Cyanobacteria were among the pioneer organisms of the early earth. They first colonized bare rock and had a strong ability to proliferate in infertile substrates, such as volcanic ash, desert sand, and rock. Cyanobacteria store enormous amounts of essential nutrients and metabolites within their cytoplasm. Those that grow in arid lands can be a very potent source of organic matter and nutrients that can be used to counteract desertification. In this study, we explored the potentiality of cyanobacterial strains collected from several regions of Asia (7 strains), Africa (3 strains), and Japan (6 strains). Some of the soils had salinity levels greater than 5 dS m-1 and an alkaline pH of 8.3-9.2. Cyanobacterial strains were screened for their potential to survive in such arid soils by quantifying individual salinity tolerance, ability to fix N2 in a medium containing 0.1M NaCl, and rates of photosynthesis and growth. The inoculation effects on the chemical properties of Alashan soils of Inner Mongolia (China) were evaluated using AL-S and Tateyama cyanobacterial strains. The soil pH of the surface and subsurface layers indicated that these strains can decrease pH to levels that are conducive to plant growth. These cyanobacterial strains have potential as anti-desertification agents for the bioreclamation of arid soils.

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The ability of soil microorganisms to decolorize Reactive Red 141, an industrial textile dye used commonly in Southeast Asia, including Thailand, was analyzed. Incubation experiments showed that the dye was decolorized under a static anoxic condition of liquid medium inoculated with soil microorganisms, while it was not decolorized in a shaking aerobic condition. Fourteen isolated bacteria that decolorize the dye were identified and found to belong to Gram-positive bacteria, such as Bacillus, and Gram-negative bacteria, such as Stenotrophomonas. Attenuated total reflectance fourier transform infrared (ATR-FTIR) analysis suggested that the intermediate products of degradation of the dye were naphthalene derivatives and other smaller compounds produced by oxidative cleavage of the dye, irrespective of the difference of the strains. Together with the variety of the phylogenetic locations of the isolated strains, this suggested that the reaction is catalyzed by non-specific enzyme(s) under an anoxic condition.

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The effects of large-quantity applications of N, P, K, Ca, or Mg or a compound of these five components on soil microbial biomass (biomass) and soil microbial respiratory activity (respiratory activity) were investigated. It was found that the microbial biomass and the respiratory activity were affected by both the quantity and the kind of element. The biomass in the P-, K-, Ca-, or Mg-treatment was not significantly different from that in non-fertilizer treatment. However, the biomass showed the maximum value in the compound treatment with 5 times the standard fertilizer level. The biomass tended to increase with the increase of the soil EC and did not decrease even with a high EC of 3 mS cm^<-1>. On the other hand, the respiratory activity decreased with an increase of the soil EC and remained at a low level under conditions of more than 1.0 mS cm^<-1>. Most fertilizer salts contained sulfate as an associated element. The relationship between the amount of sulfate application and the respiratory activity resembled that between EC and the respiratory activity. The respiratory activity remained at a low level under conditions of more than 2,000 mg kg^<-1> of sulfate. Thus, the respiratory activity decreased with an increase in the salt concentration, and EC or sulfate values that decreased the respiratory activity were almost the same as or somewhat higher than those recommended as a result of common soil diagnosis.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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