Inactivation of Legionella pneumophila and Pseudomonas aeruginosa: evaluation of the bactericidal ability of silver cations

In this study, silver cations dissolved as silver nitrate at various concentrations were exposed to Legionella pneumophila, Pseudomonas aeruginosa, and Escherichia coli to quantitatively estimate the bactericidal ability of silver. Observed data were analyzed using a newly developed model (Cs x T) that introduced a specific amount of chemisorbed silver onto a bacterial cell (Cs), which represented the chemisorption properties of silver on the bacterial cell body. Silver cations were rapidly chemisorbed onto bacterial cells after injection into samples, and Cs values (initial concentration of silver was 0.1 mg Ag/l) were calculated as 1.810 x 10(-6) (L. pneumophila), 1.102 x 10(-6) (P. aeruginosa), and 1.638 x 10(-6) microg Ag/cell(i) (E. coli) after incubation for 8 h. During that time, the three tested bacteria were completely inactivated under the detection limit (>7.2 log reduction). Based on the calculated Cs values, bacterial tolerance against silver was estimated by using the equation (Cs x T) multiplying the Cs values with exposure time (T). The Cs x T values well represented the bactericidal abilities of silver against the tested bacteria. The demanded Cs x T values to accomplish a 1 log inactivation (90% reduction) of L. pneumophila, P. aeruginosa, and E. coli (the initial numbers of bacteria were 1.5 x 10(7) CFU/ml, approximately) were estimated as 2.44 x 10(-6), 0.63 x 10(-6), and 0.46 x 10(-6) microgh/cell(i) of silver. The values were significantly reduced to 1.54 x 10(-6), 0.31 x 10(-6), and 0.25 x 10(-6) microgh/cell(i), respectively, with simultaneous injection of silver and copper. This study shows the successful quantitative estimation of the bactericidal ability of silver by applying the newly developed model (Cs x T). Among the tested bacteria, L. pneumophila showed the strongest tolerance to exposure of the same concentration of silver.     

Effects of nutrients on biofilm formation and detachment of a Pseudomonas putida strain isolated from a paper machine

The aim of this study was to determine the effect of varying nutrient conditions on biofilm formation of a Pseudomonas putida strain isolated from a paper machine under controlled conditions. Biofilm accumulation, was investigated using a laminar flow cell reactor in a defined mineral medium. Our results indicate that increasing nutrient concentration (from 0.1 to 0.5gl(-1) glucose, C/N=40, C/P=100) or phosphate concentration (from C/P=200 to C/P=100) increased the rate and extent of biofilm accumulation, however, higher nutrient (1gl(-1) glucose, C/N=40, C/P=100) or phosphate (C/P=50) concentration reduced biofilm accumulation rate because of a higher detachment. The rate and extent of biofilm accumulation increased with nitrogen concentration (from C/N=90 to C/N=20). Detachment is a key parameter that influences biofilm accumulation since the early stage (2h) of colonisation and strongly depends on nutrient conditions. In practice, controlling nutrient levels may be interesting to reduce biofilm formation in the paper industry.     

胞外弹性蛋白酶的理化特性及其影响因素

分离得到的假单胞菌(Pseudomonas sp) 菌株具有较强的分泌胞外弹性蛋白酶的能力。经微生物发酵方法生产的弹性蛋白酶,经过盐析、透析、DEAE SephadexA2 5离子交换层析、SephadexG75凝胶过滤层析等纯化步骤,从其发酵液中得到了均一的酶制品。研究结果表明,酶的最适作用温度为5 0℃;在硼砂-硼酸缓冲液中最适作用pH为8 0左右;酶在碱性环境下( pH7 0～12 0 )稳定性较好;在37℃以下,酶的稳定性较高。超过6 0℃,酶在短时间内即失活     

冷却肉中假单胞菌生长动力学模型的建立

为能够准确预测冷却肉的货架期,以从冷却肉中分离得到特定腐败菌——铜绿假单胞菌C272为研究对象,建立其生长动力学模型。分别在0、4、8、12、25℃液态培养条件下,测定不同培养期内的菌数。结果表明:利用Matlab工具拟合不同温度下的生长情况,Gompertz模型能较好地描述铜绿假单胞菌C272在不同温度下的生长动态,平方根模型能很好地呈现温度对最大比生长速率的影响关系,二次多项式能很好地呈现温度对迟滞期与最大细胞密度的影响关系,再把冷却肉置于4℃和7℃温度下贮藏,分别测定不同贮藏时间的菌数,对模型进行验证,由此所建立的次级模型可以有效预测冷却肉在4～25℃条件下铜绿假单胞菌C272的生长情况。     

Blocking of Pseudomonas aeruginosa and Chromobacterium violaceum lectins by diverse mammalian milks

Pseudomonas aeruginosa and Chromobacterium violaceum morbid and mortal infections are initiated by bacterial adherence to host-cell receptors via their adhesins, including lectins (which also contribute to bacterial biofilm formation). Pseudomonas aeruginosa produces a galactophilic lectin, PA-IL (LecA), and a fucophilic (Lewis-specific) lectin, PA-IIL (LecB), and C. violaceum produces a fucophilic (H-specific) lectin, CV-IIL. The antibiotic resistance of these bacteria prompted the search for glycosylated receptor-mimicking compounds that would function as glycodecoys for blocking lectin attachment to human cell receptors. Lectins PA-IL and PA-IIL have been shown to be useful for such glycodecoy probing, clearly differentiating between human and cow milks. This article describes their usage, together with CV-IIL and the plant lectin concanavalin A, for comparing the anti-lectin-dependent adhesion potential of diverse mammalian milks. The results show that the diverse milks differ in blocking (hemagglutination inhibition) and differential binding (Western blots) of these lectins. Human milk most strongly inhibited the 3 bacterial lectins (with PA-IIL superiority), followed by alpaca, giraffe, and monkey milks, whereas cow milk was a weak inhibitor. Lectin PA-IL was inhibited strongly by human, followed by alpaca, mare, giraffe, buffalo, and monkey milks, weakly by camel milk, and not at all by rabbit milk. Lectins PA-IIL and CV-IIL were also most sensitive to human milk, followed by alpaca, monkey, giraffe, rabbit, and camel milks but negligibly sensitive to buffalo and mare milks. Plant lectin concanavalinA, which was used as the reference, differed from them in that it was much less sensitive to human milk and was equally as sensitive to cow milk. These results have provided important information on the anti-lectin-dependent adhesion potential of the diverse milks examined. They showed that human followed by alpaca, giraffe, and Rhesus monkey milks efficiently blocked the binding of both the galactophilic and fucophilic (>mannophilic) pathogen lectins. The results also proved the advantage of isolated pathogenic bacterial lectins as superb probes for unveiling bacterial adhesion-blocking glycodecoys. The chosen milks or their polymeric glycans might be implicated in blocking lectin-dependent adhesion of antibiotic-resistant pathogens leading to skin, eye, ear, and gastrointestinal infections.     

纳米硒化荧光假单胞菌KBD-1菌株对烟草病毒病的抑制作用

为挖掘具有纳米硒化能力的生防菌株,开发烟草病毒病的绿色防治材料,从烟草病毒病重病田块健株根际土壤中筛选获得到一株荧光假单胞菌Pseudomonas fluorescens KBD-1,对其进行了纳米硒化,采用Real-time PCR和Western blot测定了两者对烟草常见病毒基因表达的影响,并采用接种法测定了其对烟株相应病毒病的防治作用。结果表明,纳米硒化后的KBD-1菌体外部存在高密度电子颗粒,在X射线11.22 keV处出现硒的特征吸收峰。纳米硒化后的P.fluorescens KBD-1菌液浓度在5×10⁵ cfu/mL（单质硒浓度0.25 mg/L）时,对烟草花叶病毒（TMV）、马铃薯Y病毒（PVY）、黄瓜花叶病毒（CMV）、番茄斑萎病毒（TSWV）4种病毒病的防治效果均在88.0%以上,对CMV防治效果最高达91.4%,该浓度处理对烟株促生效果显著。荧光假单胞菌KBD-1可成功将亚硒酸钠还原生成纳米硒,并能增强原始菌株的抗烟草病毒活性和促生效果。     

Different specificity of two types of Pseudomonas lipases for C20 fatty acids with a Delta5 unsaturated double bond and their application for selective concentration of fatty acids

Two kinds of lipases, AK-lipase and HU-lipase, produced by two different Pseudomonas fluorescens strains, AK102 and HU380, respectively, were evaluated as to fatty acid hydrolysis specificity using six types of oil containing higher amounts of C20 fatty acids such as arachidonic acid (5,8,11,14-eicosatetraenoic acid, AA, or 20:4omega6), dihomo-gamma-linolenic acid (8,11,14-eicosatrienoic acid, DGLA, or 20:3omega6), 5,8,11,14,17-eicosapentaenoic acid (EPA or 20:5omega3), mead acid (5,8,11-eicosatrienoic acid, MA, or 20:3omega9), 8,11-eicosadienoic acid (20:2omega9) and 8,11,14,17-eicosatetraenoic acid (20:4omega3). Although HU-lipase did not show any specificity for C20 fatty acids with respect to the presence or absence of a Delta5 unsaturated bond, it exhibited comparatively low reactivity for 4,7,10,13,16,19-docosahexaenoic acid (DHA or 22:6omega3). In contrast, AK-lipase was less reactive for C20 fatty acids with a Delta5 unsaturated bond. However, the specificity of hydrolysis of AK-lipase gradually decreased as the reaction proceeded. Utilizing this fatty acid specificity, we concentrated either EPA or DHA from fish oils containing both EPA and DHA by means of lipase-catalyzed hydrolysis and urea adduction. Hydrolysis and urea adduction of refined cod oil including 12.2% EPA and 6.9% DHA with HU-lipase provided free fatty acids with 43.1% EPA and 7% DHA, respectively. The resulting yield of concentrated total fatty acids comprised 2.6% of the fatty acids from the cod oil. Thus, EPA was particularly concentrated in the fatty acids derived from refined cod oil on partial hydrolysis with HU-lipase followed by urea adduction. On the other hand, hydrolysis of cuttlefish oil with AK-lipase followed by urea adduction increase slightly the EPA composition from 14.2% to 16.8%, and markedly enhanced the composition of DHA from 16.3% to 44.6% in the hydrolyzed fatty acids. The yield of purified total fatty acids by urea concentrate was 9.4% of the fatty acids from the cuttlefish oil. Thus, DHA was particularly concentrated in the fatty acids derived from on partial hydrolysis with AK-lipase followed by urea adduction. We concluded that EPA and DHA concentrates can be easily and inexpensively obtained using HU-lipase and AK-lipase, respectively. Furthermore, it might be possible to separate and concentrate C20 polyunsaturated fatty acids (PUFAs) with or without a Delta5 double bond from PUFAs rich oils including both fatty acids.     

响应面法优化假单胞菌TS1138的产酶条件(英文)

以假单胞菌(Pseudomonas sp.)TS1138为供试菌株,运用响应面法对酶法合成L-半胱氨酸所用酶的生产条件进行优化。首先利用Plackett-Burman设计从影响TS1138菌株产酶的众多因素中筛选出影响较大的四个因素:DL-ATC 、玉米浆、转速和装液量。在此基础上再利用二次响应面分析法进行优化,得出了最佳的实验条件。最佳产酶培养基配方为(g/L):葡萄糖 30、DL-ATC·3H2O 3.0、玉米浆 3.1、尿素 3、MnSO4·H2O 1、K2HPO4·3H2O 3、FeSO4·7H2O 0.01、MgSO4·7H2O 0.5、NaCl 3;最佳产酶培养条件为:摇床转速 190r/min、500ml摇瓶装液量 42ml、接种量 10%、产酶培养基初始 pH7.5、培养温度 29℃。在优化条件下进行产酶培养,细胞酶活力达 2255U/ml,比未优化前的 2053U/ml 提高了 9.8%。     

荧光假单胞菌Pseudomonas fluorescence SK17.001转化生产乳糖酸的条件研究

利用荧光假单胞菌SK17.001为出发菌株,转化乳糖生产乳糖酸。通过研究发酵条件和培养基成分对乳糖转化率影响,表明荧光假单胞菌SK17.001的最适合转化条件为：培养温度30℃,pH6.5,250mL摇瓶中液体培养基装液量为30mL,摇床转速为200r/min,最佳氮源为1%蛋白胨和1%酵母膏,培养时间55h,乳糖浓度为3%时,转化率可达96%。     

不同品牌CN琼脂上铜绿假单胞菌色素表达的研究

目的 对铜绿假单胞菌在不同品牌CN琼脂上的色素表达及其原因进行研究。方法 比较ATCC 10145、ATCC 15442、CMCC 10104 3种铜绿假单胞菌标准菌株在5种不同品牌CN琼脂上的色素表达, 并测定CN琼脂的磷含量。结果 5种CN琼脂的磷含量在123~1560 mg/kg之间, 最高的磷含量与最低磷含量相差10余倍。只产青脓素的铜绿假单胞菌ATCC 15442在各CN琼脂上均为黄色菌落, 在紫外线下产荧光。只产绿脓菌素的铜绿假单胞菌ATCC 10145, 在含磷量低的CN琼脂上呈现为蓝色菌落, 表现为产绿脓菌素; 而随着磷含量的增加, CN琼脂上绿脓菌素的表达逐渐减弱。既产绿脓菌素又产青脓素的铜绿假单胞菌CMCC 10104在含磷量低的CN琼脂上呈现为蓝色菌落, 表现为产绿脓菌素; 而随着磷含量的增加, CN琼脂上绿脓菌素的表达逐渐减弱, 青脓素的表达逐渐增强, 菌落颜色逐渐变黄并在紫外线下产荧光。结论 铜绿假单胞菌在5种不同品牌的CN琼脂上的表达色素的情况与CN琼脂的磷含量有关, CN琼脂含磷量越低, 越有利于绿脓菌素的表达, 青脓素的表达受到抑制; CN琼脂含磷量越高, 越有利于青脓素的表达, 绿脓菌素的表达受到抑制。