Although researchers can access information on the entire genomic DNA sequence of typical research organisms, convenient genome walking methods in the laboratory are still needed. For the analysis of microorganisms, these methods are especially useful because the available genetic information is often scarce or limited.Many genomic walking methods are based on the polymerase chain reaction (PCR), and useful methods have been developed. This report reviews the methodologies of PCR-mediated genomic walking methods and evaluates their efficiency and usefulness to help microbiologists to select the appropriate method for each target microorganism. The concept and specific features, such as advantages and disadvantages, of five major PCR-mediated genomic walking methods (random PCR, inverse PCR, panhandle PCR, cassette PCR, and rapid amplification of genomic ends) are briefly described. The improved methods and their characteristics are listed, and a report of experimental comparison of such methods is also introduced briefly. Each of these methods has both advantages and disadvantages, and there is a trade-off between the specificity of target amplification and the ease of the method. The cassette PCR seems to be a standard method, but suitable method should be selected in consideration of the characteristics of the material.
Because global climate change has made agricultural supply unstable, plant factories are expected to be a safe and stable means of food production. As the light source of a plant factory or controlled greenhouse, the light emitting diode (LED) is expected to solve cost problems and promote plant growth efficiently. In this study, we examined the light condition created by using monochromatic red and blue LEDs, to provide both simultaneous and alternating irradiation to leaf lettuce. The result was that simultaneous red and blue irradiation promoted plant growth more effectively than monochromatic and fluorescent light irradiation. Moreover, alternating red and blue light accelerated plant growth significantly even when the total light intensity per day was the same as with simultaneous irradiation. The fresh weight in altering irradiation was almost two times higher than with fluorescent light and about 1.6 times higher than with simultaneous irradiation. The growth-promoting effect of alternating irradiation of red and blue light was observed in different cultivars. From the results of experiments, we offer a novel plant growth method named "Shigyo Method", the core concept of which is the alternating irradiation of red and blue light.
Paramecium bursaria, a freshwater protozoan, typically harbors hundreds of symbiotic algae (Chlorella sp.) in its cytoplasm. The relationship between host paramecia and symbiotic algae is stable and mutually beneficial in natural environments. We recently collected an aposymbiotic strain of P. bursaria. Infection experiments revealed that the natural aposymbiotic strain (Ysa2) showed unstable symbiosis with Chlorella sp. The algae aggregated at the posterior region of the host, resulting in aposymbiotic cell production after cell division. Cross-breeding analyses were performed to determine the heritability of the aposymbiotic condition. In crosses of Ysa2 with symbiotic strains of P. bursaria, F1 progeny were able to form stable symbioses with Chlorella sp. However, unstable symbiosis, resembling Ysa2 infection, occurred in some F2 progeny of sibling crosses between symbiotic F1 clones. Infection experiments using aposymbiotic F2 cells showed that these F2 subclones have limited ability to reestablish the symbiosis. These results indicate that the maintenance of stable symbiosis is genetically controlled and heritable, and that Ysa2 is a mutant lacking the mechanisms to establish stable symbiosis with Chlorella sp.
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