松材线虫携带一株荧光假单胞菌分泌毒素的初步研究

本文研究了离体情况下松材线虫携带的致病菌一株荧光假单胞菌（Pseudomonas fluorescens GcM5-1A）在LB、NB和PD三种培养基中的毒性,以及产生的毒素对黑松（Pinus thunbergii）切根苗和悬浮细胞的效应。结果显示,菌体在LB和NB培养液的毒性较高,其中LB培养液的毒性最高,且培养液的pH值为7时比pH值为5时毒性高,而该菌EPD培养基中几乎不产毒。细菌培养液经硫酸铵分级沉淀,得到了主要含有50kDa蛋白的蛋白组分,该蛋白组分对黑松悬浮细胞和切根苗均有较高的毒性,并能改变黑松悬浮细胞细胞膜的透性,导致胞内可溶性糖和游离氨基酸外渗。     

荧光假单胞菌鞭毛蛋白对黑松细胞的致死作用

采用细胞免疫荧光分析、细胞染色观察、电导率测定以及基因组DNA电泳分析技术,研究了松材线虫携带的荧光假单胞菌分泌的鞭毛蛋白对黑松愈伤组织细胞的作用及其致死方式。结果表明,鞭毛蛋白与黑松细胞之间存在直接的相互作用;鞭毛蛋白处理的细胞,细胞膜皱缩变形、细胞质浓缩、细胞核解体,形成若干小核,细胞质中的RNA降解;处理细胞的着色力增强,细胞培养液的电导率增加,说明鞭毛蛋白可增加处理细胞的细胞膜透性;基因组DNA的电泳分析证实,处理细胞的DNA发生了断裂,但无明显的梯子形成,推测鞭毛蛋白对黑松细胞的致死方式为非典型的细胞凋亡。     

松材线虫的天然毒素研究进展

概述了松材线虫病的现行防治措施及存在问题,介绍了植物源和真菌源天然毒素毒杀松材线虫的研究现状及研究中遇到的问题,指出天然毒素在未来松材线虫病生物防治中的研究方向。     

沼泽红假单胞菌对微囊藻毒素的降解

以铜绿微囊藻为材料,通过固相萃取-高效液相色谱方法(SPE-HPLC),研究了沼泽红假单胞菌对微囊藻毒素MC-LR的降解作用。结果表明:沼泽红假单胞菌在厌氧、光照强度2000lx、35℃、pH7.0、乙酸钠为碳源、菌液初始浓度OD680为0.325和初始MC-LR为3mg.L-1时,6d降解率为36.5%,12d达到最高,降解率为78.7%。此降解条件和蓝藻水华爆发的环境条件基本一致,因此该菌株在水华爆发季节消除水中的微囊藻毒素方面具有应用潜力。     

荧光假单胞菌的条件致病性

作者从血、尿标本中分离出12株荧光假单胞菌,在研究生物学性状的基础上探讨了本菌的条件致病性问题,结果显示,凡能使机体免疫力下降的各种原因均可导致本菌感染。治疗本菌感染,必须进行药敏试验,选择有效的抗生素。     

丁香假单胞菌环式脂肽毒素的生理和分子生物学研究

综合评述了近１０年来在丁香假单胞菌脂肽毒素生理和分子生物学研究上的发现。这些毒素依肽部ＡＡ数目可分两组。丁香假单胞霉素组（ｓｙｒｉｎｇｏｍｙｃｕｎｓ）已报告４个成员,肽部有９个ＡＡ;丁香假单胞肽毒素组有２个成员,肽部分别有２２个和２５个ＡＡ。肽部Ｃ－端羧基与分子内羟基氨基酸残基（ＡＡ）的羟基酯化闭合成环,再由羟基脂肪酸酰化。两组毒素都诱导植物电解质渗漏、人和动物红血球溶解,其机制在于在细胞膜上形成     

一株红假单胞菌分离及对幼鳖作用的初步研究

从露天养鳖池中分离到红假单胞菌CZ-2菌株。该菌具有生理需求简单、培养条件粗放、生长迅速的特点。在黑暗,好氧和光照/厌氧条件下均可良好生长,最适条件下培养6d,生物量可以达到1．57g/L。在温室幼鳖的饲料中添加CZ-2菌株培养液后幼鳖没有出现直接死亡,发病率也较对照池低50％左右。试验表明CZ-2菌株培养液对幼鳖生长有促进作用,比对照提高了8．9％。该文对CZ-2菌株培养特性及对幼鳖作用作了探讨。     

假单胞菌降解微囊藻毒素的效能及酶作用机理

以从福州市某富营养化水库底泥中筛选出的假单胞菌M-6为研究对象,分别考察接种量、温度、供氧量(转速)、pH值、微囊藻毒素MCLR初始浓度等条件因素对假单胞菌M-6降解MCLR的影响,并探讨假单胞菌M-6降解MCLR的分子生物学机理.结果表明,当接种量为10%时,菌体的降解效果较好,6d的降解率可达90%;降解反应的最适pH为7.0,最佳温度为30℃,摇床转速控制在150 r/min;MCLR初始浓度过高都将影响假单胞菌M-6对碳源和氮源的吸收和利用,最佳浓度为15.7 mg/L.SDS-PAGE电泳分析表明,假单胞菌M-6降解藻毒素过程中,主要有3种酶参与反应,且这3种酶都是细胞内本身所含有的组织酶.     

Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.     

荧光假单胞杆菌P13菌株对油菜化感作用的研究

通过化感试验研究荧光假单胞杆菌P13菌株对油菜种子萌发、幼苗生长的影响及其在油菜根际土壤和根部定植的能力。结果表明,P13菌株发酵液对油菜种子萌发没有明显的促进作用,稀释10倍的菌体发酵液处理种子与对照组无显著差异,而低浓度和高浓度都抑制种子萌发;田间试验发现P13菌株能促进植物幼苗生长,根长、苗高、干重和长1片叶子的株数均与对照组差异显著;1周内P13菌株在油菜根际土壤和根部定植良好,定植数量均达到107cfu/g以上。说明P13菌株可被开发为微生物菌剂,但在施用时不宜用作种子处理剂。     

Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa.

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.     

Nitrite inhibition of denitrification by Pseudomonas fluorescens

Using a pure culture of Pseudomonas fluorescens as a model system nitrite inhibition of denitrification was studies. A mineral media with acetate and nitrate as sole electron donor and acceptor, respectively, was used. Results obtained in continuous stirred-tank reactors (CSTR) operated at pH values between 6.6 and 7.8 showed that growth inhibition depended only on the nitrite undissociated fraction concentration (nitrous acid). A mathematical model to describe this dependence is put forward. The maximum nitrous acid concentration compatible with cell growth and denitrification activity was found to be 66 mug N/L. Denitrification activity was partially associated with growth, as described by the Luedeking-Piret equation. However, when the freshly inoculated reactor was operated discontinuosly, nitrite accumulation caused growth uncoupling from denitrification activity. The authors suggest that these results can be interpreted considering that (a) nitrous acid acts as a proton uncoupler; and (b) cultures continuoulsy exposed to nitrous acid prevent the uncoupling effect but not the growth inhibition. Examination of the growth dependence on nitrite concentration at pH 7.0 showed that adapted cultures (grown on CSTR) are less sensitive to nitrous acid inhibition than the ones cultivated in batch. (c) 1995 John Wiley & Sons, Inc.     

Influence of Temperature on Glucose Utilization by Pseudomonas fluorescens

The influence of temperature on the conversion of glucose into cell material and into energy for maintenance was determined for Pseudomonas fluorescens by a steady-state turbidity method and by a substrate utilization method. Conversion of glucose into cell material was measured as yield; conversion of glucose into energy for maintenance was measured as specific maintenance, the minimum dilution rate in continuous culture below which a steady state is not possible. The values obtained by the two methods were nearly identical; with both, the yield and specific maintenance decreased with decreasing temperature. The specific maintenance consumption rate (milligrams of glucose taken up per milligram of cell dry weight per hour at zero growth) was also calculated by the substrate utilization method and found to decrease with decreasing temperature. However, the amount of glucose consumed per generation for maintenance increased with decreasing temperature. This increased glucose consumption for maintenance may provide a partial explanation for the decrease in yield at low temperatures. Small amounts of glucose were also converted into pigment at all temperatures tested, with the greatest amount formed at 20 C.