[Screening of extreme salt-alkali tolerant strain and effect of its fertilizer on wheat growth and soil environment under saline-alkali condition.] / æžç«¯è€ç›ç¢±èŒæ ªçš„ç­›é€‰åŠå ¶èŒè‚¥å¯¹ç›ç¢±æ¡ä»¶ä¸‹å°éº¦ç”Ÿé•¿å’ŒåœŸå£¤çŽ¯å¢ƒçš„å½±å“.

To obtain salt-alkali tolerant strains which could be potenially used to improve the quality of saline-alkali soil, soil samples collected from Dongying, Shandong Province were diluted and spread to modified Gibbson medium with pH 9 and salt concentration of 100 g·L-1. A total of 18 bacteria strains were obtained. By increasing salt concentration and pH, an extremely salt-alkali tole-rant strain N14 was screened which could grow at pH 12 and salt concentration of 20%. We analyzed the morphological, physiological and biochemical characters and 16S rDNA sequence of N14. The strain N14 was identified as Bacillus marmarensis. N14 bacterial fertilizer significantly increased the biomass of wheat, improved shoot height, fresh weight and dry weight by 21.8%, 57.9% and 41.7%, respectively. The addition of N14 bacterial fertilizer significantly increased the chlorophyll a, chlorophyll b and total chlorophyll in wheat by 36.4%, 20.0% and 31.7%, respectively. It significantly increased the activities of invertase, urease and alkaline phosphatase in saline-alkali soil by 23.2%, 68.8% and 106.5%, respectively. It also significantly increased the activities of superoxide dismutase, peroxidase and catalase in roots by 109.6%, 17.8% and 50%, respectively. The concentration of malondialdehyde in wheat roots was significantly reduced by 39.8%. This study provided an idea for the application of extreme salt-alkali tolerant bacteria and a way for improvement of saline-alkali soil.

Effects of antagonistic bacteria B6 against the pathogens of apple replant disease on the biomass of Malus hupehensis Rehd seedlings and soil environment under replanting.

We isolated strains from the rhizosphere soil of apple trees with replanting disease and evaluated the biological control potential for the pathogens Fusarium proliferatum, F. moniliforme, F. oxysporum, and F. solani. The morphological, physiological and biochemical character, and 16S rDNA sequence of the strain with the highest inhibitory rate were analyzed. The effect of strain biofertilizer on the biomass of Malus hupehensis Rehd. seedlings and soil environment under replanting disease was evaluated in a pot experiment. The results showed that the strain B6 had the strongest antagonistic activity. The inhibitory rate of B6 for F. proliferatum, F. moniliforme, F. oxysporum, Fusarium solani reached 71.8%, 70.1%, 72.6% and 91.5%, respectively. The strain B6 was identified as Bacillus methylotrophicus according to the results of morphological, physiological and biochemical character and 16S rDNA sequence analysis. Compared with the control, the bacterial manure made from the strain B6 enhanced the biomass of Malus hupehensis Rehd. seedlings in replanting soil to different extent. The ground diameter, fresh and dry mass were significantly increased by 18.3%, 49.6% and 51.2%, respectively. The strain B6 dramatically increased the number of cultivable bacteria and actinomyces in replanting soil and reduced the abundance of fungus to 37.7%, which accelerated the conversion of fungal soil to bacterial soil. It also dramatically increased the activities of sucrase, phosphatase, ureaseandcatalase in soil by 37.3%, 24.0%, 42.9% and 49.4%, respectively. In conclusion, the B6 fertilizer could improve the structure of cultivable microbial communities in the continuous cropping soil of apple trees, increase the soil enzyme activity, and enhance the growth of Malus hupehensis seedlings.

Screening of bacteria that antagonize the main pathogen fungi of apple replantation disorders from anaerobic fermented fluid of organic material and its inhibitory effect.

Anaerobic fermented organic materials fluid (AFOF) could alleviate apple replant diseases. In this study, bacteria from AFOF was screened which could antagonize the main pathogenic fungi (Fusarium solani, F. proliferatum, F. oxysporum, F. moniliforme). The effects of the antagonistic bacteria were verified by pot experiment. The results showed that AFOF could significantly inhibit the pathogenic fungi growth and reproduction. Four strains (L11, L12, L13, L14) with strong inhibition activity were obtained from AFOF by the confrontation test, with the highest inhibitory rate being up to 57.3%. All the four strains were Bacillus, with no obvious antagonism each other. Both antagonistic bacteria and methyl bromide fumigation could promote the biomass of Malus hupenhensis seedling compared with continuous cropping soil. Methyl bromide fumigation led to the best growth of M. hupenhensis seedling. The antagonistic bacteria cloud improve root activity, with root length and root tip number increased by 25.1% and 70.9%, respectively. Compared with the continuous cropping soil, antagonistic bacteria and methyl bromide fumigation effectively decreased soil fungi by 71.2% and 64.2%, respectively. Treatment with antagonistic bacteria increased soil bacteria and soil actinomycetes by 48.0% and 140.2%, respectively, indicating that soil microbial community was transformed to "bacteriatype". Treatment with methyl bromide fumigation could significantly reduce soil bacteria and soil actinomycetes, suggesting the antagonistic bacteria could inhibit the growth of pathogenic fungi in soil.

Cloning, expression and stress-respondent transcription of long-chain acyl-coenzyme A synthetase cDNA gene of Nannochloropsis gaditana and its involvement in the biosynthesis of eicosapentaenoic and decosahexaenoic acids.

A novel cDNA gene, NgLACS, that encodes a long-chain acyl-CoA sythetase (LACS), was cloned from Nannochloropsis gaditana and characterized. The cDNA was 2,360 bp in length, consisting of an ORF of 1,950 bp, a 5'-untranslated region of 88 bp and a 3'-untranslated region of 322 bp. The deduced amino acid sequence of LACS was 649 amino acid residues in length with a predicted molecular weight of 71 kDa and an isoelectric point of pH 7.8. When the alga was treated with excessive nitrogen and iron, and at 15 °C, the proportion of long-chain polyunsaturated acyl-CoAs in the total acyl-CoAs and the abundance of NgLACS cDNA gene transcript were up-regulated. Over-expression of NgLACS in Saccharomyces cerevisiae caused the accumulation of eicosapentaenoic acid and docosahexaenoic acid.

Response surface optimization of fermentation conditions for producing xylanase by Aspergillus niger SL-05.

Fermentation conditions were statistically optimized for producing extracellular xylanase by Aspergillus niger SL-05 using apple pomace and cotton seed meal. The primary study shows that culture medium with a 1:1 ratio of apple pomace and cotton seed meal (carbon and nitrogen sources) yielded maximal xylanase activity. Three significant factors influencing xylanase production were identified as urea, KH(2)PO(4), and initial moisture content using Plackett-Burman design study. The effects of these three factors were further investigated using a design of rotation-regression-orthogonal combination. The optimized conditions by response surface analysis were 2.5% Urea, 0.09% KH(2)PO(4), and 62% initial moisture content. The analysis of variance indicated that the established model was significant (P < 0.05), "while" or "and" the lack of fit was not significant. Under the optimized conditions, the model predicted 4,998 IU/g dry content, whereas validation experiments produced an enzymatic activity of xylanase at 5,662 IU/g dry content after 60 h fermentation. This study innovatively developed a fermentation medium and process to utilize inexpensive agro-industrial wastes to produce a high yield of xylanase.