High-performance liquid chromatography (HPLC) with an anion-exchange nonporous column was used to analyze restriction fragment length polymorphism (RFLP) of the 16S ribosomal DNA (rDNA) of scum-forming actinomycetes found in three different activated sludge plants. 16S rDNA fragments from washed scum samples were amplified by PCR and cloned into plasmid vectors. The 16S rDNA inserts in the plasmids were reamplified in vitro, cut with restriction endonucleases, and separated directly by HPLC. Compared to conventional agarose electrophoresis, the HPLC system used allowed better separation of fragments up to 500bp. The HPLC-RFLP patterns of the scum clones were compared with those of PCR-amplified 16S rDNAs from authentic strains and with computer-predicted restriction patterns of the available 16S rDNA data on the actinomycetes. 16S rDNA-RFLP comparisons indicated that the predominat scum-forming bacteria were Gordona amarae in two activated sludge plants and Rhodococcus sp. in the remaining one. These findings agreed well with results of lipoquinone profiling of the scum performed concurrently. The results of this study indicated that a combination of 16S rDNA-RFLP analysis and quinone profiling should provide a more powerful non-cultivating tool for the identification of scum-forming bacteria in activated sludge.
The effects of infection with two ectomycorrhizal fungi, Suillus luteus and Gomphidius viscidus, on the growth and drought-tolerance of Pinus tabulaeformis (Chinese pine) seedlings under water stress conditions were examined. The growth of plants inoculated with the mycorrhizal fungi was consistently greater than that of nonmycorrhizal plants. Six months after inoculation, dry weight of mycorrhizal plants was about 2.1 times greater. Under water stress condition, net photosynthesis rate, needle water potential, and water use efficiency of mycorrhizal plant increased significantly. From these experiments, growth and drought-resistance of P. tabulaeformis were shown to be enhanced significantly by infection with the mycorrhizal fungi. The ability of 3 fungi including Cenococcum graniforme to grow under conditions of low water potential was tested in pure culture. C. graniforme and S. luteus showed negligible growth with water potentials lower than -2.0MPa. However, G. viscidus continued to grow at -2.0MPa. All of the mycorrhizal fungi showed maximum growth at -0.5MPa.
Oligotrophic bacteria, Chromobacterium sp. Y95 and Aeromonas sp. Z06, can grow in 104-diluted nutrient broth (1/104NB). In the two oligotrophic bacteria, the stationary phase cultures showed enhanced heat, oxidation, and osmotic resistance as compared with cultures at exponential phase, although resistance was less marked than that of Escherichia coli. On Southern bloting analysis, Chromobacterium sp. Y95 and Aeromonas sp. Z06 genomic DNA hybridized with the sigma factor probes, RpoN-X and RpoD-4.2, and RpoD-4.2, respectively.