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Research has been conducted on the interactions among Spartina patens and the sediment microbial populations during the growing season. The analysis of the arbuscular mycorrhizal fungi has been carried out and the results indicate that the fungi increase the nutrient supply to the host plant and affect soil microbial populations.

Researchers show that soil can be inoculated with strains of the actinomycete Frankia that are high nitrogen fixers in the absence of the host plant and the strain will maintain its nitrogen-fixing ability. These strains can successfully compete with the indigenous Frankia species and form nodules that increase plant growth.

Results show that there is not much complexity in the populations of sulfate-reducing bacteria which exhibit similar hybridization values suggesting an interaction between the two groups of bacteria.

Research is conducted on the use of molecular and cultivation techniques to identify the number of the dominant bacteria in anoxic rice soil. Population sizes determined by liquid dilution cultures and isolated microorganisms from terminal dilution steps are examined.

The phototrophic sulfur bacteria populations found in the chemocline of Lake Cadagno in Switzerland has been studied by molecular methods. A combination of 16S rRNA and 16S ribosomal DNA sequence analysis were used in analyzing the bacterial communities. Results indicated the presence of a number of phototrophic sulfur bacteria. Strains Chromatium okenii DSM169, Amoebabacter purpureus DSM4197 and Lamprocystis roseopersicina DSM229 were detected.

An aquifer contaminated with diesel fuel was bioremediated in situ by the introduction of oxidants such as O2 and NO3- and nutrients to stimulate microbial activity. An aquifer sample was extracted after 3.5 years of remediation to determine bacterial strains which can flourish on selected hydrocarbons under denitrifying conditions, create a laboratory aquifer column to induce the aerobic and denitrifying processes.

Whole-cell hybridization with digoxigenin-labeled in vitro transcripts followed by an antibody-alkaline phosphatase detection of the digoxigenin reporter molecular helped trace the mRNA of the thiostrepton resistance gene (tsr) harbored by plasmid PIJ673 in streptomyces violacelatus. Before hybridization, the cells had to be permeabilized by lysozyme, the detergent Nonidet P-40 and toulene. Hybridization with digoxigenin-labeled, 16S rRNA-targeted oligonucleotides indicated the permeability of the Streptomyces violacelatus cells for probes and the antibody-alkaline phosphatase conjugate.

Frankia strains in pure cultures and in nodules is detected and identified by the use of whole-cell hybridization with non-radioactively labeled oligonucleotide probes. After the removal of the polysaccharide capsule surrounding the vesicles, identification of Frankia vesicles in nodule homogenates is possible. Specific hybridization is facilitated by incubation with H2O2 (15% in water for 1 h at room temperature) before lyzozyme and detergent treatments.

The possibility of utilizing fluorescently labelled oligonucleotides targeted against rRNA for the in situ detection of soil microorganisms was assessed. Initial experiments were carried out to determine if the procedure could detect, with minimal background activity, inoculated samples of Pseudomonas aeruginosa. The results showed minimal background activity due to organic matter, although the optimal bacterial recovery was not achieved. Species-specific probes could detect artificially spiked soil samples, however, the method was not effective in monitoring natural bacterial soil populations.

Several comparative sequence analyses are conducted to explain the diversity observed in the Frankia populations present in the root nodules of Alnus oblongifolia, the tress found in central Arizona. The sequences are shown to exhibit extremely high diversity.

The development of a molecular tool to target nitrogen-fixing bacteria with sequence similarities to members of the [epsi] subclass of Proteobacteria is reported. The specificity of the primer set is confirmed by the retrieval of nifH sequences of only putative members of the [epsi] subclass.