A Simple Test for Differentiating Streptococcus bovis from other Streptococci

S ummary . Streptococcus bovis grew in acid media, which are normally inhibitory for this organism, when incubated in an atmosphere containing 5% (v/v) CO₂ or if the CO₂ produced by the organism itself was prevented from escaping from the media. Since no other streptococcus grew in acid media under these conditions, this finding enables Strep. bovis to be differentiated from other streptococci by a simple test.     

一种利用计算机程序计算目的蛋白表达量及表达水平的方法

介绍一种利用Windows操作系统工具及扫描仪,测量和计算发酵工艺研究及摇瓶实验中目的蛋白的表达量的方法。该方法可以扩展到精确计算在琼脂、纤维膜等材料上的溶菌圈的大小、抑菌圈的大小,免疫扩散及其绝对量的确定等。     

Simple phagemid-based system for generating allele replacements in Escherichia coli.

We describe a phagemid-based system for rapidly generating chromosomal allele replacements in two steps. The system utilizes simple vector-determined selection procedures for each step and requires only that the target strain be male and sup+ (nonsuppressing for amber mutations).     

Multilocus Simple Sequence Repeat Markers for Differentiating Strains and Evaluating Genetic Diversity of Xylella fastidiosa

A genome-wide search was performed to identify simple sequence repeat (SSR) loci among the available sequence databases from four strains of Xylella fastidiosa (strains causing Pierce's disease, citrus variegated chlorosis, almond leaf scorch, and oleander leaf scorch). Thirty-four SSR loci were selected for SSR primer design and were validated in PCR experiments. These multilocus SSR primers, distributed across the X. fastidiosa genome, clearly differentiated and clustered X. fastidiosa strains collected from grape, almond, citrus, and oleander. They are well suited for differentiating strains and studying X. fastidiosa epidemiology and population genetics.     

A Simple Method for Imaging Arabidopsis Leaves Using Perfluorodecalin as an Infiltrative Imaging Medium

The problem of acquiring high-resolution images deep into biological samples is widely acknowledged¹. In air-filled tissue such as the spongy mesophyll of plant leaves or vertebrate lungs further difficulties arise from multiple transitions in refractive index between cellular components, between cells and airspaces and between the biological tissue and the rest of the optical system. Moreover, refractive index mismatches lead to attenuation of fluorophore excitation and signal emission in fluorescence microscopy. We describe here the application of the perfluorocarbon, perfluorodecalin (PFD), as an infiltrative imaging medium which optically improves laser scanning confocal microscopy (LSCM) sample imaging at depth, without resorting to damaging increases in laser power and has minimal physiological impact². We describe the protocol for use of PFD with Arabidopsis thaliana leaf tissue, which is optically complex as a result of its structure (Figure 1). PFD has a number of attributes that make it suitable for this use³. The refractive index of PFD (1.313) is comparable with that of water (1.333) and is closer to that of cytosol (approx. 1.4) than air (1.000). In addition, PFD is readily available, non-fluorescent and is non-toxic. The low surface tension of PFD (19 dynes cm^-1) is lower than that of water (72 dynes cm^-1) and also below the limit (25 - 30 dyne cm^-1) for stomatal penetration⁴, which allows it to flood the spongy mesophyll airspaces without the application of a potentially destructive vacuum or surfactant. Finally and crucially, PFD has a great capacity for dissolving CO₂ and O₂, which allows gas exchange to be maintained in the flooded tissue, thus minimizing the physiological impact on the sample. These properties have been used in various applications which include partial liquid breathing and lung inflation^5,6, surgery⁷, artificial blood⁸, oxygenation of growth media⁹, and studies of ice crystal formation in plants¹⁰. Currently, it is common to mount tissue in water or aqueous buffer for live confocal imaging. We consider that the use of PFD as a mounting medium represents an improvement on existing practice and allows the simple preparation of live whole leaf samples for imaging.     

A Simple and Effective Method for Construction of Escherichia coli Strains Proficient for Genome Engineering

Multiplex genome engineering is a standalone recombineering tool for large-scale programming and accelerated evolution of cells. However, this advanced genome engineering technique has been limited to use in selected bacterial strains. We developed a simple and effective strain-independent method for effective genome engineering in Escherichia coli. The method involves introducing a suicide plasmid carrying the λ Red recombination system into the mutS gene. The suicide plasmid can be excised from the chromosome via selection in the absence of antibiotics, thus allowing transient inactivation of the mismatch repair system during genome engineering. In addition, we developed another suicide plasmid that enables integration of large DNA fragments into the lacZ genomic locus. These features enable this system to be applied in the exploitation of the benefits of genome engineering in synthetic biology, as well as the metabolic engineering of different strains of E. coli.     

A Simple Procedure for Screening of Salmonellae using a Semi-Solid Enrichment and a Semi-Solid Indicator Medium

The incorporation of triphenylmethane dyes and divalent cations in a semi-solid medium in conjunction with a low pH retarded the motility of most enteric bacteria except for Salmonella, Enterobacter cloacae and Citrobacter freundii . The migration of the latter two species in the semi-solid medium, however, could be selectively inhibited by the incorporation of novobiocin to the medium and by incubation at 41 °C. Based on these observations, a semi-solid enrichment medium was developed and used successfully in a Salmonella screening procedure in which a semi-solid indicator medium was used as the first and a slide agglutination test as the second screen. Clinical laboratory evaluation of the procedure showed an increase of 92% in the frequency of positive isolations, with no false positives, as compared with a conventional multi-step isolation procedure.     

Simple Synthesis of Enantiomerically Pure Sauriols A and B

Sauriols A and B belong to a class of diarylbutane-lignans and exhibit antifeedant activity. We succeeded in the first synthesis of sauriols A and B by using a simple and efficient asymmetric dimerization of a cinnamic acid derivative as the key step.     

Simple synthesis of enantiomerically pure sauriols A and B

Sauriols A and B belong to a class of diarylbutane-lignans and exhibit antifeedant activity. We succeeded in the first synthesis of sauriols A and B by using a simple and efficient asymmetric dimerization of a cinnamic acid derivative as the key step.     

Efficacy of Electrolyzed Oxidizing Water for Inactivating Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes

The efficacy of electrolyzed oxidizing water for inactivating Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes was evaluated. A five-strain mixture of E. coli O157:H7, S. enteritidis, or L. monocytogenes of approximately 10⁸ CFU/ml was inoculated in 9 ml of electrolyzed oxidizing water (treatment) or 9 ml of sterile, deionized water (control) and incubated at 4 or 23°C for 0, 5, 10, and 15 min; at 35°C for 0, 2, 4, and 6 min; or at 45°C for 0, 1, 3, and 5 min. The surviving population of each pathogen at each sampling time was determined on tryptic soy agar. At 4 or 23°C, an exposure time of 5 min reduced the populations of all three pathogens in the treatment samples by approximately 7 log CFU/ml, with complete inactivation by 10 min of exposure. A reduction of ≥7 log CFU/ml in the levels of the three pathogens occurred in the treatment samples incubated for 1 min at 45°C or for 2 min at 35°C. The bacterial counts of all three pathogens in control samples remained the same throughout the incubation at all four temperatures. Results indicate that electrolyzed oxidizing water may be a useful disinfectant, but appropriate applications need to be validated.     

Simple Medium for the Selective Isolation of Bacteroides and Related Organisms, and Their Occurrence in Sewage

A medium composed of 0.009% sodium azide, 0.07% sodium deoxycholate, and 0.0007% ethyl violet in Brain Heart Infusion Agar (Difco) and a process of incubation in an atmosphere of 90% N(2) and 10% CO(2) for the selective isolation of certain members of the intestinal bacteroides are described. The medium appears to select predominantly members of the genus Bacteroides and a few of the genus Sphaerophorus. A survey of the occurrence of these organisms in sewage and various stages of sewage treatment indicates that they survive complete sewage treatment in low numbers and that their rate of decline parallels that of the coliforms. Large numbers were recovered from sludge digestion tanks, suggesting a possible role in the anaerobic breakdown of organic matter.