RESUMEN
Methanol-oxidizing bacteria may play an important role in the development and use of biological treatment systems for the removal of methanol from industrial effluents. Optimization of methanol degradation potential in such systems is contingent on availability of nutrients, such as nitrogen, in the most favorable form and concentration. To that end, this study examined the variation in growth, methanol degradation, and bacterial diversity of two mixed methylotrophic cultures that were provided nitrogen either as ammonium or nitrate and in three different concentrations. Methanol-degrading cultures were enriched from biofilms sampled at a pulp and paper mill and grown in liquid batch culture with methanol as the only carbon source and either ammonium or nitrate as the only added nitrogen source. Results indicate that growth and methanol removal of the mixed cultures increase directly with increased nitrogen, added in either form. However, methanol removal and bacterial diversity, as observed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) methods, were higher when using nitrate as the nitrogen source for enrichment and growth, rather than ammonium. Based on results described here, nitrate may potentially be a better nitrogen source when enriching or working with mixed methylotrophic cultures, and possibly more effective when used as a nutrient addition to biofilters.
Asunto(s)
Bacterias/genética , Bacterias/metabolismo , Biopelículas/crecimiento & desarrollo , Metanol/metabolismo , Nitrógeno/metabolismo , Papel , Bacterias/clasificación , Electroforesis en Gel de Gradiente Desnaturalizante , Variación Genética/genética , Residuos Industriales , Oxidación-Reducción , Reacción en Cadena de la PolimerasaRESUMEN
Motivated by the need to establish an economical and environmentally friendly methanol control technology for the pulp and paper industry, a bench-scale activated carbon biofiltration system was developed. This system was evaluated for its performance in removing methanol from an artificially contaminated air stream and characterized for its bacterial diversity over time, under varied methanol loading rates, and in different spatial regions of the filter. The biofilter system, composed of a novel packing mixture, provided an excellent support for growth and activity of methanol-degrading bacteria, resulting in approximately 100% methanol removal efficiency for loading rates of 1-17 g/m(3) packing/h, when operated both with and without inoculum containing enriched methanol-degrading bacteria. Although bacterial diversity and abundance varied over the length of the biofilter, the populations present rapidly formed a stable community that was maintained over the entire 138-day operation of the system and through variable operating conditions, as observed by PCR-DGGE methods that targeted all bacteria as well as specific methanol-oxidizing microorganisms. Phylogenetic analysis of bands excised and sequenced from DGGE gels indicated that the biofilter system supported a diverse community of methanol-degrading bacteria, with high similarity to species in the genera Methylophilus (beta-proteobacteria), Hyphomicrobium and Methylocella (both alpha-proteobacteria).
Asunto(s)
Bacterias/genética , Biodiversidad , Carbón Orgánico/química , Filtración/instrumentación , Metanol/aislamiento & purificación , Bacterias/crecimiento & desarrollo , Biodegradación Ambiental , Recuento de Colonia Microbiana , Medios de Cultivo , ADN Bacteriano/genética , Filogenia , ARN Ribosómico 16S/genéticaRESUMEN
Strain CSC1(T), a Gram-negative, aerobic, methane-oxidizing bacterium, was isolated from an uncontaminated aquifer nearly 20 years ago. Based on 16S rRNA gene sequence similarity, this strain was identified as a member of the Alphaproteobacteria, most closely related to an uncultured member of the Methylocystaceae as well as two cultured organisms, Methylocystis sp. L32 and Methylocystis sp. SC2. This strain differed from extant species in cell shape, size, expression of soluble methane monooxygenase and its unique spiny surface layers, composed of polysaccharide. DNA-DNA hybridization results showed only 3.8 % relatedness with Methylocystis echinoides NCIMB 13100 and 41.1 % relatedness with Methylocystis rosea SV97(T). Based on these genotypic and physiological differences, this isolate is proposed as a member of a novel species of the genus Methylocystis, Methylocystis hirsuta sp. nov. (type strain CSC1(T) =ATCC BAA-1344(T) =DSM 18500(T)).
Asunto(s)
Agua Dulce/microbiología , Methylocystaceae/clasificación , Methylocystaceae/aislamiento & purificación , ADN Bacteriano/genética , ADN Ribosómico/genética , Methylocystaceae/genética , Datos de Secuencia Molecular , Filogenia , ARN Ribosómico 16S/genéticaRESUMEN
With increased application of co-solvent flushing technologies for removal of nonaqueous phase liquids from groundwater aquifers, concern over the effects of the solvent on native microorganisms and their ability to degrade residual contaminant has also arisen. This study assessed the impact of ethanol flushing on the numbers and activity potentials of trichloroethylene (TCE)-degrading microbial populations present in aquifer soils taken immediately after and 2 years after ethanol flushing of a former dry cleaners site. Polymerase chain reaction analysis revealed soluble methane monooxygenase genes in methanotrophic enrichments, and 16S rRNA analysis identified Methylocystis parvus with 98% similarity, further indicating the presence of a type II methanotroph. Dissimilatory sulfite reductase genes in sulfate-reducing enrichments prepared were also observed. Ethanol flushing was simulated in columns packed with uncontaminated soils from the dry cleaners site that were dosed with TCE at concentrations observed in the field; after flushing, the columns were subjected to a continuous flow of 500 pore volumes of groundwater per week. Total acridine orange direct cell counts of the flushed and nonflushed soils decreased over the 15-week testing period, but after 5 weeks, the flushed soils maintained higher cell counts than the nonflushed soils. Inhibition of methanogenesis by sulfate reduction was observed in all column soils, as was increasing removal of total methane by soils incubated under methanotrophic conditions. These results showed that impacts of ethanol were not as severe as anticipated and imply that ethanol may mitigate the toxicity of TCE to the microorganisms.
Asunto(s)
Etanol/farmacología , Contaminantes del Suelo/metabolismo , Solventes/metabolismo , Tricloroetileno/metabolismo , Bacterias/genética , Bacterias/crecimiento & desarrollo , Biodegradación Ambiental , Reacción en Cadena de la Polimerasa , ARN Ribosómico 16S/análisis , Microbiología del Suelo , Administración de Residuos , Movimientos del AguaRESUMEN
2-Methylisoborneol (MIB), a metabolite of blue-green algae, has been implicated in causing unpalatable drinking water throughout the world. Current non-biological water treatment technologies are ineffective in removing MIB from potable water or are cost-prohibitive, and biological applications may address these problems. We have isolated and characterized a bacterium derived from lake water and capable of aerobically degrading MIB. Light microscopy and transmission electron microscopy revealed that this strain is a spore-forming, flagellated bacterium that is bacilloid in shape, and 16S rRNA phylogenetic analysis determined that it is most closely related to Bacillus fusiformis and Bacillus sphaericus, both members of the Bacillus sphaericus senso lato taxon. While the growth and oxidation potential of this strain was shown to be affected beyond certain MIB concentrations in the mg/l range, it was capable of depleting MIB at mg/l and ng/l concentrations and of removing MIB to concentrations yielding no observed odor.
Asunto(s)
Bacillus/fisiología , Canfanos/aislamiento & purificación , Odorantes/prevención & control , Purificación del Agua/métodos , Bacillus/genética , Bacillus/crecimiento & desarrollo , Biodegradación Ambiental , Canfanos/análisis , Canfanos/metabolismo , ADN Bacteriano/análisis , Odorantes/análisis , Filogenia , ARN Ribosómico 16S/análisis , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/aislamiento & purificación , Contaminantes Químicos del Agua/metabolismoRESUMEN
Methanotrophs, bacteria that thrive in the presence of stable methane and oxygen concentrations, can cometabolically oxidize ortho-substituted biphenyls to yield a variety of hydroxylated products. Despite awareness of the susceptibility of ortho-substituted biphenyls and other aromatic compounds to methanotrophic oxidation, the molecular properties relevant for predicting rates of methanotrophic oxidation are unknown. To this end, we have developed quantitative structure-biodegradation relationships using oxygen uptake activity by the type 2 methanotroph. Methylosinus trichosporium OB3b, expressing the soluble form of methane monooxygenase and in the presence of nine ortho-substituted biphenyls. Multivariate analysis yielded the strongest correlations using the initial slope of the oxygen uptake rate versus substrate concentration curve as the dependent variable. Quantum mechanical descriptors, including the sum of carbon charges on the substituted ring, the charge on the substituted carbon, and the width of compound calculated using computationally derived bond lengths and dihedral angles, correlated more strongly with oxygen uptake activity than did empirically derived electronic descriptors. The resulting models suggest a significant influence of substituent electronic nature and size and the involvement of the substituted carbon site in the oxidation of these compounds by M. trichosporium OB3b.
Asunto(s)
Contaminantes Ambientales/metabolismo , Methylosinus trichosporium/enzimología , Methylosinus trichosporium/genética , Oxigenasas/farmacología , Bifenilos Policlorados/metabolismo , Biodegradación Ambiental , Oxidación-Reducción , Relación Estructura-Actividad CuantitativaRESUMEN
In a commitment to zero ozone depletion, the United Nations and the U.S. Environmental Protection Agency (EPA) have called for the phase-out of the manufacture and import of hydrochlorofluorocarbons (HCFCs), used as auxiliary blowing agents (ABAs) in the manufacture of polyurethane foams. As a result, more environmentally benign alternative ABAs are being sought by the foam-blowing industry. This study examined the life cycle of HCFC-22, hydrofluorocarbon-134a (HFC-134a), and cyclopentane, which are currently used or considered as potential alternative ABAs in the manufacture of rigid polyurethane foams that serve as insulation in a model North American refrigerator. The raw material extraction/refining, manufacturing, use, and disposal stages of the life cycle of each ABA were considered, and their resulting relative impacts on ozone depletion and global warming were compared. The manufacturing, use, and disposal stages were determined to affect ozone depletion and global warming to the largest extent, emphasizing the need for a greater focus on pollution prevention opportunities in these stages. The HFC-134a life cycle yields no impact on ozone depletion and a significantly decreased global warming impact compared with its predecessor, HCFC-22, and a tradeoff of slightly higher global warming impact and fewer added safety concerns compared with its more flammable counterpart, cyclopentane.