Soil Microorganisms
Online ISSN : 2189-6518
Print ISSN : 0912-2184
ISSN-L : 0912-2184
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Volume 34
Displaying 1-15 of 15 articles from this issue
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  • Microbial Taxonomy Based on 16S-like Ribosomal RNA Sequence
    Hiroshi OYAIZU
    Article type: Article
    1989 Volume 34 Pages 1-7
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_1
    JOURNAL FREE ACCESS
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    Systematics involves the determination of the hierarchical structure, which expresses the evolution of organisms. Morphological, physiological, and chemotaxonomic characterizations have been conventionally used for taxonomic studies of microorganisms. However, such methods have not revealed adequately the phylogenetic relationships among microorganisms. Although chemotaxonomy enable to uncover the phylogenetic differences among microorganisms, the depth and order of branchings cannot be determined. Molecular taxonomy comparing the nucleotide sequence or amino acid sequence has advantages over the above mentioned conventional methods. Differences in the nucleotide sequence of a gene (or amino acid sequence of a protein) are basically proportionate to the length of branching between organisms, and therefore the molecular taxonomic studies can reveal the depth and order of branchings. In the present study partial sequencing of 16S ribosomal RNA with reversetranscriptase was used for the taxonomic study of bacteria. The ribosomal RNAs are essential for living organisms, and the gene transfer of the RNA gene among organisms would never have happened. Furthermore, the sequencing of 16S rRNA is very simple and rapid. So far, the 16S rRNA partial sequence from positions 1220 through 1376 (158 bases) was compared among approximately 1000 bacteria. The method appears to be very useful for classifing and identifing bacteria, and could become a standard method for identification.
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  • Nutrient Competition in Soil Fungal Flora
    Hirosuke OGURA
    Article type: Article
    1989 Volume 34 Pages 9-17
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_9
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    It is necessary to realize the behaviour of soil-borne plant pathogen as a member in soil microflora. The main nutrient source of soil fungi are plant debris and living root, and they compete to insure them in many ways. In this study there were two ways for soil fungi to get nutrients from a nitrogen source and from a carbon source. In the former (about 2/3 of the fungi tested), the nitrogen source was a limiting factor for growth, and in the latter, the carbon source was also. These two types of fungi differed in their use of plant debris needed, though both of them could use many plant debris. The C-required group easily increased in soil with high C/N ratio debris like rice straw, on the contrary, the N-required group did easier under low C/N ratio debris such as leguminous plants. There were also some fungi of a middle type between the two groups. When a fungus contacted with these groups for nutrient competition, its behaviour was different respectively. Active competition occurred within the same nutrient group to get the same foods or to maintain a wide space for its existence among the limited nutrients. In the other group however, the fungus was forced to endure as a recessive group in the flora. In this case, the fungus was always in position as the alien. If the C/N ratio in soil was considerably different from that of the root exudate, the fungus in the soil was not able to easily colonize from soil to root. On the contrary, colonization achieved in a short time under similar C/N ratio. It is considered that these results would be more remarkable for the potential on disease appearance.
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  • The Effect of Feeder Root Diseases on Crop Productivity
    Hiromitsu FURUYA
    Article type: Article
    1989 Volume 34 Pages 19-28
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_19
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    Fungal diseases which cause necrosis and/or rot in feeder roots of plants, should have more substantial effects on crop productivity than is commonly thought. Several morphological and physiological features of feeder roots which are necessary for water and nutrient uptake from the soil make themselves very susceptible to parasitic fungi. Most fungi involved in the diseases of feeder roots are soil inhabitant and exist in a wide range of soils as decomposers of plant roots. Thus, feeder roots and probably other subterranean organs of plants may generally be under some sort of physiological stress arising from the decoriaposition by weakly prasitic root infecting fungi through their life cycle. Feeder root pathogens of rice plants, including Pythium sp (p)., were isolated from a paddy field, suggesting that they may cause some damage and/or be a limiting factor of rice yield. Some possible defence strategies of plants against feeder root diseases are discussed.
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  • Soil Environment in Relation to the Incidence of Aphanomyces Root Rot of Spinach
    Kazutaka AKASHI
    Article type: Article
    1989 Volume 34 Pages 29-39
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_29
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    Root rot of spinach is a soil-borne disease caused by Aphanomyes cochlioides DRECHSLER. Effects of soil environment on the incidence of this disease were analyzed based on surveys and experiments (in vitro). It was recognized that soil moisture promoted disease outbreaks asfollows: Heavy moisture associated with rainfall or excess irrigation promotes the physiological production of zoospores of A. cochlioides and is conducive to the transmission of secondary zoospores. Due to leaching and dilution by retained water, heavy moisture also causes a decrease in the mineral salt concentration, especially nitrate nitrogen that is responsible for the inhibition of zoospore production from mycelia, the encystment and death of secondary zoospores. Consequently, the inoculum potential remains high, and outbreaks occur. Severe outbreaks occur in the fields with sandy soil where nitrate nitrogen is readily leached, with heavy clay soil or packed subsoil where nitrate nitrogen concentration is readily diluted by retained water. In addition, it is possible that the mechanisms of outbreaks of spinach root rot mentioned above apply to the diseases caused by some zoosporic fungi ; A. euteiches and Pythium aphanidermatum.
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  • Effects of Cropping Systems and Application of Organic Materials on Root Growth and Rhizosphere Microflora of Upland Crops
    Tsuneo NITTA, Tadao KON, Kenji KATAOKA, Tatsuhiko MATSUGUCHI
    Article type: Article
    1989 Volume 34 Pages 41-49
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_41
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    Effects of cropping systems and application of organic materials on root growth and rhizosphere microflora with emphasis on the root mycoflora in relation to incidence of soil-borne diseases were investigated. Organic materials such as farmyard manure, bark compost and crop residues stimulated root development, promoted lateral root growth and increased crop yields. Root mycoflora differed among the rotation and monocropping plots, as well as among the plots with and without application of organic materials. The application of organic materials increased the diversity of root mycoflora in all the plants examined. Indices of diversity were correlated with the root biomass in all the plants, which suggests that the larger the index of diversity, the greater the root growth. Furthermore the diversity of the root mycoflora was negatively correlated with the incidence of soil-borne diseases. These results suggest that the application of organic materials increased the microbiostasis of the rhizosphere ecosystem, resulting in (1) reduction of root infection with pathogens, (2) enhancement of both growth and activity of roots, and (3) increase in crop yields. Relationship between the root mycoflora of a preceding crop and the following crops in monocropping and rotation plots were examined. There were similarities in the mycoflora of the residual roots of the preceding crops and early growing roots of the succeeding crops. It is concluded that the root mycoflora significantly depends not only on organic amendments but also on the mycoflora of preceding crops through the persistence on the residual roots.
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  • Amylase Production and Pathogenicity of Ustilago crus-galli and its Leucine-Requiring Mutant
    Tatsuaki TOKUYAMA, Tsutomu KANEHIRA, Reiji TAKAHASHI, Masayuki SHINOHA ...
    Article type: Article
    1989 Volume 34 Pages 51-58
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_51
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    The smut fungus of barnyard millet, Ustilago crus-galli, Soll and its leucine-requiring mutant,SollLEU were studied in relation to amylase production and pathogenicity. The following results were obtained. The optimum nitrogen source for the growth of Soll was yeast extract and the optimum carbon source was fructose. Soluble starch was utilized as efficiently as glucose. Treatment of Soll with NTG (N-methyl-N'-nitro-N-nitrosoguanidine) induced the formation of a leucine-requiring mutant. This mutant was further treated with SDS (sodium dodecyl sulfate) -acridine orange and a stabilized SollLEU was obtained. Optimum nitrogen and carbon sources for the growth of SollLEU were identical with those of Soll. The utilization of starch, however, was considerably less efficient. Attempts were made to detect the extracellular enzymes produced by Soll and SollLEU using plated colonies. Soll produced amylase unlike SollLEU. The pathogenicity test revealed that the pathogenicity inherent to Soll had been lost in SollLEU. The amylase produced by Soll was a liquefying α-amylase with high activity in a culture medium containing yeast extract. This amylase exhibited a considerably different degrading activity on six kinds of raw starch. SollLEU, on the other hand, exhibited a low amylase activity.
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  • [title in Japanese]
    Kazuhiro HOSHI, Tomio YOSHIDA
    Article type: Article
    1989 Volume 34 Pages 59-63
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_59
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    The presence of oxygen may affect the nitrogenase activity of nitrogen-fixing bacteria. The effect of oxygen concentration on the acetylene reducing activity (ARA) of nitrogen-fixing bacteria Enterobacter, Azospirillum, Pseudomonas, Xanthobacter and Alcaligenes associated with rice roots cultivated in paddy soils in Japan was investigated. The following results were obtained : 1) The oxygen concentration inducing maximum nitrogenase activity was 2.0, 2.0, 0.8, 0.3, and 1.0 KPa for Enterobacter, Azospirillum, Pseudomonas, Xanthobacter and Alcaligenes, respectively. 2) Nitrogenase activity was not limited at 5.0 KPaO_2 for Enterobacter and Azospirillum, but limited at 5.0 KPaO_2 for Pseudomonas, Xanthobacter and Alcaligenes. In the complete anaerobic condition, the nitrogenase activity was not detected in any of the bacterial strains used in this study. 3) Enterobacter, Azospirillum and Xanthobacter showed a broad spectrum for the effect of oxygen on the nitrogenase activity, while Pseudomonas and Alcaligenes showed a narrow spectrum.
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  • Charcoal as a Possible Inoculation Carrier for VA Mycorrhizal Fungi
    Masanori SAITO
    Article type: Article
    1989 Volume 34 Pages 65-68
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_65
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  • [title in Japanese]
    [in Japanese]
    Article type: Article
    1989 Volume 34 Pages 69-
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_69_1
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  • [title in Japanese]
    [in Japanese]
    Article type: Article
    1989 Volume 34 Pages 69-70
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_69_2
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  • [title in Japanese]
    [in Japanese]
    Article type: Article
    1989 Volume 34 Pages 70-
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_70_1
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  • [title in Japanese]
    [in Japanese]
    Article type: Article
    1989 Volume 34 Pages 70-71
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_70_2
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  • [title in Japanese]
    [in Japanese]
    Article type: Article
    1989 Volume 34 Pages 71-72
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_71
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  • [title in Japanese]
    [in Japanese]
    Article type: Article
    1989 Volume 34 Pages 72-73
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_72
    JOURNAL FREE ACCESS
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  • [title in Japanese]
    [in Japanese]
    Article type: Article
    1989 Volume 34 Pages 73-74
    Published: November 01, 1989
    Released on J-STAGE: May 31, 2017
    DOIhttps://doi.org/10.18946/jssm.34.0_73
    JOURNAL FREE ACCESS
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