A Comparison of Fluorescent Pigments From Flavobacterium and Sphingobacterium Species

Abstract

An extraction procedure was developed for the isolation of fluorescent pigments from species of Flavobacterium and Sphingobacterium. This procedure was conducted at room temperature. Thereby the possibility of thermal degradation of the fluorescent pigments present in these organisms was reduced compared to previously reported extraction methods in which pigments were extracted after heating with strong base. Extracts from strains of eight species of these two genera have been evaluated using a video fluorometer (VF). This instrument rapidly provides a two-dimensional fluorescence spectrum of each extract. Data from replicate extracts of the organisms have been compared in order to evaluate the potential for identification of these microorganisms on the basis of their fluorescent pigment content. Similarities between the fluorescence spectra of two of the Flavobacterium species and Sphingobacterium mizutae support earlier studies which have shown that these organisms are related on the basis of their content of menaquinones and cellular fatty acids.     

Organotin compounds in agriculture since 1980. Part 2. Acaricidal,antifeedant, chemosterilant and insecticidal properties

The object of this review paper is to provide a guide to agrochemical research involving organotin compounds which has been performed since 1980. The information is presented in a tabular form and is divided into four main sections as indicated by the title. Each section is then subdivided to cover the various commercial organotin compounds. A final subsection lists investigations involving novel compounds. An additional section covers the effects of organotin agrochemicals on non-target organisms. A table of the contents has been provided to enable ease of reference. Acaricidal, antifeedant, chemosterilant and insecticidal properties are covered here. Fungicidal, bactericidal and herbicidal aspects are covered in Part 1.     

Biomineralization of unicellular organisms: an unusual membrane biochemistry for the production of inorganic nano- and microstructures

With evolution, Nature has ingeniously succeeded in giving rise to an impressive variety of inorganic structures. Every organism that synthesizes biogenic minerals does so in a form that is unique to that species. This biomineralization is apparently biologically controlled. It is thus expected that both the synthesis and the form of every specific biogenic mineral is genetically determined and controlled. An investigation of the mechanism of biomineralization has only become possible with the development of modern methods in molecular biology. Unicellular organisms such as magnetic bacteria, calcareous algae, and diatoms, all of which are amongst the simplest forms of life, are particularly suited to be investigated by these methods. Crystals and composites of proteins and amorphous inorganic polymers are formed as complex structures within these organisms; these structures are not known in conventional inorganic chemistry.     

Development of classification models for predicting chronic toxicity of chemicals to Daphnia magna and Pseudokirchneriella subcapitata

Both the acute toxicity and chronic toxicity data on aquatic organisms are indispensable parameters in the ecological risk assessment priority chemical screening process (e.g. persistent, bioaccumulative and toxic chemicals). However, most of the present modelling actions are focused on developing predictive models for the acute toxicity of chemicals to aquatic organisms. As regards chronic aquatic toxicity, considerable work is needed. The major objective of the present study was to construct in silico models for predicting chronic toxicity data for Daphnia magna and Pseudokirchneriella subcapitata. In the modelling, a set of chronic toxicity data was collected for D. magna (21 days no observed effect concentration (NOEC)) and P. subcapitata (72 h NOEC), respectively. Then, binary classification models were developed for D. magna and P. subcapitata by employing the k-nearest neighbour method (k-NN). The model assessment results indicated that the obtained optimum models had high accuracy, sensitivity and specificity. The model application domain was characterized by the Euclidean distance-based method. In the future, the data gap for other chemicals within the application domain on their chronic toxicity for D. magna and P. subcapitata could be filled using the models developed here.     

Protein-Based Biosensors for Diabetic Patients

In this article we show the recent progress in the field of glucose sensing based on the utilization of enzymes and proteins as probes for stable and non-consuming fluorescence biosensors. We developed a new methodology for glucose sensing using inactive forms of enzymes such as the glucose oxidase from Aspergillus niger, the glucose dehydrogenase from the thermophilic microorganism Thermoplasma acidophilum, and the glucokinase from the thermophilic eubacterium Bacillus stearothermophilus. Glucose oxidase was rendered inactive by removal of the FAD cofactor. The resulting apo-glucose oxidase still binds glucose as observed from a decrease in its intrinsic tryptophan fluorescence. 8-Anilino-1-naphthalene sulfonic acid was found to bind spontaneously to apo-glucose oxidase as seen from an enhancement of the ANS fluorescence. The steady state intensity of the bound ANS decreased 25% upon binding of glucose, and the mean lifetime of the bound ANS decreased about 40%. These spectral changes occurred with a midpoint from 10 to 20 mM glucose, which is comparable to the KD of holo-glucose oxidase. The ANS-labeled apo-glucose dehydrogenase from Thermoplasma acidophilum also displayed an approximate 25% decrease in emission intensity upon binding glucose. This decrease can be also used to measure the glucose concentration. The thermophilic apo-glucose dehydrogenase was also stable in the presence of organic solvents, allowing determination of glucose in the presence of acetone. The third enzyme used for glucose sensing was the glucokinase from Bacillus stearothermophilus. A fluorescence competitive assay for the determination of glucose was developed based on the utilization of this thermostable enzyme. Taken together, our results show that enzymes which use glucose as their substrate can be used as reversible and non-consuming glucose biosensors in the absence of required co-factors. Moreover, the possibility of using inactive apo-enzymes for a reversible sensor greatly expands the range of proteins which can be used as sensors, not only for glucose, but for a wide variety of biochemically relevant analytes.     

Arsenic metabolism in a freshwater food chain: Blue–green alga (Nostoc sp.)→ shrimp (Neocaridina denticulata)→ carp (Cyprinus carpio)

Bioaccumulation and biomethylation of inorganic arsenic were investigated in a three-step fresh-water food chain consisting of an autotroph (blue- green alga: Nostoc sp.), a herbivore (shrimp: Neocaridina denticulata) and a carnivore (carp: Cyprinus carpio). The autotroph, herbivore and carnivore survived in arsenic-containing water below 1000, 2 and 60 mg As(V) dm^?3, respectively. Bioaccumulation of arsenate by Nostoc sp. was decreased with an increase in the nitrogen concentration of the medium. Arsenic(V) was accumulated from the water phase and part-methylated by the carp, as well as by the algae and shrimp. Arsenic was mostly accumulated in the gut of the carp. The predominant arsenical in the guts was the monomethylarsenic species. Arsenic accumulation via food in the above three-step food chain decreased by one order of magnitude and the relative concentration of methylated arsenic to the total arsenic accumulated increased successively with an elevation in the trophic level. When arsenicals were transferred via the food chain, no monomethylarsenic, or only a trace amount, was detected in the three organisms. Dimethylarsenic in the alga, both dimethyl- and trimethyl-arsenic in shrimp, and trimethyl-arsenic in carp, were the predominant methylated arsenic species, respectively.     

海洋生物中的体化合物的研究进展

甾体化合物是一类具有显著生理活性且广泛存在于自然界中的天然化合物。本文对近年来从海洋生物中分离得到的甾体化合物,根据其结构特征对它们进行了分类总结,并对其生物活性进行了阐述,以期对甾体药物的研究开发提供有用的参考。