RESUMO
AIMS: To combine molecular and cultivation techniques to characterize the methanotrophic community in the soil-water interface (SWI) and rhizospheric soil from flooded rice fields in Uruguay, a temperate region in South America. METHODS AND RESULTS: A novel type I, related to the genus Methylococcus, and three type II methanotrophs were isolated from the highest positive dilution steps from the most probable number (MPN) counts. Potential methane oxidation activities measured in slurried samples were higher in the rhizospheric soil compared to the SWI and were stimulated by N-fertilization. PmoA (particulate methane monooxygenase) clone libraries were constructed for both rice microsites. SWI clones clustered in six groups related to cultivated and uncultivated members from different ecosystems of the genera Methylobacter, Methylomonas, Methylococcus and a novel type I sublineage while cultivation and T-RFLP (terminal restriction fragment length polymorphism) analysis confirmed the presence of type II methanotrophs. CONCLUSIONS: Cultivation techniques, cloning analysis and T-RFLP fingerprinting of the pmoA gene revealed a diverse methanotrophic community in the rice rhizospheric soil and SWI. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reports, for the first time, the analysis of the methanotrophic diversity in rice SWI and this diversity may be exploited in reducing methane emissions.
Assuntos
Variação Genética , Methylococcaceae/classificação , Oryza , Raízes de Plantas/microbiologia , Microbiologia do Solo , DNA Bacteriano/análise , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Inundações , Metano/metabolismo , Methylococcaceae/genética , Methylococcaceae/isolamento & purificação , Oxigenases , Filogenia , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 16S/genéticaRESUMO
Sterols (e.g. cholesterol) present in wool scouring effluent represent the most recalcitrant fraction in anaerobic treatment. This study was conducted to examine the feasibility of removal of this organic load through a denitrifying post-treatment stage. A stable cholesterol-denitrifying enrichment (CHOL-1) was obtained from sludge of a bench-scale upflow sludge bed (USB) denitrifying reactor integrated to a carbon and nitrogen removal system for sanitary landfill leachate. According to the amounts of cholesterol degraded and of nitrite and nitrogen gas formed, the capacity for complete cholesterol oxidation under anaerobic conditions by CHOL-1 can be assumed. Nitrite accumulation observed at a low C/N ratio outlines the importance of determining the optimal C/N ratio for adequate denitrifying reactor performance. The enrichment was partly identified with molecular analysis of cloned 16S rDNA sequences revealing the presence of two groups of bacteria belonging to the beta subclass of the Proteobacteria. According to analysis of sequences, it can be inferred that a yet uncultivated new bacterium is the one responsible for cholesterol oxidation. Results of this study suggest that sludge from a denitrifying reactor treating leachate is potentially useful in a combined anaerobic-anoxic system for degradation of cholesterol that remains after methanogenic treatment.
Assuntos
Bactérias Anaeróbias/fisiologia , Colesterol/metabolismo , Eliminação de Resíduos/métodos , Hipóxia , Nitratos/análise , Nitritos/análise , Nitrogênio/análise , Nitrogênio/metabolismo , Oxirredução , RNA Ribossômico 16S/análiseRESUMO
A new moderately thermophilic proteolytic anaerobe, strain UT, was isolated from mesophilic granular methanogenic sludge. The cells were spore-forming, motile rods that were 0.4 micron wide and 2.4 to 4 microns long and stained gram negative. Electron micrographs of thin sections revealed the presence of an atypical gram-positive cell wall. Optimum growth occurred at 55 degrees C and at pH values between 7.0 and 7.5, with a doubling time of 30 min. The DNA base ratio of guanine plus cytosine was 31 mol%. The bacterium fermented proteins mainly to acetate, hydrogen, formate, and branched-chain fatty acids. Several amino acids, including glutamate, aspartate, arginine, histidine, threonine, methionine, and branched-chain amino acids, were also utilized. Glutamate was degraded to acetate, formate, hydrogen, and alanine. In addition, the strain degraded carbohydrates, including glucose, fructose, mannose, cellobiose, and starch, to acetate, ethanol, formate, lactate, and hydrogen. The results of a 16S rRNA sequence analysis phylogenetically placed strain UT in the low-guanine-plus-cytosine-content subgroup of the gram-positive phylum. We propose to classify the described strain in the genus Caloramator as a new species, Caloramator proteoclasticus. The type strain of C. proteoclasticus, strain U, has been deposited in the Deutsche Sammlung von Mikroorganismen as strain DSM 10124.
Assuntos
Bactérias Anaeróbias/classificação , Bactérias Anaeróbias/genética , Esgotos/microbiologia , Bactérias Anaeróbias/ultraestrutura , Proteínas de Bactérias/metabolismo , Divisão Celular , DNA Bacteriano/análise , Fermentação , Temperatura Alta , Microscopia Eletrônica , Dados de Sequência Molecular , Filogenia , RNA Ribossômico 16S/análiseRESUMO
The sludge of an anaerobic lagoon treating the wastewater from a factory producing baker's yeast was evaluated as inoculum for anaerobic digestion. Specific methanogenic activity tests failed to give a good estimation of the trophic groups that were evidenced by enumerations involving Most Probable Number estimations. This failure was ascribed to the toxic effects of either the acetate concentrations used or to the ammonia content of the sludge.