In order to estimate the effect of heavy metal pollution on soil microorganisms, a field survey was carried out in a heavy-metal-contaminated (Cd, 1.1-2.7 rag/ kg soil; Zn, 234-571 mg/kg soil; Cu, 310-751 mg/kg soil) fallow paddy field. Although the number of actinomycetes and bacteria decreased significantly with increasing heavy metal content, there was no significant correlation between the number of fungi and heavy metal content. Actinomyeetes were affected by heavy metals most strongly. The degree of tolerance to heavy metals appears to be: fungi>bacteria>aetinomycetes. These results suggest that the relatively low concentrations of heavy metals in the research area affected the soil microbial population.
Twenty-eight axenio planktonic cyanobacterial strains (10 Microcystis, three Osciiiatoria, one Spiruiina, one Aphanizomenon, 13 Anabaena) were investigated for their fatty acid composition by measurement of nonpolar and hydroxy fatty acids. No 2-hydroxy fatty acids were detected in any strain, but 3-hydroxy fatty acids were detected in minor quantities in 24 strains. The highest portion of total fatty acids were non-polar fatty acids. Qualitative and quantitative analyses of 3-hydroxy fatty acids showed no taxonomic value in these strains, while the type of non-polar fatty acid composition was shown to be consistent within Microcystis and Anabaena strains, distinguishing them as type 4, characterized by the presence of 18:4, and type 2, characterized by 18;3 (a) of the Kenyon-Murata system. Two Osciiiatoria agardhii Gomont strains were also included in the type 2 group due to the presence of 18: 3 (a), but the difference in characteristics of 16:2 and 16:3 between 0. agardhii and Anabaena turther dmdeti type 2 into two subgroups: type 2A for Anabaena and type 2B for 0. agardhii. A simplified unweighted pair group method with arithmetic averages (UPGMA) dendrogram demonstrated that the classification of 28 strains {Microcystis spp., Anabaena spp,, Aphanizomenon fios-aquae (Lemmermann) Ralfs f. graciie (Lemmermann) Elenkin, 0. agardhii and Spiruiinasubsaisa Oersted ex Gomont based on numerical analysis of nonpolar fatty acids corresponded to morphological species criteria, suggesting that non-polar fatty acid composition is a valuable chemical marker in the taxonomy of planktonic cyanobacteria. However, the fatty acid composition in Csciiiatoria raciborskii is similar to that of Microcystis and very different from that of 0. agardhii, suggesting its special position in Osciiiatoria and the chemical diversity in the genus Osciiiatoria.
The bacterial community structure in the Changjiang estuary was studied for comparison with future changes, related to the construction of the Three Gorges Dam. Population densities of bacteria in the surface water at station C1 estimated by CFU on marine agar plates and by DAPI direct count, were 2.8 x 10(4) ml(-1) and 4.2 x 10(5) ml(-1), respectively. Physicochemical properties of water, such as temperature and salinity, suggested that station C1 was affected by freshwater from the Changjiang River. Cluster analysis of the PCR-RFLP patterns obtained from 9 samples showed that the bacterial community structure at station C1 was different from the structure at the other stations. Bacterial diversity in the surface water at station C1 was studied based on the genotypes of the 250 clones of 16S rRNA, and on the phenotypes generated on Biolog GN plates for 70 isolates. Sequences of bacteria from two common marine groups, alpha- and gamma-Proteobacteria, were frequently observed. Some other divisions, including the beta-Proteobacteria, C/F/B group, low G+C gram positive, high G+C gram positive, chloroplasts, and relatives of Verrucomicrobia were also observed. The putative dominant species based on both genotype and phenotype analyses were close relatives of Alteromonas macleodii or Roseobacter spp. These results reflected the nutrient-rich environment at station C1.
Kushiro Mire is the largest mire in Japan and in 1980 was the first wetland in Japan registered under the Ramsar Convention. Recent reports indicate an increase in nutrient loading into Kushiro Mire from changes in land use. We measured vertical profiles of dissolved inorganic nitrogen (DIN; NO 3 -, NO 2 -, NH 4 ? ), dissolved organic carbon (DOC), and various types of microbial activity in soil samples collected to approximately 1.5 m deep at two sites in Kushiro Mire. We found an accumulation of NO 3 -and DOC in the deeper soil. Denitrifying activity was highest in the shallower soils and decreased drastically with depth, whereas higher levels of fluoresceindiacetate hydrolysis, b-glucosidase, acid phosphatase, and xylosidase enzyme activity were found in the deeper layers. We also detected humic-like substances as components of the DOC. These results suggest that the DOC in the wetland soil cannot be used as a substrate for denitrification, causing denitrification to be suppressed in the deeper soil. In addition, denitrifying activity would be very low in the deeper layers due to low soil temperature. As a result, nitrogen input to the mire has resulted in a large accumulation of NO 3 -in the deeper soil. This will eventually change the mire ecosystem through effects such as increased eutrophication and acidification.
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