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Two 4-chloro-2-methylphenoxyacetic acid (MCPA)-degrading enrichment cultures selected from an aquifer on low (0.1 mg liter-1) or high (25 mg liter-1) MCPA concentrations were compared in terms of metabolic activity, community composition, population growth, and single cell physiology. Different community compositions and major shifts in community structure following exposure to different MCPA concentrations were observed using both 16S rRNA gene denaturing gradient gel electrophoresis fingerprinting and pyrosequencing. The communities also differed in their MCPA-mineralizing activities. The enrichments selected on low concentrations mineralized MCPA with shorter lag phases than those selected on high concentrations. Flow cytometry measurements revealed that mineralization led to cell growth. The presence of low-nucleic acid-content bacteria (LNA bacteria) was correlated with mineralization activity in cultures selected on low herbicide concentrations. This suggests that LNA bacteria may play a role in degradation of low herbicide concentrations in aquifers impacted by agriculture. This study shows that subpopulations of herbicide-degrading bacteria that are adapted to different pesticide concentrations can coexist in the same environment and that using a low herbicide concentration enables enrichment of apparently oligotrophic subpopulations. [ABSTRACT FROM AUTHOR]

Pellet softening reactors are used in centralized and decentralized drinking water treatment plants for the removal of calcium (hardness) through chemically induced precipitation of calcite. This is accomplished in fluidized pellet reactors, where a strong base is added to the influent to increase the pH and facilitate the process of precipitation on an added seeding material. Here we describe for the first time the opportunistic bacterial colonization of the calcite pellets in a full-scale pellet softening reactor and the functional contribution of these colonizing bacteria to the overall drinking water treatment process. ATP analysis, advanced microscopy, and community fingerprinting with denaturing gradient gel electrophoretic (DGGE) analysis were used to characterize the biomass on the pellets, while assimilable organic carbon (AOC), dissolved organic carbon, and flow cytometric analysis were used to characterize the impact of the biological processes on drinking water quality. The data revealed pellet colonization at concentrations in excess of 500 ng of ATP/g of pellet and reactor biomass concentrations as high as 220 mg of ATP/m3 of reactor, comprising a wide variety of different microorganisms. These organisms removed as much as 60% of AOC from the water during treatment, thus contributing toward the biological stabilization of the drinking water. Notably, only a small fraction (about 60,000 cells/ml) of the bacteria in the reactors was released into the effluent under normal conditions, while the majority of the bacteria colonizing the pellets were captured in the calcite structures of the pellets and were removed as a reusable product. [ABSTRACT FROM AUTHOR]

This study investigated the feasibility of a slow-release inoculation approach as a bioaugmentation strategy for the degradation of lindane (γ-hexachlorocyclohexane [γ-HCH]). Slow-release inoculation of Sphingomonas sp. γ 1-7 was established in both liquid and soil slurry microcosms using open-ended silicone tubes in which the bacteria are encapsulated in a protective nutrient-rich matrix. The capacity of the encapsulated cells to degrade lindane under aerobic conditions was evaluated in comparison with inoculation of free-living cells. Encapsulation of cells in tubes caused the removal of lindane by adsorption to the silicone tubes but also ensured prolonged biodegradation activity. Lindane degradation persisted 2.2 and 1.4 times longer for liquid and soil slurry microcosms, respectively, than that for inoculation with free cells. While inoculation of free-living cells led to a loss in lindane-degrading activity in limited time intervals, encapsulation in tubes allowed for a more stable actively degrading community. The loss in degrading activity was linked to the loss of the linA gene, encoding γ-HCH dehydrochlorinase (LinA), which is involved in the initial steps of the lindane degradation pathway. This work shows that a slow-release inoculation approach using a catabolic strain encapsulated in open-ended tubes is a promising bioaugmentation tool for contaminated sites, as it can enhance pollutant removal and can prolong the degrading activity in comparison with traditional inoculation strategies. [ABSTRACT FROM AUTHOR]

Microbial fuel cells hold great promise as a sustainable biotechnological solution to future energy needs. Current efforts to improve the efficiency of such fuel cells are limited by the lack of knowledge about the microbial ecology of these systems. The purposes of this study were (i) to elucidate whether a bacterial community, either suspended or attached to an electrode, can evolve in a microbial fuel cell to bring about higher power output, and (ii) to identify species responsible for the electricity generation. Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment of a biofuel cell in which glucose was used increased the output from an initial level of 0.6 W m-2 of electrode surface to a maximal level of 4.31 W m-2 (664 mV, 30.9 mA) when plain graphite electrodes were used. This result was obtained with an average loading rate of I g of glucose liter-1 day-1 and corresponded to 81% efficiency for electron transfer from glucose to electricity. Cyclic voltammetry indicated that the enhanced microbial consortium had either membrane-bound or excreted redox components that were not initially detected in the community. Dominant species of the enhanced culture were identified by denaturing gradient gel electrophoresis and culturing. The community consisted mainly of facultative anaerobic bacteria, such as Alcaligenes faecalis and Enterococcus gallinarum, which are capable of hydrogen production. Pseudomonas aeruginosa and other Pseudomonas species were also isolated. For several isolates, electrochemical activity was mainly due to excreted redox mediators, and one of these mediators, pyocyanin produced by P. aeruginosa, could be characterized. Overall, the enrichment procedure, irrespective of whether only attached or suspended bacteria were examined, selected for organisms capable of mediating the electron transfer either by direct bacterial transfer or by excretion of redox components. [ABSTRACT FROM AUTHOR]

During a study of ureolytic microbial calcium carbonate (CaCO[sub 3]) precipitation by bacterial isolates collected from different environmental samples, morphological differences were observed in the large CaCO[sub 3] crystal aggregates precipitated within bacterial colonies grown on agar. Based on these differences, 12 isolates were selected for further study. We hypothesized that the striking differences in crystal morphology were the result of different microbial species or, alternatively, differences in the functional attributes of the isolates selected. Sequencing of 16S rRNA genes showed that all of the isolates were phylogenetically closely related to the Bacillus sphaericus group. Urease gene diversity among the isolates was examined by using a novel application of PCR-denaturing gradient gel electrophoresis (DGGE). This approach revealed significant differences between the isolates. Moreover, for several isolates, multiple bands appeared on the DGGE gels, suggesting the apparent presence of different urease genes in these isolates. The substrate affinities (K[sub m]) and maximum hydrolysis rates (V[sub max]) of crude enzyme extracts differed considerably for the different strains. For certain isolates, the urease activity increased up to 10-fold in the presence of 30 mM calcium, and apparently this contributed to the characteristic crystal formation by these isolates. We show that strain-specific calcification occurred during ureolytic microbial carbonate precipitation. The specificity was mainly due to differences in urease expression and the response to calcium. [ABSTRACT FROM AUTHOR]

Evaluates the short-term effects of a 3-chloroaniline (CA) shock load and bioaugmentation with a 3-CA-degrading inoculant on reactor functions. Use of denaturing gradient gel electrophoresis, FISH and real-time PCR in examining the changes in the structure, abundance and activity of the nitrifying community; Sequences of the primers and probes used in the study.

Examines the diversity of the plasmids and of the gene tdnQ, involved in the oxidative deamination of aniline, in five bacterial strains that are able to metabolize both aniline and 3-chloroaniline (3-CA). Isolation and identification of 3-CA-metabolizing bacteria; Involvement of plasmids in aniline and 3-CA degradation; Comparison of partial tdnQ sequences.

Reports that a strain identified as Comamonas testosteroni I2 was isolated from activated sludge and found to be capable of mineralizing 3-chloroaniline (3-CA). Ability to clean wastewater containing 3-CA upon inoculation into activated sludge; Denaturing gradient gel electrophoresis; Nonpermanence of bioaugmentation.

Biofilms within drinking water distribution systems serve as a habitat for drinking water microorganisms. However, biofilms can negatively impact drinking water quality by causing water discoloration and deterioration and can be a reservoir for unwanted microorganisms. In this study, we investigated whether indicator organisms for drinking water quality, such as coliforms, can settle in mature drinking water biofilms. Therefore, a biofilm monitor consisting of glass rings was used to grow and sample drinking water biofilms. Two mature drinking water biofilms were characterized by flow cytometry, ATP measurements, confocal laser scanning microscopy, and 16S rRNA sequencing. Biofilms developed under treated chlorinated surface water supply exhibited lower cell densities in comparison with biofilms resulting from treated groundwater. Overall, the phenotypic as well as the genotypic characteristics were significantly different between both biofilms. In addition, the response of the biofilm microbiome and possible biofilm detachment after minor water quality changes were investigated. Limited changes in pH and free chlorine addition, to simulate operational changes that are relevant for practice, were evaluated. It was shown that both biofilms remained resilient. Finally, mature biofilms were prone to invasion of the coliform, Serratia fonticola. After spiking low concentrations (i.e., ±100 cells/100 mL) of the coliform to the corresponding bulk water samples, the coliforms were able to attach and get established within the mature biofilms. These outcomes emphasize the need for continued research on biofilm detachment and its implications for water contamination in distribution networks. [ABSTRACT FROM AUTHOR]

The development of viability quantitative PCR (v-qPCR) has allowed for a more accurate assessment of the viability of a microbial sample by limiting the amplification of DNA from dead cells. Although valuable, v-qPCR is not infallible. One of the most limiting factors for accurate live/dead distinction is the length of the qPCR amplicon used. However, no consensus or guidelines exist for selecting and designing amplicon lengths for optimal results. In this study, a wide range of incrementally increasing amplicon lengths (68 to 906 base pairs [bp]) was used on live and killed cells of nine bacterial species treated with a viability dye (propidium monoazide [PMA]). Increasing amplicon lengths up to approximately 200 bp resulted in increasing quantification cycle (Cq) differences between live and killed cells while maintaining a good qPCR efficiency. Longer amplicon lengths, up to approximately 400 bp, further increased the Cq difference but at the cost of qPCR efficiency. Above 400 bp, no valuable increase in Cq differences was observed. [ABSTRACT FROM AUTHOR]

Biofilms are complex polymicrobial communities which are often associated with human infections such as the oral disease periodontitis. Studying these complex communities under controlled conditions requires in vitro biofilm model systems that mimic the natural environment as close as possible. This study established a multispecies periodontal model in the drip flow biofilm reactor in order to mimic the continuous flow of nutrients at the air-liquid interface in the oral cavity. The design is engineered to enable real-time characterization. A community of five bacteria, Streptococcus gordonii-GFPmut3*, Streptococcus oralis-GFPmut3*, Streptococcus sanguinis-pVMCherry, Fusobacterium nucleatum, and Porphyromonas gingivalis-SNAP26 is visualized using two distinct fluorescent proteins and the SNAP-tag. The biofilm in the reactor develops into a heterogeneous, spatially uniform, dense, and metabolically active biofilm with relative cell abundances similar to those in a healthy individual. Metabolic activity, structural features, and bacterial composition of the biofilm remain stable from 3 to 6 days. As a proof of concept for our periodontal model, the 3 days developed biofilm is exposed to a prebiotic treatment with L-arginine. Multifaceted effects of L-arginine on the oral biofilm were validated by this model setup. L-arginine showed to inhibit growth and incorporation of the pathogenic species and to reduce biofilm thickness and volume. Additionally, L-arginine is metabolized by Streptococcus gordonii-GFPmut3* and Streptococcus sanguinis-pVMCherry, producing high levels of ornithine and ammonium in the biofilm. In conclusion, our drip flow reactor setup is promising in studying spatiotemporal behavior of a multispecies periodontal community. [ABSTRACT FROM AUTHOR]

Mesophilic (37°C) and thermophilic (52°C) anaerobic digestion of pig slurry induced at least a 4-log decrease in murine norovirus 1, used as a surrogate virus for porcine norovirus, after 13 and 7 days, respectively. Bacteroides fragilis phage B40-8, employed as a universal viral model, was lowered by 2.5 log after 7 days. The viral titer declined due to temperature and matrix effects. [ABSTRACT FROM AUTHOR]

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a carcinogenic heterocyclic aromatic amine formed in meat products during cooking. Although the formation of hazardous PhIP metabolites by mammalian enzymes has been extensively reported, research on the putative involvement of the human intestinal microbiota in PhIP metabolism remains scarce. In this study, the in vitro conversion of PhIP into its microbial derivate, 7-hydroxy-5-methyl-3-phenyl-6,7,8,9-tetrahydropyrido [3',2' :4,5] imidazo [1,2-a] pyrimidin-5-ium chloride (PhIP-Mi), by fecal samples from 18 human volunteers was investigated. High-performance liquid chromatography analysis showed that all human fecal samples transformed PhIP but with efficiencies ranging from 1.8 to 96% after 72 h of incubation. Two PhIP-transforming strains, PhIP-M1-a and PhIP-M1-b, were isolated from human feces and identified by fluorescent amplified fragment length polymorphism and plieS sequence analyses as Enterococcus faecium strains. Some strains from culture collections belonging to the species E. durans, E. aviuin, E.faecium, and Lactobacillus reuteri were also able to perform this transformation. Yeast extract, special peptone, and meat extract supported PhIP transformation by the enriched E. facciuni strains, while tryptone, monomeric sugars, starch, and cellulose did not. Glycerol was identified as a fecal matrix constituent required for PhIP transformation. Abiotic synthesis of PhIP-MI and quantification of the glycerol metabolite 3-hydroxypropionaldehyde (3-HPA) confirmed that the anaerobic fermentation of glycerol via 3-HPA is the critical bacterial transformation process responsible for the formation of PhIP-Mi. Whether it is a detoxification is still a matter of debate, since PhIP-Mi has been shown to be cytotoxic toward Caco-2 cells but is not mutagenic in the Ames assay. [ABSTRACT FROM AUTHOR]

There is an urgent need for sustainable protein supply routes with low environmental footprint. Recently, the use of hydrogen-oxidizing bacteria (HOB) as a platform for high-quality microbial protein (MP) production has regained interest. This study aims to investigate the added value of using conditions such as salt and temperature to steer HOB communities to lower diversities, while maintaining a high protein content and a high-quality amino acid profile. Pressure drop and hydrogen consumption were measured for 56 days to evaluate autotrophy of a total of six communities in serum flasks. Of the six communities, four were enriched under saline (0.0, 0.25, 0.5, and 1.0 mol NaCl liter−1) and two under thermophilic conditions (65°C). Five communities enriched for HOB were subsequently cultivated in continuously stirred reactors under the same conditions to evaluate their potential as microbial protein producers. The protein percentages ranged from 41 to 80%. The highest protein content was obtained for the thermophilic enrichments. Amino acid profiles were comparable to protein sources commonly used for feed purposes. Members of the genus Achromobacter were found to dominate the saline enrichments, while members of the genus Hydrogenibacillus were found to dominate the thermophilic enrichments. Here, we show that enriching for HOB while steering the community toward low diversity and maintaining a high-quality protein content can be successfully achieved, in both saline and thermophilic conditions. IMPORTANCE Alternative feed and food supply chains are required to decrease water and land use. HOB offer a promising substitute for traditional agricultural practice to produce microbial protein (MP) from residual materials and renewable energy. To safeguard product stability, the composition of the HOB community should be controlled. Defining strategies to maintain the stability of the communities is therefore key for optimization purposes. In this study, we use salt and temperature as independent conditions to stabilize the composition of the HOB communities. Based on the results presented, we conclude that HOB communities can be steered to have low diversity using the presented conditions while producing a desirable protein content with a valuable amino acid profile. [ABSTRACT FROM AUTHOR]

Clothing textiles protect our human body against external factors. These textiles are not sterile and can harbor high bacterial counts as sweat and bacteria are transmitted from the skin. We investigated the microbial growth and odor development in cotton and synthetic clothing fabrics. T-shirts were collected from 26 healthy individuals after an intensive bicycle spinning session and incubated for 28 h before analysis. A trained odor panel determined significant differences between polyester versus cotton fabrics for the hedonic value, the intensity, and five qualitative odor characteristics. The polyester T-shirts smelled significantly less pleasant and more intense, compared to the cotton T-shirts. A dissimilar bacterial growth was found in cotton versus synthetic clothing textiles. Micrococci were isolated in almost all synthetic shirts and were detected almost solely on synthetic shirts by means of denaturing gradient gel electrophoresis fingerprinting. A selective enrichment of micrococci in an in vitro growth experiment confirmed the presence of these species on polyester. Staphylococci were abundant on both cotton and synthetic fabrics. Corynebacteria were not enriched on any textile type. This research found that the composition of clothing fibers promotes differential growth of textile microbes and, as such, determines possible malodor generation. [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP) applied in the construction industry poses several disadvantages such as ammonia release to the air and nitric acid production. An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented here to overcome these disadvantages. To induce calcium carbonate precipitation, M. parvus was incubated at different calcium formate concentrations and starting culture densities. Up to 91.4% ± 1.6% of the initial calcium was precipitated in the methane-amended cultures compared to 35.1% ± 11.9% when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and subsequently calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A maximum 0.67 ± 0.03 g of CaCO3 g of Ca(CHOOH)2-1 calcium carbonate precipitate yield was obtained when a culture of 109 cells ml-1 and 5 g of calcium formate liter-1 were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, our approach presents significant improvements in the environmental sustainability of the application in the construction industry. [ABSTRACT FROM AUTHOR]

Termite-derived methane contributes 3 to 4%to the total methane budget globally. Termites are not known to harbor methaneoxidizing microorganisms (methanotrophs). However, a considerable fraction of the methane produced can be consumed by methanotrophs that inhabit the mound material, yet the methanotroph ecology in these environments is virtually unknown. The potential for methane oxidation was determined using slurry incubations under conditions with high (12%) and in situ (∼0.004%) methane concentrations through a vertical profile of a termite (Macrotermes falciger) mound and a reference soil. Interestingly, the mound material showed higher methanotrophic activity. The methanotroph community structure was determined by means of a pmoA-based diagnostic microarray. Although the methanotrophs in the mound were derived from populations in the reference soil, it appears that termite activity selected for a distinct community. Applying an indicator species analysis revealed that putative atmospheric methane oxidizers (high-indicator-value probes specific for the JR3 cluster) were indicative of the active nest area, whereas methanotrophs belonging to both type I and type II were indicative of the reference soil. We conclude that termites modify their environment, resulting in higher methane oxidation and selecting and/or enriching for a distinct methanotroph population. [ABSTRACT FROM AUTHOR]

The methanotrophic potential in sewage treatment sludge was investigated. We detected a diverse aerobic methanotrophic community that potentially plays a significant role in mitigating methane emission in this environment. The results suggest that community structure was determined by conditions specific to the processes in a sewage treatment plant. [ABSTRACT FROM AUTHOR]

To study the gastrointestinal survival and enterotoxin production of the food-borne pathogen Bacillus cereus, an in vitro simulation experiment was developed to mimic gastrointestinal passage in 5 phases: (i) the mouth, (ii) the stomach, with gradual pH decrease and fractional emptying, (iii) the duodenum, with high concentrations of bile and digestive enzymes, (iv) dialysis to ensure bile reabsorption, and (v) the ileum, with competing human intestinal bacteria. Four different B. cereus strains were cultivated and sporulated in mashed potato medium to obtain an inoculum of 7.0 log spores/ml. The spores showed survival and germination during the in vitro simulation of gastrointestinal passage, but vegetative outgrowth of the spores was suppressed by the intestinal bacteria during the final ileum phase. No bacterial proliferation or enterotoxin production was observed, despite the high inoculum levels. Little strain variability was observed: except for the psychrotrophic food isolate, the spores of all strains survived well throughout the gastrointestinal passage. The in vitro simulation experiments investigated the survival and enterotoxin production of B. cereus in the gastrointestinal lumen. The results obtained support the hypothesis that localized interaction of B. cereus with the host's epithelium is required for diarrheal food poisoning. [ABSTRACT FROM AUTHOR]

Chloropropham-degrading cultures were obtained from sludge and soil samples by using two different enrichment techniques: (i) planktonic enrichments in shaken liquid medium and (ii) biofilm enrichments on two types of solid matrixes (plastic chips and gravel). Denaturing gradient gel electrophoresis fingerprinting showed that planktonic and biofilm cultures had a different community composition depending on the presence and type of added solid matrix during enrichment. This was reflected in the unique chloropropham-degrading species that could be isolated from the different cultures. Planktonic and biofilm cultures also differed in chloropropham-degrading activity. With biofilm cultures, slower chloropropham removal was observed, but with less build-up of the toxic intermediate 3-chloroaniline. Disruption of the biofilm architecture resulted in degradation characteristics shifting toward those of the free suspensions, indicating the importance of a well-established biofilm structure for good performance. These results show that biofilm-mediated enrichment techniques can be used to select for pollutant-degrading microorganisms that like to proliferate in a biofilm and that cannot be isolated using conventional shaken-liquid procedures. Furthermore, the influence of the biofilm architecture on the pesticide degradation characteristics suggests that for bioaugmentation the use of biofilm catabolic communities might be a proficient alternative to using planktonic freely suspended cultures. [ABSTRACT FROM AUTHOR]

By placing the anode of a sediment microbial fuel cell (SMFC) in the rhizosphere of a rice plant, rootexcreted rhizodeposits can be microbially oxidized with concomitant current generation. Here, various molecular techniques were used to characterize the composition of bacterial and archaeal communities on such anodes, as influenced by electrical circuitry, sediment matrix, and the presence of plants. Closed-circuit anodes in potting soil were enriched with Desulfobulbus-like species, members of the family Geobacteraceae, and as yet uncultured representatives of the domain Archaea. [ABSTRACT FROM AUTHOR]

The presence of enteric viruses in drinking water is a potential health risk. Growing interest has arisen in nanometals for water disinfection, in particular the use of silver-based nanotechnology. In this study, Lactobacillus fermentum served as a reducing agent and bacterial carrier matrix for zerovalent silver nanoparticles, referred to as biogenic Ag°. The antiviral action of biogenic Ag° was examined in water spiked with an Enterobacter aerogenes-infectiiig bacteriophage (UZ1). Addition of 5.4 mg liter-1 biogenic Ag° caused a 4.0-log decrease of the phage after 1 h, whereas the use of chemically produced silver nanoparticles (nAg°) showed no inactivation within the same time frame. A control experiment with 5.4 mg liter-1 ionic Ag+ resulted in a similar inactivation after 5 h only. The antiviral properties of biogenic Ag° were also demonstrated on the murine norovirus 1 (MNV-1), a model organism for human noroviruses. Biogenic Ag° was applied to an electropositive cartridge filter (NanoCeram) to evaluate its capacity for continuous disinfection. Addition of 31.25 mg biogenic Ag° m-2 on the filter (135 mg biogenic Ag° kg-1 filter medium) caused a 3.8-log decline of the virus. In contrast, only a 1.5-log decrease could be obtained with the original filter. This is the first report to demonstrate the antiviral efficacy of extracellular biogenic Ag° and its promising opportunities for continuous water disinfection. [ABSTRACT FROM AUTHOR]

Aerobic ammonium-oxidizing bacteria (AerAOB) and anoxic ammonium-oxidizing bacteria (AnAOB) cooperate in partial nitritation/anammox systems to remove ammonium from wastewater. In this process, large granular microbial aggregates enhance the performance, but little is known about granulation so far. In this study, three suspended-growth oxygen-limited autotrophic nitrification-denitrification (OLAND) reactors with different inoculation and operation (mixing and aeration) conditions, designated reactors A, B, and C, were used. The test objectives were (i) to quantify the AerAOB and AnAOB abundance and the activity balance for the different aggregate sizes and (ii) to relate aggregate morphology, size distribution, and architecture putatively to the inoculation and operation of the three reactors. A nitrite accumulation rate ratio (NARR) was defined as the net aerobic nitrite production rate divided by the anoxic nitrite consumption rate. The smallest reactor A, B, and C aggregates were nitrite sources (NARR, >1.7). Large reactor A and C aggregates were granules capable of autonomous nitrogen removal (NARR, 0.6 to 1.1) with internal AnAOB zones surrounded by an AerAOB rim. Around 50% of the autotrophic space in these granules consisted of AerAOB- and AnAOB-specific extracellular polymeric substances. Large reactor B aggregates were thin film-like nitrite sinks (NARR, <0.5) in which AnAOB were not shielded by an AerAOB layer. Voids and channels occupied 13 to 17% of the anoxic zone of AnAOB-rich aggregates (reactors B and C). The hypothesized granulation pathways include granule replication by division and budding and are driven by growth and/or decay based on species. specific physiology and by hydrodynamic shear and mixing. [ABSTRACT FROM AUTHOR]

Optimization of the fatty acid composition of ruminant milk and meat is desirable. Dietary supplementation of algae was previously shown to inhibit rumen biohydrogenation, resulting in an altered milk fatty acid profile. Bacteria involved in biohydrogenation belong to the Butyrivibrio group. This study was aimed at relating accumulation of biohydrogenation intermediates with shifts in Butyrivibrio spp. in the rumen of dairy cows. Therefore, an experiment was performed with three rumen-fistulated dairy cows receiving a concentrate containing algae (9.35 g/kg total dry matter [DM] intake) for 20 days. Supplementation of the diet with algae inhibited biohydrogenation of C18:2 omega 6 (n-6) and C18:1 n-3, resulting in increased concentrations of biohydrogenation intermediates, whereas C18:0 decreased. Addition of algae increased ruminal C18:1 trans fatty acid concentrations, mainly due to 6- and 20-fold increases in C18:1 trans 11 (t11) and C18:1 t10. The number of ciliates (5.37 log copies/g rumen digesta) and the composition of the ciliate community were unaffected by dietary algae. In contrast, supplementation of the diet with algae changed the composition of the bacterial community. Primers for the Butyrivibrio group, including the genera Butyrivibrio and Pseudobutyrivibrio, were specifically designed. Denaturing gradient gel electrophoresis showed community changes upon addition of algae without affecting the total amount of Butyrivibrio bacteria (7.06 log copies/g rumen DM). Clone libraries showed that algae affected noncultivated species, which cluster taxonomically between the genera Butyrivibrio and Pseudobutyrivibrio and might play a role in biohydrogenation. In addition, 20% of the clones from a randomly selected rumen sample were related to the C18:0-producing branch, although the associated C18:0 concentration decreased through supplementation of the diet with algae. [ABSTRACT FROM AUTHOR]

A sequential batch reactor (SBR) and a membrane bioreactor (MBR) were inoculated with the same sludge from a municipal wastewater treatment plant, supplemented with ammonium, and operated in parallel for 84 days. It was investigated whether the functional stability of the nitrification process corresponded with a static ammonia-oxidizing bacterial (AOB) community. The SBR provided complete nitrification during nearly the whole experimental run, whereas the MBR showed a buildup of 0 to 2 mg nitrite-N liter-1 from day 45 until day 84. Based on the denaturing gradient gel electrophoresis profiles, two novel approaches were introduced to characterize and quantify the community dynamics and interspecies abundance ratios: (i) the rate of change [Δt(week)] parameter and (ii) the Pareto-Lorenz curve distribution pattern. During the whole sampling period, it was observed that neither of the reactor types maintained a static microbial community and that the SBR evolved more gradually than the MBR, particularly with respect to AOB (i.e., average weekly community changes of 12.6% ± 5.2% for the SBR and 24.6% ± 143% for the MBR). Based on the Pareto-Lorenz curves, it was observed that only a small group of AOB species played a numerically dominant role in the nitritation of both reactors, and this was true especially for the MBR. The remaining less dominant species were speculated to constitute a reserve of AOB which can proliferate to replace the dominant species. The value of these parameters in terms of tools to assist the operation of activated-sludge systems is discussed. [ABSTRACT FROM AUTHOR]

A mixed culture dechlorinating 1,2-dichloroethane (1,2-DCA) to ethene was enriched from groundwater that had been subjected to long-term contamination. In the metagenome of the enrichment, a 7-kb reductive dehalogenase (RD) gene cluster sequence was detected by inverse and direct PCR. The RD gene cluster had four open reading frames (ORF) showing 99% nucleotide identity with pceB, pceC, pceT, and orf1 of Dehalobacter restrictus strain DSMZ 9455T, a bacterium able to dechlorinate chlorinated ethenes. However, dcaA, the ORF encoding the catalytic subunit, showed only 94% nucleotide and 90% amino acid identity with pceA of strain DSMZ 9455T. Fifty-three percent of the amino acid differences were localized in two defined regions of the predicted protein. Exposure of the culture to 1,2-DCA and lactate increased the dcaA gene copy number by 2 log units, and under these conditions the dcaA and dcaB genes were actively transcribed. A very similar RI) gene cluster with 98% identity in the dcaA gene sequence was identified in Desulfilobacterium dichioroeliminans strain DCA1, the only known isolate that selectively dechlorinates 1,2-DCA but not chlorinated ethenes. The dcaA gene of strain DCA1 possesses the same amino acid motifs as the new dcaA gene. Southern hybridization using total genomic DNA of strain DCA1 with dcaA gene-specific and dcaB- and pceB-targeting probes indicated the presence of two identical or highly similar dehalogenase gene clusters. In conclusion, these data suggest that the newly described RDs are specifically adapted to 1,2-DCA dechlorination. [ABSTRACT FROM AUTHOR]

An evolutionary algorithm was applied to study the complex interactions between medium parameters and their effects on the isolation of denitrifying bacteria, both in number and in diversity. Growth media with a pH of 7 and a nitrogen concentration of 3 mM, supplemented with 1 ml of vitamin solution but not with sodium chloride or riboflavin, were the most successful for the isolation of denitrifiers from activated sludge. The use of ethanol or succinate as a carbon source and a molar C/N ratio of 2.5, 20, or 25 were also favorable. After testing of 60 different medium parameter combinations and comparison with each other as well as with the standard medium Trypticase soy agar supplemented with nitrate, three growth media were highly suitable for the cultivation of denitrifying bacteria. All evaluated isolation conditions were used to study the cultivable denitrifier diversity of activated sludge from a municipal wastewater treatment plant. One hundred ninety-nine denitrifiers were isolated, the majority of which belonged to the Betaproteobacteria (50.4%) and the Alphaproteobacteria (36.8%). Representatives of Gammaproteobacteria (5.6%), Epsilonproteobacteria (2%), and Firmicutes (4%) and one isolate of the Bacteroidetes were also found. This study revealed a much more diverse denitrifying community than that previously described in cultivation-dependent research on activated sludge. [ABSTRACT FROM AUTHOR]

Determines the bacterial community composition of a linuron-degrading enrichment culture. Role of the individual strains found in the culture in linuron degradation; Use of denaturing gradient gel electrophoresis, isolation and identification of strains and biodegradation assays; Advantage of variovorax sp. strain WDL1 over WDL1 alone in accelerating the degradation of linuron.