Colonization of Beef Muscle Surfaces by Pseudomonas fluorescens and Pseudomonas fragi

Attached and unattached cell densities were determined for Pseudomonas fluorescens and Pseudomonas fragi growing on the surface of beef muscle stored at 4 and 25°C, in presence of NaCl, KCl, and CaCl₂. A mechanical rinsing procedure was developed for this purpose. Both species colonized the surface at both temperatures and were enhanced at low (4°C) temperature. Attached cells represented up to 90% of the total until a density of 10⁵-10⁶ CFU cm^?2 was reached. At that point, a proportion of attached cells to unattached cells declined but colonization of the surface continued. In presence of CaCl₂, ratios of attached to unattached cells did not decline, suggesting a significant role for the calcium ion in colonization. Ability to colonize meat surfaces may be a significant competitive advantage for meat spoilage bacteria such as Pseudomonas fragi and Pseudomonas fluorescens.     

假单胞菌降解含油脂废水的研究

从含油脂污水、污泥中通过驯化筛选得到降解油脂能力强的两株菌，经全自动微生物鉴定仪鉴定两株菌都为假单胞菌：W-1为洋葱伯克霍尔德氏菌(Burkholderia cepacia)，W-2为铜绿假单胞菌(Pseudomonas aeraginosa)。其中，W-2菌株最适降解条件为pH7．0、温度30℃。实验测得所筛选菌株对油脂化工生产废水有较好的降解能力。     

肉鸡中铜绿假单胞菌的研究

目的调查屠宰前肉鸡铜绿假单胞菌的携带情况,为铜绿假单胞菌流行病学的调查和相关疾病的预防控制提供依据。方法采集49份屠宰前肉鸡的肛拭子,并分离可疑菌株,对分离到的菌株进行氧化酶实验、绿脓菌素试验和VITEK生化鉴定实验。结果从49份屠宰前肉鸡中分离出8株可疑菌株,阳性检出率为16.3%。通过形态学观察、生化鉴定,8株可疑菌株均被鉴定为铜绿假单胞菌。8株可疑菌株的生化反应结果符合铜绿假单胞菌的生化反应特点。结论健康肉鸡可携带铜绿假单胞菌。铜绿假单胞菌可作为一种食源性致病菌而危害人类健康。     

Growth of Pseudomonas weihenstephanensis,Pseudomonas proteolytica and Pseudomonas sp. in raw milk: Impact of residual heat-stable enzyme activity on stability of UHT milk during shelf-life

One of the reasons for spoilage of UHT milk during shelf-life is the presence of residual proteolytic activity produced from Pseudomonas spp. during storage of raw milk. The aim of this study was to describe the product defects occurring in indirectly heated UHT milk during shelf-life, and to establish a correlation between proteolytic activity and onset of product spoilage. UHT milk was produced from raw milk incubated with different Pseudomonas strains, and examined over four months during storage at 20 °C. Inactivation kinetics of the peptidases were determined. In UHT milk, product defects occurred in the order: bitterness – particles – creaming – sediment – gelation in all the samples containing peptidases (apparent enzyme activity ≥ 0.03 pkat mL⁻¹). A linear correlation was found between proteolytic activity and onset of product defects, apart from onset of gelation.     

假单胞菌胞外弹性蛋白酶的纯化研究

假单胞菌的发酵液经过硫酸铵盐析、透析、DEA E-Sephadex A25阴离子交换层析、Sephadex G75凝胶过滤层析等纯化步骤,获得了较纯的酶蛋白。SDS-PAGE凝胶电泳:分离胶12%、压缩胶4%,15m A、30m A恒流电泳后,采用考马斯亮蓝染色和银染色,并用H PLC检测,将蛋白质转移到PV DF膜上,N-端测定10个氨基酸序列。结果表明:SDS-PAGE电泳得到单一条带,H PLC检测活性峰为单峰。该酶在SD S-PAG E上测得的分子质量为32000Da,N-端氨基酸测序结果为APPSNLM QLP。     

水样中绿脓杆菌产色素的初步研究

绿脓杆菌能产生包括绿脓素在内的多种色素[1],色素产生受多种因素的影响.培养基的不同,绿脓杆菌色素生成也不同,现对2010年水样中所监测到的绿脓杆菌在不同培养基上所产生的色素进行分析,发现镁离子与甘油在一定浓度下对其色素生成促进效果最好.通过对培养基中影响绿脓杆菌色素产生的影响因素了解,有利于水中绿脓杆菌色素差异菌株的...     

恶臭假单胞菌发酵条件的研究

从未发病的K326烟株根际土壤中筛选出对TMV具有高度拮抗活性菌株A3,发酵液的抑制效果可达95%以上,为此,从碳源、氮源、pH、温度、通气量及发酵时间等方面对该菌株的摇瓶发酵条件进行研究。结果表明,A3菌株发酵适宜温度为28 ℃,在该温度下发酵60～70 h达到菌体最大数量,且抑菌效价最高;以葡萄糖为适宜的碳源可以更好的促进菌量的生长和抗病毒物质的分泌,有机氮中酵母膏或蛋白胨对菌株的生长和抗病毒活性成分生成均能达到理想的效果,鱼粉则不能被A3菌株很好的利用;pH 7是菌株最适宜的发酵范围,偏酸不利于菌株的生长;适当加大通气量能更好地促进A3菌株的繁殖及抗病毒物质的分泌。     

PF7-5对烟草野火病的抑制及田间防治效果

为验证荧光假单胞杆菌PF7-5(CGMCC No.2069)对烟草野火病菌(Pseudomonas syringae pv.tabaci)的生防效果,设置了PF7-5对烟草野火病菌的室内抑菌及田间防治试验.结果表明,稀释5倍的PF7-5代谢产物室内对烟草野火病菌的抑制效果达96%,PF7-5活菌田间抑菌效果达91%.证实PF7-5对烟草野火病具有显著的拮抗作用和防治效果.     

Bioconversion of (+)-Limonene by Pseudomonas gladioli

Pseudomonas gladioli was isolated by an enrichment culture technique using limonene as the sole source of carbon. Fermentations were conducted for 4–10 days in shake flasks at 25°C using a pH 6.5 mineral salts medium and 1.0% (+)-limonene. Major conversion products were identified as (+)-α-terpineol and (+)-perillic acid. Quantitative analysis of α-terpineol and perillic acid during the fermentation revealed that α-terpineol was resistant to further degradation by the bacterium, while perillic acid was readily degraded.     

铜绿假单胞菌在牛乳中生长的预测

以食源致病性铜绿假单胞菌ATCC27853为试材,研究其在牛乳中的生长模型参数与温度之间的关系,为其在牛乳中的安全控制提供理论依据。将ATCC27853接种于新鲜灭菌的牛乳中,分别置于6、10、16、22、28、36、42、45、48、50 ℃共10 个温度下生长,采用Matlab软件建立了在不同温度下ATCC27853的一级Gompertz模型;基于Gompertz模型拟合的参数,结合修正Ratkowsky模型与Hyperbola模型,分别建立了ATCC27853的最大比生长速率（μmax）与温度、延滞时间（λ）与温度之间的二级模型;采用决定系数、均方根误差、准确因子和偏差因子对ATCC27853的一级和二级模型进行评价。对一级Gompertz模型和二级修正Ratkowsky模型、Hyperbola模型进行验证,结果表明：一级Gompertz模型显著,能较好地预测不同温度下ATCC27853在牛乳中的生长;二级修正Ratkowsky模型和Hyperbola模型均显著,且拟合度较好;在6、10、48 ℃时,初始生理状态参数（h0）明显高于16～45 ℃时。ATCC27853的生长温度对μmax、λ和h0的影响可用于其在牛乳的加工、运输、贮藏和销售等过程中的安全预测,为ATCC27853在牛乳中的安全控制提供理论依据。     

临床分离铜绿假单胞菌的耐药性研究

目的 了解医院分离的铜绿假单胞菌感染分布及目前临床常用14种抗菌药物的耐药情况,指导临床合理选用抗菌药物.方法 用K-B法分析2001～2004年间95株铜绿假单胞菌与14种常用抗生素的药敏性.结果 实验菌株对14种抗菌药物都显示了较强的耐药率,其中对复方磺胺甲噁唑、四环素、氯霉素、环丙沙星、庆大霉素、左氧氟沙星、妥布霉素的耐药率均超过70％,且96.8％的菌株耐受3种以上抗菌药物.结论 铜绿假单胞菌的耐药性突出.感染铜绿假单胞菌应在药敏实验指导下用药,治疗首选头孢他啶、阿米卡星或亚胺培南与氨基糖苷类联合治疗.     

硝基还原假单胞菌谷氨酰胺酶的分离纯化及酶学性质

采用离子交换层析和凝胶过滤层析等方法,分离纯化硝基还原假单胞菌(Pseudomonas nitroreducens)SK16.004所产的谷氨酰胺酶,并进一步研究该酶的酶学性质及反应动力学参数。结果表明,该酶的最适反应温度为55℃,最适pH为9.0,温度稳定范围为37～60℃,pH稳定范围为5.0～11.0;Cu2+对促进酶活提高作用最大,而Fe3+会抑制该酶的转移活力。谷氨酰胺酶对底物谷氨酰胺的亲和力最强,其Km值为0.72 mmol/L,Vmax为0.55μmol/(min.mL)。     

Autolysis of the proteinase from Pseudomonas fluorescens.

The gene encoding the proteinase from Pseudomonas fluorescens was cloned and sequenced in an effort to identify the cleavage sites involved in its autolysis at 50 degrees C. A single open reading frame consisting of 1449 nucleotides, encoding a protein of 482 amino acids, was found. Analysis of the N-terminal amino acid sequence of the purified proteinase indicated the presence of a prosequence consisting of 13 amino acid residues. The molecular weight of the mature protein was calculated as 48,900 based on the deduced amino acid sequence, which was consistent with that of the purified proteinase as determined by sodium dodecylsulfate-PAGE. Greater than 90% loss of proteolytic activity was observed upon heating at 50 degrees C for 2 min compared with the unheated enzyme. Incubation of the proteinase at 50 degrees C led to disappearance of the intact enzyme, as shown by sodium dodecyl sulfate-PAGE, whereas it was stable in the presence of the protease inhibitor o-phenanthroline. Autolytic fragments were fractionated by reverse-phase HPLC and subjected to N-terminal amino acid sequence analysis in an effort to determine the cleavage sites. The cleavage profile was not definitive; however, amino acid residues with small side chain groups, such as glycine or alanine, were frequently found adjacent to the cleavage sites.     

乳酸钠抑制铜绿假单胞菌生长的机理

为探索乳酸钠(NaL)抑制铜绿假单胞菌(Pseudomonas aeruginosa)生长的机理,从NaL影响目标菌细胞膜(壁)结构完整性和胞内ATP的合成两方面进行了探讨。研究结果表明,0.02 g/mL NaL显著破坏了细胞膜结构的完整性,对照组破坏程度较小,两者差异显著(P<0.05);另一方面,0.02 g/mL NaL抑制了胞内ATP合成,而对照组中ATP含量明显高于NaL试验组(P<0.05)。试验结果为合理、高效利用乳酸钠为新型肉类防腐剂提供了理论依据。     

Growth Inhibition of a Pseudomonas by Carbon Dioxide

SUMMARY— Growth rate studies were conducted with Pseudomonas aeruginosa to measure the inhibitory effect of CO₂ when such variables as temperature, O₂, tension, pH, and ionic strength of the glucose-salts medium were controlled. Depletion of O₂ did not limit growth until more than 75% (v/v) of the air was replaced with nitrogen. Generation time increased with ionic strength of the medium. The influence of pH in the range of 6.0 to 7.4 on the growth rate was negligible. When these variables were controlled, a linear relationship between generation time and CO₂ composition of the gas phase was observed. At 70% CO₂ (v/v), the generation time was nearly doubled. Thus, CO₂ inhibits the metabolism of the organism, and this inhibition is due to gaseous CO₂ in the air only when other environmental factors are controlled.