Growth release and growth inhibition of Pinus tabulaeformis forest in the Loess Plateau of western Shanxi Province,China北大核心CSCD

There has been increased focus on the impacts of climate change on vegetation growth, and human activities that interfere with the vegetation. Discussing the effects of climate change and thinning activity on forest growth is essential to expand plantation areas. In this study, the dendroecological method was used to analyze the radial growth of Pinus tabulaeformis to reveal the impacts of climate change and human activities on forest stand growth. These samples were derived from three different density areas of P. tabulaeformis forest at the Linfen City of Shanxi Province (the east of Loess Plateau). The correlation analysis between tree ring width index and climatic factors indicated that the growth of P. tabulaeformis was negatively related to precipitation in January and the monthly maximum temperature in December of the previous year, whereas positively correlated with precipitation in July and the monthly maximum temperature in October in that year. The phenomena of growth release and inhibition could be attributed to the impacts of climate change and thinning during 1978-2003. However, growth inhibition was closely related to unsuitable climatic conditions. Plot 1 showed a moderate growth inhibition period when the growth variation was less than -50%, and growth release was caused by thinning. The growth variation was greater than 47% in the period of growth release. Moreover, a slight growth release occurred due to tending in plot 2, and the rate of growth change exceeded 39%. A slight growth suppression induced by uncomfortable climatic condition caused growth variation less than -32% and a moderate growth release by the interaction of cutting and comfortable counterpart made variation rate larger than 75% in plot 3. The release effects of thinning can last for about 5 years. In summary, inappropriate climatic conditions can inhibit the growth of trees, and thinning can promote tree growth by about 5 years. The results can provide a reference for local forest management. © 2018 Science Press. All rights reserved.     

Chemical composition of the mycelium of Daldinia eschscholtzii北大核心CSCD

To investigate the chemical composition of the fungus Daldinia eschscholtzii, the compounds were separated by silica gel, Sephadex LH-20, and preparative chromatography. Their structures were identified by spectral methods. The MTT method was applied to measure the cytotoxicity of representative components. Eleven compounds were isolated and identified as 3β-hydroxyl-6,22-dien-5α,8α-peroxynitrite (1); ergosterol-9(11)-dehydroperoxide (2); mangiferonic acid (3); ergosta-4,6,8 (14),22-tetraen-3-one (4); (+)-syringaresinol (5); 3,5,3',5'-tetramethoxy-4,4,-diphenol (6); 5-methoxycoumarin (7); 5-hydroxy-2-methyl-4H-chromen-4-one (8); (2R,4R)-3,4-dihydro-5-methoxy-2-methyl-2H-1-benzopyran-4-ol (9); 2,3-dihydro-5-methoxy-2-methylchromen-4-one (10); and 7β-caruilignan C (11), respectively. Compound 4 showed inhibitory activity against H1299, H460, HGC-27, A5491, and MNK-45, with the IC50 value of 25.2 ± 2.9, 32.3 ± 4.2, 29.2 ± 1.2, 33.9 ± 3.7, and 18.0 ± 7.0 μmol/L, respectively. © 2018 Science Press. All rights reserved.     

Comparison of three culture methods for Cladophora oligoclona北大核心CSCD

The growth of Cladophora spp. is vigorous in the field, but not good under indoor culture conditions. In order to promote the study on ecology, water environment treatment characteristics, and the development and utilization of Cladophora, the effects of three different culture methods (standing, ventilating, water flowing + ventilating) on biomass, morphology, and photosynthetic activity of C. oligoclona were compared in order to find a suitable method for its indoor culture. The results showed that the culture method of water flowing + ventilating could effectively promote C. oligoclona biomass accumulation; the morphologies in the three culture methods were different. C. oligoclona with increased single cell length and reduced cell diameter was found in the culture method involving water flowing + ventilating; in this method, the length of the main branch and branch of the cell, plant height, and branch length of C. oligoclona were significantly higher than that in the standing and ventilating culture methods (P < 0.05). C. oligoclona cultured in the water flowing + ventilating method also showed a higher photosynthetic activity. In conclusion, among the three culture methods, the water flowing + ventilating culture method is the most suitable for the indoor culturing of C. oligoclona; this method can also provide a technical reference for the further indoor mass culture of C. oligoclona. © 2018 Science Press. All rights reserved.     

Inhibitory kinetics of β-N-acetyl-D-glucosaminidase from Nile tilapia (Oreochromis niloticus) by cadmium北大核心CSCD

Cadmium (Cd2+) pollution in an aquatic environment can negatively affect certain reproductive parameters of aquatic animals. β-N-acetyl-D-glucosaminidase (NAGase) is considered to play an important role in the fertilization process. The aim of the present study was to investigate the effect of Cd2+ on the activity of NAGase purified f rom the testis of Nile tilapia, toward contributing new knowledge on the breadth of negative effects of Cd2+ for Nile tilapia production. The kinetic method of substrate reaction was used for this assessment, and an inhibitory model was established to study the kinetics of NAGase under inhibition by Cd2+. The results showed that Cd2+ could reversibly inhibit the enzymatic activity of NAGase, and the half-maximal inhibitory concentration was estimated to be 40.95 mmol/L. Cd2+ was found to be a competitive inhibitor of NAGase, and the inhibitory constant was determined to be 17.13 mmol/L. The microscopic rate constants of inactivation were also determined. Together, these findings demonstrate that Cd2+ is a reversible inhibitor that can competitively inhibit NAGase. These results may provide a theoretical foundation for further studies on the reproduction of tilapia. © 2018 Science Press. All rights reserved.     

A new efficient azo dye-decolorizing bacterium Paenibacillus dendritiformis GGJ7 and its decolorization process北大核心CSCD

This paper aimed to find an efficient bacterium for decolorizing azo dyes. A strain which could decolorize Congo Red efficiently was isolated from Congo Red. The strain was identified as Paenibacillus dendritiformis GGJ7 (GGJ7, in short) by 16S rRNA gene sequence (NCBI accession No. KY655213). Strain GGJ7 was applied to the decolorization of azo dyes in this research, and influencing factors of decolorization were investigated, including diverse nutritional conditions, culture conditions (pH, temperature, oxygen conditions), and various dyes. The results demonstrated that the decolorization rate of Congo Red by strain GGJ7 was much higher than that of the other eight strains (e.g., YRJ1, YRJ2 etc.) in our previous work. The optimal conditions for Congo Red decolorization were 25 g/L LB broth as nutrient source, 30 °C, pH 7, and an anaerobic environment. The mechanism of decolorization was mainly biodegradation, and the decolorization process of strain GGJ7 was conformed to the first-class kinetics model: -ln (At /A0) = 0.6058t - 0.1082. For different azo dyes, the decolorization rate was up to 95%. Strain GGJ7 only needed 1 h to decolorize 50 mg/L Methyl Orange, 25 mg/L Croceine Scarlet, and 25 mg/L Methyl Red, needed 3 h to decolorize 50 mg/L Orange G and 50 mg/L Orange G6, and needed 4 h to decolorize 50 mg/L Congo Red. In summary, strain GGJ7 is an efficient azo dye-decolorizing bacterium, and it has a potential application in treating printing and dyeing wastewater. © 2018 Science Press. All rights reserved.     

Microorganisms and physico-chemical properties of soils with different slope-protecting vegetation in Daguang Highway北大核心CSCD

In order to investigate the effect of different slope-protecting vegetation on soil restoration in the highways, we collected soils at depths of 0-10 cm, 10-20 cm, and 20-30 cm from areas planted with Amorpha fruticosa, Periploca sepium, and Paederia scandens for 6-7 years in the Daming road section of the Daguang Highway, in October 2016. The physico-chemical properties and microbial community of the soils were then analyzed. The soil microbial community was analyzed by terminal restriction fragment length polymorphism (T-RFLP). The correlation between the microbial community and the physico-chemical properties of the soils was determined by redundancy analysis (RDA). The results showed that (1) the physico-chemical properties were the best for soils with Paederia scandens; the nutrient content, water holding capacity, and porosity of the soils with the three types of slope-protecting vegetation were better in the 0-10 cm layer than in the other layers; (2) the contents of soil aggregates (diameter > 5 mm) were the highest in the 0-10 cm and 10-20 cm layers for the soil with Paederia scandens; (3) the dominant bacteria in the 0-10 cm layer and dominant fungi in the 0-10 cm, 10-20 cm, and 20-30 cm layers were higher in the soils with Pe. sepium and Pa. scandens than in the soil with A. fruticosa; and (4) results of RDA showed that the physical properties of the soils were the main factors that influenced the soil microbial community. The physical properties of the soils were sensitive to the change of soil quality. Soil quality can be improved by appropriate management measures, such as burying litter, which can subsequently improve the ecological environment of soils in sloping regions. © 2018 Science Press. All rights reserved.     

The oligopeptides production by the feather-degrading bacterium Bacillus methylotrophicus H0北大核心CSCD

Due to the high nutritive value of oligopeptides and the waste of feather resources, this study aimed at screening efficient strains of bacteria able to rapidly degrade feathers and produce large quantities of value-added oligopeptides. In order to assess the potential yield of oligopeptides, the promising strain H0 was selected from 16 feather-degrading microorganisms. To identify the strain, we analyzed the morphological and physiological characteristics of different strains, and carried out a gene sequence analysis of their 16S rRNAs. A single factor experiment was used to promote feather degradation and oligopeptide production, and the characteristics of the oligopeptides produced were also analyzed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). The strain was identified as Bacillus methylotrophicus. The optimal initial pH and temperature for oligopeptide production were 11 and 40 °C, respectively. After 72 h of fermentation under these optimal conditions, the feathers were almost completely degraded, with a 38.19% of oligopeptides (accounting for 67.53% of the total soluble peptides) and a 11.11% of free amino acids produced. LC-MS/MS analysis indicated that the oligopeptides were mainly short peptides containing 5-10 amino acids, with a molecular mass (Mr) of less than 1 300. Moreover, the peptides were abundant in branched-chain amino acids, that might be responsible for the antioxidant property of the feather hydrolysate. Our results demonstrate the great capability of B. methylotrophicus H0 in feather degradation and oligopeptide production. This research provides a high-quality microorganism resource, and the scientific basis for the development of feather-derived oligopeptide products. © 2018 Science Press. All rights reserved.