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Dominant Bacteria (dominant + bacteria)
Selected AbstractsMolecular analysis of ammonia-oxidizing bacteria community in intermittent aeration sequencing batch reactors used for animal wastewater treatmentENVIRONMENTAL MICROBIOLOGY, Issue 11 2006Kenichi Otawa Summary Bacterial communities and betaproteobacterial ammonia-oxidizing bacteria (AOB) communities were evaluated seasonally in an intermittent-aeration sequencing batch process (SBR, plant A) and in 12 other livestock wastewater treatment plants (WWTP): eight SBRs and four conventional activated-sludge systems. Microbial communities were analysed by reverse transcription polymerase chain reaction followed by denaturing-gradient gel electrophoresis (DGGE) and the construction of clone libraries for 16S rRNA and ammonia monooxygenase (amoA) genes. In plant A, the dominant bacteria were as-yet-uncultured bacteria of Bacteroidetes and Proteobacteria, and the DGGE profiles showed that the bacterial communities were stable during a given treatment cycle, but changed seasonally. In betaproteobacterial AOB communities, two AOB phylotypes (members of the Nitrosomonas ureae,oligotropha,marina cluster) were dominant during the seasons in plant A. Although the dominant AOB phylotypes differed among the 13 WWTPs, dominance by one or two AOB phylotypes was commonly observed in all plants. Sequencing of the DGGE bands indicated that amoA sequences belonging to the Nitrosomonas europaea,eutropha cluster were dominant in 11 plants, where the ammonia-nitrogen concentration was high in the raw wastewater, whereas those belonging to the Nitrosomonas ureae,oligotropha,marina cluster were dominant in two plants where the concentration was relatively low. Even though we detected many minor amoA sequences by means of five clone libraries for the A to D plants, no libraries comprised both amoA sequences belonging to the two clusters, indicating that the dominant AOBs were defined by cluster level in each plant. [source] Microbiological, chemical and sensory changes of whole and filleted Mediterranean aquacultured sea bass (Dicentrarchus labrax) stored in iceJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2003Dimitra Taliadourou Abstract The effect of filleting on the microbiological, chemical and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads, H2S-producing bacteria (including Shewanella putrefaciens) and Brochothrix thermosphacta were the dominant bacteria at the end of the 16 day storage period in ice for both whole ungutted and filleted sea bass. Enterobacteriaceae were also found in the spoilage microflora of whole ungutted and filleted sea bass, but their counts were always lower than those of pseudomonads, H2S-producing bacteria (including S putrefaciens) and B thermosphacta. Total viable counts for whole ungutted sea bass were always lower than those for filleted sea bass samples. Of the chemical indicators of spoilage, TMA (trimethylamine) values of whole ungutted sea bass increased very slowly, whereas significantly higher values were obtained for filleted samples, with respective values of 0.253 and 1.515 mg N per 100 g muscle being reached at the end of their shelf-life (days 13 and 9 respectively). TVB-N (total volatile basic nitrogen) values showed a slight increase for whole ungutted sea bass during storage, reaching a value of 26.77 mg N per 100 g muscle (day 13), whereas for filleted fish a corresponding value of 26.88 mg N per 100 g muscle was recorded (day 9). TBA (thiobarbituric acid) values increased slowly for whole ungutted and filleted sea bass samples throughout the entire storage period, reaching final values of 4.48 (day 13) and 13.84 (day 9) mg malonaldehyde kg,1 respectively. Sensory assessment of raw fish using the EC freshness scale gave a grade E for up to 5 days for whole ungutted sea bass, a grade A for a further 4 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Overall acceptability scores for odour, taste and texture of cooked whole ungutted and filleted sea bass decreased with increasing time of storage. The results of this study indicate that the shelf-life of sea bass stored in ice, as determined by overall acceptability sensory scores and microbiological data, is 8,9 days for filleted and 12,13 days for whole ungutted fish. Copyright © 2003 Society of Chemical Industry [source] Characterization of electrochemical activity of a strain ISO2-3 phylogenetically related to Aeromonas sp. isolated from a glucose-fed microbial fuel cellBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Kyungmi Chung Abstract The microbial communities associated with electrodes in closed and open circuit microbial fuel cells (MFCs) fed with glucose were analyzed by 16S rRNA approach and compared. The comparison revealed that bacteria affiliated with the Aeromonas sp. within the Gammaproteobacteria constituted the major population in the closed circuit MFC (harvesting electricity) and considered to play important roles in current generation. We, therefore, attempted to isolate the dominant bacteria from the anode biofilm, successfully isolated a Fe (III)-reducing bacterium phylogenetically related to Aeromonas sp. and designated as strain ISO2-3. The isolated strain ISO2-3 could grow and concomitantly produce current (max. 0.24,A/m2) via oxidation of glucose or hydrogen with an electrode serving as the sole electron acceptor. The strain could ferment glucose, but generate less electrical current. Cyclic voltammetry supported the strain ISO2-3 was electrically active and likely to transfer electrons to the electrode though membrane-associated compounds (most likely c-type cytochrome). This mechanism requires intimate contact with the anode surface. Scanning electron microscopy revealed that the strain ISO2-3 developed multiplayer biofilms on the anode surface and also produced anchor-like filamentous appendages (most likely pili) that may promote long-range electron transport across the thick biofilm. Biotechnol. Bioeng. 2009; 104: 901,910. © 2009 Wiley Periodicals, Inc. [source] Microbiological and geochemical dynamics in simulated-heap leaching of a polymetallic sulfide oreBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2008Kathryn Wakeman Abstract The evolution of microbial populations involved in simulated-heap leaching of a polymetallic black schist sulfide ore (from the recently-commissioned Talvivaara mine, Finland) was monitored in aerated packed bed column reactors over a period of 40 weeks. The influence of ore particle size (2-6.5 mm and 6.5-12 mm) on changes in composition of the bioleaching microflora and mineral leaching dynamics in columns was investigated and compared to fine-grain (<2 µm) ore that was bioprocessed in shake flask cultures. Both column reactors and shake flasks were inoculated with 24 different species and strains of mineral-oxidizing and other acidophilic micro-organisms, and maintained at 37°C. Mineral oxidation was most rapid in shake flask cultures, with about 80% of both manganese and nickel and 68% of zinc being leached within 6 weeks, though relatively little of the copper present in the ore was solubilised. The microbial consortium that emerged from the original inoculum was relatively simple in shake flasks, and was dominated by the iron-oxidizing autotroph Leptospirillum ferriphilum, with smaller numbers of Acidimicrobium ferrooxidans, Acidithiobacillus caldus and Leptospirillum ferrooxidans. Both metal recovery and (for the most part) total numbers of prokaryotes were greater in the column reactor containing the medium-grain than that containing the coarse-grain ore. The bioleaching communities in the columns displayed temporal changes in composition and differed radically from those in shake flask cultures. While iron-oxidizing chemoautotrophic bacteria were always the most numerically dominant bacteria in the medium-grain column bioreactor, there were major shifts in the most abundant species present, with the type strain of Acidithiobacillus ferrooxidans dominating in the early phase of the experiment and other bacteria (At. ferrooxidans NO37 and L. ferriphilum) dominating from week 4 to week 40. With the coarse-grain column bioreactor, similar transitions in populations of iron-oxidizing chemoautotrophs were observed, though heterotrophic acidophiles were often the most abundant bacteria found in mineral leach liquors. Four bacteria not included in the mixed culture used to inoculate the columns were detected by biomolecular techniques and three of these (all Alicyclobacillus -like Firmicutes) were isolated as pure cultures. The fourth bacterium, identified from a clone library, was related to the Gram-positive sulfate reducer Desulfotomaculum salinum. All four were considered to have been present as endospores on the dried ore, which was not sterilized in the column bioreactors. Two of the Alicyclobacillus -like isolates were found, transiently, in large numbers in mineral leachates. The data support the hypothesis that temporal and spatial heterogeneity in mineral heaps create conditions that favour different mineral-oxidizing microflora, and that it is therefore important that sufficient microbial diversity is present in heaps to optimize metal extraction. Biotechnol. Bioeng. 2008;101: 739,750. © 2008 Wiley Periodicals, Inc. [source] | ||||||||||