Inactivation of Escherichia coli in soil by solarization

Contamination of agricultural soil by fecal pathogenic bacteria poses a potential risk of infection to humans. For the biosafety control of field soil, soil solarization in an upland field was examined to determine the efficiency of solarization on the inactivation of Escherichia coli inoculated into soil as a model microorganism for human pathogenic bacteria. Soil solarization, carried out by sprinkling water and covering the soil surface with thin plastic sheets, greatly increased the soil temperature. The daily average temperature of the solarized soil was 4–10°C higher than that of the non-solarized soil and fluctuated between 31 and 38°C. The daily highest temperature reached more than 40°C for 8 days in total in the solarized soil during the second and third weeks of the experiment. Escherichia coli in the solarized soil became undetectable (< 0.08 c.f.u. g⁻¹ dry soil) within 4 weeks as a result, whereas E. coli survived for more than 6 weeks in the non-solarized soil. Soil solarization, however, had little influence on the total direct count and total viable count of bacteria in the soil. These results indicate that soil solarization would be useful for the biosafety control of soil contaminated by human pathogens via immature compost or animal feces.     

Heavy-ion-induced mutants in sweet pepper isolated by M1 plant selection

We examined the effects of heavy-ion bombardment on mutagenesis in sweet pepper (Capsicum annuum L.). Dose–response studies indicated that 10 Gy irradiation of ¹²C or ²⁰Ne ions on dry seeds is suitable for inducing mutations in plants. From ²⁰Ne-irradiated M₁ plants, putative mutants included two dwarf plants and one plant whose pericarp was yellow were isolated. Phenotypes of their M₂ progeny were similar to those of the M₁ plants and did not segregate. F₁ plants resulting from reciprocal crosses between the mutants and wild-type plants showed the wild-type phenotype, but phenotypes of F₂ and BC₁F₁ segregated at 1:3 (mutant:wild) and 1:1, respectively. These crossing experiments indicate that the three mutants have monogenic recessive mutations in nuclear genes. In light of these data, we discuss the effectiveness of using heavy-ion bombardment to mutate sweet peppers.     

Methionine sulfoximine suppressed the stimulation of dark carbon fixation by ammonium nutrition in wheat roots

To evaluate the role of NH₄ ⁺ assimilates in dark carbon fixation in roots in providing carbon skeletons expended for NH₄ ⁺ assimilation, the rate of dark carbon fixation in roots was measured using NaH¹⁴CO₃. The ¹⁴C-metabolites were analyzed in wheat (Triticum aestivum L.) plants grown in NH₄ ⁺ media for various periods of time with or without methionine sulfoximine (MSX) treatment. The dark carbon fixation rate in the roots of wheat plants that had been grown with NH₄ ⁺ for 1 d was approximately 6-fold higher than the rate in control roots. The stimulation of dark carbon fixation in NH₄ ⁺-grown plants, however, was not observed in MSX-treated roots. In the roots of NH₄ ⁺-grown plants, the concentration and ¹⁴C-Iabeling of acidic metabolites such as citrate and malate considerably decreased whereas those of basic metabolites, especially asparagine, increased noticeably. With MSX treatment, the incorporation of ¹⁴C into basic metabolites was negligible. In response to NH₄ ⁺, phosphoenolpyruvate carboxylase (PEPC) activity increased, and PEPC proteins accumulated in wheat roots. Neither activity nor amounts of PEPC in roots increased in the presence of MSX. These findings suggest that primary assimilation of NH₄ ⁺ in roots is essential for the stimulation of dark carbon fixation, which coincides with the increased activity of root PEPC, to sufficiently replenish carbon skeletons necessary for NH₄ ⁺ assimilation.     

Tillage,fertilizer type,and plant residue input impacts on soil carbon sequestration rates on a Japanese Andosol

ABSTRACT

To identify efficient field management practices for enhanced soil carbon sequestration suited to crop rotation-based Andosol fields in northern Japan, the impacts of a combination of tillage, fertilizer type, and plant residue input on soil carbon sequestration rates were studied in a 4-year field experiment (April 2007 to March 2011). The rates of changes in soil organic carbon over the entire study period were determined by soil carbon stock change and by net ecosystem carbon budget. Across eight field management treatments and two replicates for each treatment, the rates of changes in soil organic carbon determined by net ecosystem carbon budget were positively correlated with the rates determined by soil carbon stock change (r = 0.766, n = 16). The arithmetic means of the rates determined by net ecosystem carbon budget (1.24 Mg C ha^?1 year^?1) were greater than those determined by soil carbon stock change (?0.18 Mg C ha^?1 year^?1) because decomposing crop residues and composted cattle manure in soil were included in the calculation of the net ecosystem carbon budget but were excluded in the calculation of soil carbon stock change (decomposing crop residues and composted cattle manure in soil samples were removed by sieving in measuring the soil carbon stock change). Both methods led to the same conclusion that soil carbon sequestration was significantly enhanced by composted cattle manure application and increased input of plant carbon from crop residues and green manure but was not enhanced by reduced tillage. The p values for net ecosystem carbon budget were smaller than those for soil carbon stock change in analysis of variance; therefore, the net ecosystem carbon budget was more sensitive to field management practice than the soil carbon stock change.     

Advantages of a diluted nutrient broth medium for isolating N2-producing denitrifying bacteria of α-Proteobacteria in surface and subsurface upland soils

This research aimed to determine whether a diluted nutrient broth (DNB) medium was different from a conventional nutrient broth (NB) medium when counting and isolating denitrifying bacteria in surface and subsurface upland soils. To this end, we investigated populations of denitrifying bacteria isolated from the surface to a depth of 4 m of subsurface upland soil that had received slurry. The DNB medium gave higher viable counts of denitrifying bacteria than the NB medium and a higher isolation ratio of denitrifying bacterial isolates. In total, 74 isolates from the DNB medium (D-isolates) and 26 isolates from the NB medium (N-isolates) were collected. We characterized their denitrifying activity and analyzed the diversity of 16S rDNA and denitrifying-related genes. Seventy-three percent of the D-isolates were oligotrophic denitrifying bacteria. The N₂-producing, oligotrophic denitrifying bacteria, largely of α-Proteobacteria, increased in the D-isolates. The D-isolates and the N-isolates had some taxonomic overlapping on a phylogenetic tree based on 16S rDNA. It was not possible to identify the denitrification phenotype (N₂-producing or N₂O-producing) on the phylogenetic tree. Phylogenetic groups of isolates corresponded to nirK groups, except in some isolates in which horizontal gene transfer might have occurred. The terminal gas emission of the isolates was consistent with the existence of the nosZ gene. The DNB medium may be very useful in isolating N₂-producing denitrifying α-Proteobacteria. Its use highlights the ecological significance of oligotrophic isolates and the different viable counts resulting from the selectivity of conventional and diluted media.     

Development of an in vitro model for the analysis of bovine endometrium using simple techniques

This study aimed to develop an in vitro model for the analysis of the bovine endometrium. Immunofluorescent staining revealed that the hetero‐spheroids and the cultured explants showed almost similar structure in the localization of bovine endometrial epithelial cells and endometrial stromal cells, except the glandular‐like structure of the epithelial cells inside the explants. Gelatin zymography revealed that the hetero‐spheroids did not express matrix metalloproteinases (MMPs) after 4 days of culture, but strong MMP expressions were observed in the cultured explants until 7 days of culture. Additionally, expression of progesterone receptor (PR), estrogen receptor alpha (ERα), type I interferon receptor 1 (IFNAR1) and 2 (IFNAR2) messenger RNA was observed both in the homo‐ and hetero‐spheroids. The expression of oxytocin receptor (OTR) mRNA in E2 and E2+P4 (1,3,5(10)‐Estratrien‐3, 17β‐diol + 4‐Pregnen‐3, 20‐dinone) treated groups were significantly (P < 0.05) higher than that of the control group of spheroids. In case of cultured explants, the expression of PR and OTR mRNA were significantly (P < 0.05) higher in E2 treated groups compared to the control groups. Hepatocyte growth factor (HGF) mRNA expression was also higher in P4 treated groups at 10 days in culture (P < 0.05). In a nutshell, the in vitro model developed in this study for the analysis of the endometrium may provide a new platform for extensive research on bovine endometrial function.     

NMR-based screening method for transglutaminases: rapid analysis of their substrate specificities and reaction rates

Incorporation of inter- or intramolecular covalent cross-links into food proteins with microbial transglutaminase (MTG) improves the physical and textural properties of many food proteins such as tofu, boiled fish paste, and sausage. Other transglutaminases (TGases) are expected to be used in the same way, and also to extend the scope of industrial applications to materials, drugs, and so on. The TGases have great diversity, not only in amino acid sequence and size, but also in their substrate specificities and catalytic activities, and therefore, it is quite difficult to estimate their reactivity. We have developed an NMR-based method using the enzymatic labeling technique (ELT) for simultaneous analysis of the substrate specificities and reaction rates of TGases. It is quite useful for comparing the existing TGases and for screening new TGases or TGases variants. This method has shown that MTG is superior for industrial use because of its lower substrate specificity compared with those of guinea pig liver transglutaminase (GTG) and red sea bream liver transglutaminase (FTG). We have also found that an MTG variant lacking an N-terminal aspartic acid residue has higher activity than that of the native enzyme.     

Water resistance properties of kenaf core binderless boards

Abstract Binderless boards were prepared from kenaf core under various manufacturing conditions and their water resistance properties were evaluated. The board properties evaluated were retention ratios of modulus of rupture (MOR) and modulus of elasticity (MOE), internal bonding strength after water treatment (IB), thickness swelling (TS), water absorption (WA), and linear expansion (LE). These values were then compared with those of boards bonded with urea-formaldehyde (UF), urea melamine formaldehyde (UMF), and phenol-formaldehyde (PF) resins, and their water resistance properties were assessed. We found that pressing temperature was one of the most important conditions for the improvement of water resistance properties. The retention ratios of MOR, MOE, and IB of kenaf core chip binderless boards (pressing temperature 200°C, target density 0.8g/cm³, and the three-step pressing of 6MPa for 10min, then 4MPa for 3min, and 2MPa for 3min) were 37.1%, 49.9%, and 55.7%, respectively, compared with values for UMF-bonded boards of 22.5%, 27.1%, and 40.7%, and values for PF-bonded boards of 42.8%, 41.8%, and 54.1%, respectively. The results showed that the water resistance properties of binderless boards were higher than those of UMF-bonded boards and almost as high as those of PF-bonded boards. Part of this article was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, March 2003