干旱胁迫条件下细菌多糖对玉米苗期抗旱性的影响

[目的]探究干旱胁迫条件下细菌多糖对玉米苗期抗旱性的影响。[方法]设置种子+土壤、菌液包衣种子+土壤、种子+土壤+80 ml发酵液、种子+土壤+80 ml灭活发酵液4个处理,研究不同处理对玉米苗期抗旱性的影响。[结果]玉米种子经发酵液包衣后,种子发芽率较对照可提高112.7%;对发酵液不同施用方式效果的研究表明,土壤中添加活菌液的方式对提高玉米苗期抗旱能力作用最为显著,幼苗干物质积累量、叶片中叶绿素含量、根冠比、根体积等生长指标均有显著提高,分别较对照提高130.6%、11.5%、78.1%、300.0%。[结论]该研究为有效发挥细菌多糖保水抗旱功能、开发农作物抗旱节水的新方法提供了一定的研究基础。     

Effects of the exopolysaccharide fraction (EPSF) from a cultivated Cordyceps sinensis on immunocytes of H22 tumor bearing mice

In order to explore the effects of exopolysaccharide fraction (EPSF) from one of the anamorph strains of Cordyceps sinensis on immunocyte activity of H22 tumor bearing mice, ICR mice were treated with EPSF for 7 days by intraperitoneal injection at doses of 15 mg/kg (low-dose), 30 mg/kg (mid-dose) and 60 mg/kg (high-dose) after H22 tumor cells were implanted. At the end of the experiments, the tumor weight of each mouse was measured. Phagocytosis of mouse peritoneal macrophages was tested by neutral red uptake. The TNF-alpha expression of macrophages was assayed by ELISA. Proliferation ability and cytotoxicity of spleen lymphocytes were determined by MTT methods. The mRNA levels of cytokine TNF-alpha and IFN-gamma mRNA of spleen lymphocytes were detected by RT-PCR. The results indicated that EPSF not only significantly inhibited the H22 tumor growth, but also significantly elevated immunocytes' activity. It significantly enhanced the phagocytosis capacity of peritoneal macrophages and proliferation ability of spleen lymphocytes at all the three doses; it significantly promoted macrophages' TNF-alpha expression and spleen lymphocytes' cytotoxicity. EPSF also significantly elevated TNF-alpha and IFN-gamma mRNA expression of splenic lymphocytes. This experimental finding suggests that EPSF could elevate the immunocytes' activity in H22 tumor bearing mice.     

Soil organic matter and the extracellular microbial matrix show contrasting responses to C and N availability

An emerging paradigm in soil science suggests microbes can perform ‘N mining’ from recalcitrant soil organic matter (SOM) in conditions of low N availability. However, this requires the production of extracellular structures rich in N (including enzymes and structural components) and thus defies stoichiometric expectation. We set out to extract newly synthesised peptides from the extracellular matrix in soil and compare the amino acid (AA) profiles, N incorporation and AA dynamics in response to labile inputs of contrasting C/N ratio. Glycerol was added both with and without an inorganic source of N (10% ¹⁵N labelled NH₄NO₃) to a soil already containing a large pool of refractory SOM and incubated for 10 days. The resulting total soil peptide (TSP) and extracellular pools were compared using colorimetric methods, gas chromatography, and isotope ratio mass spectrometry. N isotope compositions showed that the extracellular polymeric substance (EPS) contained a greater proportion of products formed de novo than did TSP, with hydrophobic EPS-AAs (leucine, isoleucine, phenylalanine, hydroxyproline and tyrosine) deriving substantially more N from the inorganic source provided. Quantitative comparison between extracts showed that the EPS contained greater relative proportions of alanine, glycine, proline, phenylalanine and tyrosine. The greatest increases in EPS-peptide and EPS-polysaccharide concentrations occurred at the highest C/N ratios. All EPS-AAs responded similarly to treatment whereas the responses of TSP were more complex. The results suggest that extracellular investment of N (as EPS peptides) is a microbial survival mechanism in conditions of low N/high C which, from an evolutionary perspective, must ultimately lead to the tendency for increased N returns to the microbial biomass. A conceptual model is proposed that describes the dynamics of the extracellular matrix in response to the C/N ratio of labile inputs.     

不同中药对桑黄液体深层发酵的影响

通过在桑黄液体发酵培养基中分别添加5种不同中药,研究其对桑黄菌丝生长及其代谢产物的影响。结果表明,这5种中药对桑黄菌丝生长及其代谢产物均有不同程度的影响。薏苡仁、苦荞和银杏叶在低添加量时有明显的促进作用,金银花和连翘表现出一定的抑制作用。不同中药量添加量的结果显示,薏苡仁和苦荞的最适添加量为2％,银杏叶的最适添加量为4％。     

Rhizobium sp. exopolysaccharide production,nodulation, and acetylene reduction activity (N2-fixation) in pigeon pea (Cajanus cajan L.)

Summary There was no correlation between the quantity of exopolysaccharide produced and acetylene reduction activity by Rhizobium spp. or by Bradyrhizobium spp. (Cajanus). The exopolysaccharide-defective mutants of Rhizobium sp. strain P 116 either failed to nodulate or showed a decrease in effectiveness. The deficiency in exopolysaccharide production was corrected by the addition of purified exopolysaccharide from the parent strain, or from Bradyrhizobium sp. strain P 149 or S24 isolated from pigeonpea (Cajanus cajan) and mungbean (Vigna radiata), respectively. However, the nodules so formed were not fully effective compared to those formed by the parent strain.     

Interaction of Bradyrhizobium sp. with an antagonistic actinomycete in culture medium and in soil

Summary Experiments were conducted to determine the extent to which populations of Bradyrhizobium sp. strain Tal 209SR were suppressed by the antagonistic activity of a Streptomyces sp. isolated from a highly weathered tropical soil. The activity of the actinomycete was evaluated in culture medium in the presence or absence of clay minerals and in the soil from which the actinomycete was isolated after sterilization by gamma-irradiation. The presence of the actinomycete in culture medium was associated with a significant reduction in the density of Bradyrhizobium sp. (Tal 209SR). Nevertheless, the density of the Bradyrhizobium sp. surviving in the medium in the presence of the actinomycete was much higher than that normally observed when comparable densities of rhizobia are introduced into non-sterile soils. The presence of the antagonistic actinomycete in culture medium was associated with a drastic decrease in the optical density of the medium. This decrease was accompanied by a significant decrease in the insoluble exopolysaccharide content of the medium in addition to the significant decrease in bradyrhizobial cells. The actinomycete did not appear to significantly influence the growth and survival of the test Bradyrhizobium sp. in sterile soil. The inability of the actinomycete to significantly antagonize the test bacterium in sterile soil was not adequately explained by the presence of clay minerals.Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 3129     

北冬虫夏草固体发酵产胞外多糖条件的研究

[目的]研究北冬虫夏草固体发酵产胞外多糖的条件。[方法]采用固体发酵法培养北冬虫夏草,研究碳源和氮源种类、酵母粉含量、KH2PO4含量、初始pH值、接种量、种龄及发酵时间对北冬虫夏草发酵产胞外多糖的影响。[结果]单因素试验和正交试验表明,最佳的发酵条件为:大米∶米糠=90∶10,酵母粉1.0%、KH2PO40.25%、初始pH 6.0、种龄4 d、接种量8%(V/W)、温度28℃、固水比1∶1(W/V)、发酵时间6 d。在此发酵条件下,北冬虫夏草胞外多糖产量达38.625 mg/g.干基。[结论]该研究为开发新型动物保健饲料提供了理论支持。     

干酪乳杆菌LC2W胞外多糖提取工艺研究

对影响干酪乳杆菌LC2W胞外多糖提取的主要工艺参数进行了研究。发酵液经超滤浓缩,三氯乙酸脱蛋白,乙醇沉淀等处理,得到粗多糖。单因素和正交试验结果表明,用截留分子量为10 kDa的超滤膜将发酵上清液浓缩4倍后,用终浓度6%的三氯乙酸脱蛋白,再用5倍体积95%乙醇4℃沉淀24 h,多糖提取效果较佳。在此条件下,蛋白脱除率可达88.35%,EPS提取率可达92.17%。     

姬松茸胞外多糖抗肿瘤活性研究

通过深层发酵培养姬松茸菌丝体,滤取菌丝体后获得菌丝体培养液,经沉淀离心收集其胞外粗多糖,再用蒸馏水溶解,取可溶性部分.对接种S-180的小白鼠24h后腹腔注射给药,连续10d,剂量为10 mg/kg·d.5周后剥取瘤块,与对照组比较瘤重.结果发现,姬松茸深层发酵生产的胞外多糖对小鼠接种的腹水瘤S-180有较强的抗性,肿瘤抑制率达到44.53%,完全抑制率达到50%.     

白背毛木耳43-28胞外多糖的提取与纯化

[目的]对白背毛木耳43-28胞外多糖进行提取和纯化。[方法]利用液体深层发酵进行培养,水提-醇析法分级提取胞外多糖,通过DEAE—cellulose52和SephadexG-200柱层析纯化胞外多糖。[结果]提取得到白背毛木耳43—28胞外多糖,粗多糖得率为2．4％,总糖含量为54．67％;胞外多糖粗提物经DEAE—cellulose52柱层析后分成酸性和中性多糖,这2种多糖分别经SephadexG-200柱层析后。酸性多糖分离成大分子酸性多糖AP5和小分子酸性多糖AP62个组分,中性多糖只有AW1个组分。[结论]成功提取得到白背毛木耳43-28胞外多糖并进行了纯化,为对白背毛木耳多糖的综合利用提供参考。