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The potential activity and diversity of methanotrophic bacteria in samples from forest soil, peat, and sediment from a hydroelectric reservoir (Robert-Bourassa) and lakes located in the sub-arctic taiga were studied. Incubation experiments with soil slurries, methanotrophic bacterial counts, and direct PCR amplification of genes specific to methanotrophic bacteria were carried out on soil and sediment samples from three locations (nonflooded, periodically flooded, and flooded) from the reservoir. Sediments from three lakes located near the reservoir were also sampled to compare with nearby unperturbed aquatic systems. Only the uppermost part (5-10 cm) of soils and sediments was analyzed. Regardless of the incubation temperature, potential methane (CH4) oxidation rates were lower (0.028-0.066 mol CH4g−1soil d−1) in nonflooded forest soil compared to lacustrine sediments that exhibited potential oxidation rates generally close to those observed in periodically flooded or flooded forest soil (0.04-0.14 mol CH4g−1soil d−1), but far below the range of values (0.20-0.58 mol CH4g−1soil d−1) recorded in peat systems. Samples from flooded forest soil and peat had higher CH4uptake activity, but this could not be related to a greater number of methanotrophic bacteria (pmoAprobe-positive colonies). Analysis of genes specific to methanotrophic bacteria revealed a low diversity in the methanotrophic community, with the genus Methylocystisbeing dominant. Overall, samples of flooded soil and peat with higher CH4production rates also had higher rates of CH4oxidation by methanotrophic bacteria. Flooding also seems to modify the resilience of the methanotrophic community to temperature fluctuations, an important consideration for future studies.

A rapid enrichment approach based on a pentachlorophenol (PCP) feeding strategy which linked the PCP loading rate to methane production was applied to an upflow anaerobic sludge bed reactor inoculated with anaerobic sludge. Due to this strategy, over a 140-day experimental period the PCP volumetric load increased from 2 to 65 mg LR⁻¹ day⁻¹ with a near zero effluent concentration of PCP. Dechlorination dynamics featured sequential appearance of 3,4,5-chlorophenol, 3,5-chloro- phenol, and 3-chlorophenol in the reactor effluent. Profiling of the reactor population by denaturing gradient gel electrophoresis (DGGE) revealed a correlation between the appearance of dechlorination intermediates and bands on the DGGE profile. Nucleotide sequencing of newly detected 16S rDNA fragments suggested the proliferation of Clostridium and Syntrophobacter/Syntrophomonas spp. in the reactor during PCP degradation. Published by John Wiley & Sons, Inc. Biotechnol Bioeng 73: 476–483, 2001.

To monitor the biodegradation of explosives in microcosm experiments, carbon-14 labelled substrates such as ¹⁴C-HMX were needed. Many synthetic routes were evaluated to identify the best synthesis of ¹⁴C-HMX with high yield and minimal radioactive waste. To synthesize ¹⁴C-HMX, acetylation of labelled hexamethylenetetramine (¹⁴C-HMTA) was done yielding 3,7-diacetyl-1,3,5,7-tetraazabicyclo-[3.3.1]-nonane (¹⁴C-DAPT) which was nitrated to obtain 1,5-diacetyloctahydro-3,7-dinitro-1,3,5,7-tetrazocine (¹⁴C-DADN) in one step. Nitrolysis of ¹⁴C-DADN was achieved using a mixture of 100% nitric acid and phosphorus pentoxide to yield ¹⁴C-HMX. The synthesis of this carbon-14 labelled HMX was optimized first using cold starting materials and then conducted with labelled compounds. This synthesis represents the best way of preparing high purity ¹⁴C-HMX with a high yield. Copyright © 1999 John Wiley & Sons, Ltd.

A phenanthrene-mineralizing Pseudomonas sp., designated UG14, was isolated from creosote-contaminated soil. It contained two plasmids, of approximately 77 kb and 76 kb, the smaller of which contained DNA sequences that hybridized with probes specific for ndoB and xylE, genes involved in catabolism of aromatic hydrocarbons. At initial phenanthrene concentrations of 10, 50, 200 and 1000 mg/l broth, 27%, 19%, 7.7% and 3.3%, respectively, of the [9-14C]phenanthrene was recovered as 14CO2 after 36 days' incubation at 30°C. Most 14C-label was converted to a water-soluble metabolite tentatively identified as 1-hydroxy-2-naphthoic acid. Rhamnolipid biosurfactants produced by P. aeruginosa UG2 enhanced mineralization of 50 mg phenanthrene/l by Pseudomonas sp. UG14. With the biosurfactant at 0, 25 and 250 mg rhamnose equivalents/l, 6.5%, 8.2% and 9.8%, respectively, of the phenanthrene was mineralized after 35 days.

The population density and activity of a microbial community associated with the sediment and rhizosphere of an intertidal freshwater wetland dominated by Scirpus pungens was monitored before and following the application of weathered Mesa light crude oil and fertilizers. The influence of nutrient enrichment (fertilizers) and plant growth on oil degradation rates was determined from the resulting data. The study plots (four blocks of replicates) were subjected to five treatments: oil only (natural attenuation); oil plus ammonium nitrate and phosphate, with regular cropping of the plants; oil plus ammonium nitrate and phosphate; oil plus sodium nitrate and phosphate; no oil, ammonium nitrate and phosphate. The plots were regularly monitored in the field for gas production (carbon dioxide and nitrous oxide), and samples were collected for laboratory analysis of denitrification activity, aliphatic and aromatic hydrocarbon degradation activity, and total heteroptrophic bacteria. The viable bacterial population density increased during the first 4 weeks in oiled and unoiled experimental plots that were fertilized. In contrast, population densities in untreated areas remained relatively unchanged throughout the monitoring period. The microbial population demonstrated a rapid and sustained increase in naphthalene mineralization activity in plots that were both fertilized and oiled. Hexadecane mineralization activity increased in response to fertilizer application, with ammonium nitrate causing a larger increase than sodium nitrate. A very significant difference observed in the mineralization of hexadecane was that the surface sediments were much more active than the subsurface sediments. This difference became even more pronounced in the second year of monitoring, even though the treatment regime had been discontinued. This compartmentalization of mineralization activity was not observed for naphthalene. Following fertilizer application, field and laboratory evaluation of nitrogen metabolism in the sediments indicated significant denitrification activity that was not adversely affected by oiling. The results demonstrated that the application of fertilizers stimulated the activities of indigenous hydrocarbon-degrading and denitrifying bacteria, and the presence of oil either enhanced or had no detrimental effect on these activities. As a remediation strategy, the application of fertilizers to a wetland shoreline following an oil spill would promote the growth of indigenous plants and their associated microbial flora, resulting in increased metabolic activity and the potential for increased oil degradation activity.