nuoB对莓实假单胞菌生理特性及在冷鲜鸡肉中致腐能力的影响

【目的】研究nuoB对莓实假单胞菌菌体特性及其对冷鲜鸡肉致腐能力的影响,为揭示nuoB介导的冷鲜鸡肉腐败机制,开发新型保鲜技术提供理论依据。【方法】通过构建nuoB插入失活突变株,对比野生株和突变株在体外培养条件下的生长曲线、聚集性、泳动性和生物被膜形成能力;以及原位培养条件对冷鲜鸡肉的致腐特征,包括菌落总数、挥发性盐基氮(TVBN)含量、pH和感官评分,探讨nuoB对莓实假单胞菌生理特性和致腐作用的影响。【结果】体外培养条件下,nuoB并未影响莓实假单胞菌的生长能力、聚集性和swarming泳动性,但突变株的swimming泳动性和生物被膜形成能力在培养过程中显著下降。原位条件下,对冷鲜鸡肉致腐能力的评估发现两组样品菌落总数差异不显著,均达到了10 lg CFU·g^(-1);突变株组在冷鲜鸡肉储藏期间TVBN均显著低于野生株组,在第4天时才超过国家标准限量15 mg/100 g,培养末期的最大值约为野生株组的1/2;培养前2 d所有样品的pH均处于正常范围内,突变株组的pH从培养第5天开始显著低于野生株组;感官评价结果显示培养第4天时的两组样品均出现了黏液和异味,被判定为腐败,但突变株组样品稍弱于野生株组。【结论】nuoB的破坏没有影响莓实假单胞菌的生长能力,但抑制了菌株的泳动性、生物被膜形成和对冷鲜鸡肉的致腐能力。

微生物菌液物质油水界面扩张黏弹性研究

采用小幅低频振荡法,研究了常温菌与高温菌菌液物质在油-水界面上的扩张黏弹特性及动态界面张力,阐述了菌液物质黏弹模量随扩张频率及温度的变化规律,获得了菌液物质油水界面吸附动态微观信息,并将扩张流变性质与动态界面张力相关联,定量考察了菌体本身对油水界面性质的影响.研究结果表明:菌液物质黏弹模量随扩张频率的增加而增加,随温度的升高而降低;菌体本身具有界面活性,能够降低界面张力和黏弹模量,改变油水界面性质,提高原油流动性能.但其活性受温度的影响,存在最佳活性温度.现场应用时应注意油藏温度与菌液最佳活性温度一致.

Isolation and Biological Characteristics of Bacteriophage of an Antibiotic-resistant Escherchia coli Strain

In this study, bacteriophage of an antibiotic-resistant Escherchia coil strain isolated from feces of chicken was isolated. Its host range was determined by the method of spotting sample on monolayer agar, and its lysis titer, optimal multiplicity of infection （MOI）, temperature tolerance and pH tolerance were determined by the double-layer agar plate method. The results showed that the bacteriophage had a broad host range. The biological assay demonstrated that two strains of E. coil were fully lysed and one strain of E. coil was weakly lysed by the bacteriophage. The lysis titer and MOI of the bacteriophage were 1.20×10^8 PFU/ml and 1, respec- tively. Under the optimum temperature of 40℃, the Jysis titer of the bacteriophage reached 8.90×10^9 PFU/ml; however, the bacteriophage lost its infectivity at the tem- perature of 80℃. In the pH range of 5-11, the lysis titer of the bacteriophage ranged from10^6 to 10^9 PFU/mI. Under the condition of pH 4 and 12, the bacterio- phage was invalid.

The Ploidy of Yeast and Its Identification Method

[Objective] The aim was to indentify haploid and diploid yeast.[Method] The characteristics of haploid and diploid yeast and their relation were analyzed firstly,and then haploid and diploid yeast were indentified through the methylene blue staining,safranine staining of ascospore and special low temperature treatment test.[Result] After methylene blue staining,the differences of haploid and diploid yeast in activity and size could be observed clearly;the ascospores of diploid strains after sporulating became red after safranine staining,and diploid thalluses were blue,while there were only blue thalluses for haploid strains;after special low temperature treatment,the colony of diploid was obviously larger than that of haploid on the plate.[Conclusion] Haploid and diploid yeast had great differences in morphology,heredity and physiology and could be identified well by means of aided test.

Isolation and rapid genetic characterization of a novel T4-like bacteriophage

Ubiquitous on earth,bacteriophages are the most abundant entities in every ecosystem,but human knowledge about them is still limited compared with that about other forms of organisms.To enrich human knowledge and promote the utilization of bacteriophages,it is necessary to isolate and characterize as many as possible different bacteriophages.Here we describe the isolation of a T4-like bacteriophage IME08 and a rapid method for its genetic characterization.With this method we easily cloned a few random fragments of the bacteriophage genome.Sequence analysis of these random clones showed that bacteriophage IME08 shared the highest sequence similarity with T4-like Enterobacteria phage T4（94%identity）,JS98（95% identity）,JS10（95%identity） and RB14（94%identity） respectively,which suggested that IME08 belonged to T4-like bacteriophage genus.

Affinity peptide developed by phage display selection for targeting gastric cancer

AIM:To develop an affinity peptide that binds to gastric cancer used for the detection of early gastric cancer.METHODS:A peptide screen was performed by biopanning the PhD-12 phage display library,clearing non-specific binders against tumor-adjacent normal appearing gastric mucosa and obtaining selective binding against freshly harvested gastric cancer tissues.Tumortargeted binding of selected peptides was confirmed by bound phage counts,enzyme-linked immunosorbent assay,competitive inhibition,fluorescence microscopy and semi-quantitative analysis on immunohistochemistry using different types of cancer tissues.RESULTS:Approximately 92.8% of the non-specific phage clones were subtracted from the original phage library after two rounds of biopanning against normal-appearing gastric mucosa.After the third round of positive screening,the peptide sequence AADNAKTKSFPV(AAD) appeared in 25%(12/48) of the analyzed phages.For the control peptide,these values were 6.8 ± 2.3,5.1 ± 1.7,3.5 ± 2.1,4.6 ± 1.9 and 1.1 ± 0.5,respectively.The values for AAD peptide were statistically signif icant(P < 0.01) for gastric cancer as compared with other histological classif ications and control peptide.CONCLUSION:A novel peptide is discovered to have a specific binding activity to gastric cancer,and can be used to distinguish neoplastic from normal gastric mucosa,demonstrating the potential for early cancer detection on endoscopy.

Detection and evaluation of antibodies against neutrophil-activating protein of Helicobacter pylori in patients with gastric cancer

AIM： To detect and evaluate the antibodies against Helicobacter pylori （H pylori） neutrophil-activating protein （HP-NAP） in patients with gastric cancer and other gastroduodenal diseases.METHODS： Recombinant HP-NAP was prepared from a prokaryotic expression system in Escherichia coll. Serum positivity and level of HP-NAP-specific antibodies in sera from 43 patients with gastric cancer, 28 with chronic gastritis, 28 with peptic ulcer, and 89 healthy controls were measured by rHP-NAP-based ELISA. rHP-NAP-stimulated production of interleukin-8 （IL-8） and growth-related oncogene （GROα） cytokines in the culture supernatant of SGC7901 gastric epithelial cells was also detected.RESULTS： The serum positivity and mean absorbancevalue of HP-NAP-specific antibodies in the gastriccancer group （97.7% and 1.01 ± 0.24） were significantly higher than those in the chronic gastritisgroup （85.7% and 0.89 ± 0.14, P 〈 0.005） and healthy control group （27.7% and 0.65 ± 0.18, P 〈 0.001）. The sensitivity and specificity of ELISA for the detection of HP-NAP-specific antibodies were 95.5% and 91.5%, respectively. HP-NAP could slightly upregulate IL-8 production in gastric epithelial cell lines but had no effect on GROα production.CONCLUSION： Infection with virulent H py/ori strains secreting HP-NAP is associated with severe gastroduodenal diseases, and HP-NAP may play a role in the development of gastric carcinoma, rHP-NAP- based ELISA can be used as a new method to detect H pylori infection. The direct effect of HP-NAP on gastric epithelial cells may be limited, but HP-NAP may contribute to inflammatory response or carcinogenesis by activating neutrophils.