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  • 1
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Oligonucleotide probes targeting ribosomal RNA can be designed with high specificity to target microbial populations at different phylogenetic levels if the cellular abundance of ribosomal RNA is sufficiently high. In contrast, polyclonal antibody probes cannot be produced with the same specificity for various phylogenetic groups, but they have the potential to detect slow growing microorganisms, populations with low metabolic activities, or even non-viable cells. We combined a polyclonal antibody stain with a ribosomal RNA targeted oligonucleotide probe for the single cell detection of species of the genus Gordona. Gordona species typically require long generation times, often exhibit filamentous growth, and are commonly encountered in activated sludge foams. Our results suggest that the ribosomal RNA content of individual cells of Gordona in activated sludge is highly variable. Therefore, the combined use of an immunostain and an oligonucleotide probe targeting ribosomal RNA can determine the identity of single cells and provide an approximation of their activity. This approach should result in improved detection limits while maintaining high specificity.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The microbial community structure of the gastrointestinal (GI) tracts of various domestic animals (bovine, ovine, caprine, and swine) was evaluated using oligonucleotide probes targeting the small subunit (SSU) ribosomal RNA (rRNA) of major microbial groups. Bacterial, eukaryotic, and archaeal rRNAs were estimated to account for approximately 60–90%, 3–30% and 0.5–3%, respectively, of the total rRNA present in the GI tracts of most of the animals examined in this study. The abundance of phylogenetically defined groups of methanogens and sulfate-reducing bacteria (SRB) was also evaluated. Methanobacteriales were the predominant methanogens in the rumen of bovine and caprine, while Methanomicrobiales predominated in the ovine rumen. A dominant archaeal group could not be identified in other sampling locations of the GI tract of these ruminants and in the GI tract of pigs, using the available collection of group-specific probes. Desulfovibrio species were the most abundant Gram-negative SRB targeted by available probes in the GI tract of nearly all animals.
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  • 3
    ISSN: 0006-3592
    Keywords: methanogenic population dynamics ; anaerobic digesters ; solid waste ; biosolids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An aggressive start-up strategy was used to initiate codigestion in two anaerobic, continuously mixed bench-top reactors at mesophilic (37°C) and thermophilic (55°C) conditions. The digesters were inoculated with mesophilic anaerobic sewage sludge and cattle manure and were fed a mixture of simulated municipal solid waste and biosolids in proportions that reflect U.S. production rates. The design organic loading rate was 3.1 kg volatile solids/m3/day and the retention time was 20 days. Ribosomal RNA-targeted oligonucleotide probes were used to determine the methanogenic community structure in the inocula and the digesters. Chemical analyses were performed to evaluate digester performance. The aggressive start-up strategy was successful for the thermophilic reactor, despite the use of a mesophilic inoculum. After a short start-up period (20 days), stable performance was observed with high gas production rates (1.52 m3/m3/day), high levels of methane in the biogas (59%), and substantial volatile solids (54%) and cellulose (58%) removals. In contrast, the mesophilic digester did not respond favorably to the start-up method. The concentrations of volatile fatty acids increased dramatically and pH control was difficult. After several weeks of operation, the mesophilic digester became more stable, but propionate levels remained very high. Methanogenic population dynamics correlated well with performance measures. Large fluctuations were observed in methanogenic population levels during the start-up period as volatile fatty acids accumulated and were subsequently consumed. Methanosaeta species were the most abundant methanogens in the inoculum, but their levels decreased rapidly as acetate built up. The increase in acetate levels was paralleled by an increase in Methanosarcina species abundance (up to 11.6 and 4.8% of total ribosomal RNA consisted of Methanosarcina species ribosomal RNA in mesophilic and thermophilic digesters, respectively). Methanobacteriaceae were the most abundant hydrogenotrophic methanogens in both digesters, but their levels were higher in the thermophilic digester. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 342-355 1998.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9699
    Keywords: Anaerobic digesters ; methanogens ; oligonucleotide probes ; 16s rRNA ; sulfate-reducing bacteria ; two-phase digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The microbial community structure of twenty-one single-phase and one two-phase full-scale anaerobic sewage sludge digesters was evaluated using oligonucleotide probes complementary to conserved tracts of the 16S rRNAs of phylogenetically defined groups of methanogens and sulfate-reducing bacteria. These probe results were interpreted in combination with results from traditional chemical analyses and metabolic activity assays. It was determined that methanogens in “healthy” mesophilic, single-phase sewage sludge digesters accounted for approximately 8–12% of the total community and thatMethanosarcinales andMethanomicrobiales constituted the majority of the total methanogen population.Methanobacteriales andMethanococcales played a relatively minor role in the digesters. Phylogenetic groups of mesophilic, Gram-negative sulfate-reducing bacteria were consistently present at significant levels:Desulfovibrio andDesulfobulbus spp. were the dominant sulfate-reducing populations,Desulfobacter andDesulfobacterium spp. were present at lower levels, andDesulfosarcina, Desulfococcus, andDesulfobotulus spp. were absent. Sulfate reduction by one or more of these populations played a significant role in all digesters evaluated in this study. In addition, sulfate-reducing bacteria played a role in favoring methanogenesis by providing their substrates. The analysis of the two-phase digester indicated that true phase separation was not accomplished: significant levels of active methanogens were present in the first phase. It was determined that the dominant populations in the second phase were different from those in the single-phase digesters.
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