fallow (0.34). It is concluded that microorganisms under rape were most efficient in producing ARS, a strategy used to cope with the SO₄^2--S limiting conditions.