Bioaugmentation for Improved Recovery of Anaerobic Digesters After Toxicant Exposure

Bioaugmentation was investigated as a method to decrease the recovery period of anaerobic digesters exposed to a transient toxic event. Two sets of laboratory-scale digesters (SRT = 10 days, OLR = 2 g COD/L-day), started with inoculum from a digester stabilizing synthetic municipal wastewater solids (MW) and synthetic industrial wastewater (WW), respectively, were transiently exposed to the model toxicant, oxygen. Bioaugmented digesters received 1.2 g VSS/L-day of an H2-utilizing culture for which the archaeal community was analyzed. Soon after oxygen exposure, the bioaugmented digesters produced 25–60% more methane than non-bioaugmented controls (p \u3c 0.05). One set of digesters produced lingering high propionate concentrations, and bioaugmentation resulted in significantly shorter recovery periods. The second set of digesters did not display lingering propionate, and bioaugmented digesters recovered at the same time as non-bioaugmented controls. The difference in the effect of bioaugmentation on recovery may be due to differences between microbial communities of the digester inocula originally employed. In conclusion, bioaugmentation with an H2-utilizing culture is a potential tool to decrease the recovery period, decrease propionate concentration, and increase biogas production of some anaerobic digesters after a toxic event. Digesters already containing rapidly adaptable microbial communities may not benefit from bioaugmentation, whereas other digesters with poorly adaptable microbial communities may benefit greatly

Escherichia coli 30S ribosomal subunit assembly: a novel role for the DnaK chaperone system

The prokaryotic ribosome is a 2.5 MDa particle comprised of two asymmetric subunits, the large (50S) and small (30S) subunits. The large subunit contains two RNAs (5S and 23S) in addition to thirty-four proteins. The small subunit consists of one RNA (16S rRNA) and twenty-one proteins. Although the crystal structure has been solved, much remains to be revealed concerning the assembly of this macromolecular structure. Our laboratory is focused on the assembly of the small subunit. In vitro assembly of this structure was achieved in the late 1960\u27s and early 1970\u27s. At low temperature when 16S rRNA and all of the small subunit proteins are incubated together, only a subset of the proteins are able to associate with the RNA and a particle termed Reconstitution Intermediate (RI, 21S) results. When RI particles are heat treated, a conformational rearrangement occurs and RI* (26S) particles result that are capable of complete assembly with the remainder of the small subunit proteins, even at low temperature, to form functional 30S subunits. In vitro 30S subunit assembly requires long incubation periods, high ionic strength, and heat treatment. In light of these strict requirements, we hypothesized that assembly factors must exist in vivo to facilitate this crucial assembly process, making it accurate and efficient. We have identified the DnaK chaperone system as one such factor. The purified DnaK chaperone system is sufficient to facilitate in vitro 30S subunit assembly at low temperature, forming 30S particles that co-sediment, have the same protein complement, bind tRNA, and participate in polyphenylalanine synthesis like 30S subunits. Additionally, the association behavior of the DnaK chaperone system components with pre-30S particles in vitro was observed and found to be very similar to their association with substrate in their well-characterized protein folding role. Lastly, it was determined that DnaK binds small subunit components in vivo, including pre-processed 16S rRNA. This is the first evidence clearly demonstrating a direct link between the DnaK chaperone system and the assembly of ribosomes in E. coli, and the first instance in which an extra-ribosomal assembly factor has been shown to facilitate 30S subunit assembly in vitro

Methyl Coenzyme M Reductase (mcrA) Gene Abundance Correlates with Activity Measurements of Methanogenic H2/CO2-Enriched Anaerobic Biomass

Biologically produced methane (CH4) from anaerobic digesters is a renewable alternative to fossil fuels, but digester failure can be a serious problem. Monitoring the microbial community within the digester could provide valuable information about process stability because this technology is dependent upon the metabolic processes of microorganisms. A healthy methanogenic community is critical for digester function and CH4 production. Methanogens can be surveyed and monitored using genes and transcripts of mcrA, which encodes the α subunit of methyl coenzyme M reductase – the enzyme that catalyses the final step in methanogenesis. Using clone libraries and quantitative polymerase chain reaction, we compared the diversity and abundance of mcrA genes and transcripts in four different methanogenic hydrogen/CO2 enrichment cultures to function, as measured by specific methanogenic activity (SMA) assays using H2/CO2. The mcrA gene copy number significantly correlated with CH4 production rates using H2/CO2, while correlations between mcrA transcript number and SMA were not significant. The DNA and cDNA clone libraries from all enrichments were distinctive but community diversity also did not correlate with SMA. Although hydrogenotrophic methanogens dominated these enrichments, the results indicate that this methodology should be applicable to monitoring other methanogenic communities in anaerobic digesters. Ultimately, this could lead to the engineering of digester microbial communities to produce more CH4 for use as renewable fuel

Consistent use of proactive control and relation with academic achievement in childhood

As children become older, they better maintain task-relevant information in preparation of upcoming cognitive demands. This is referred to as proactive control, which is a key component of cognitive control development. However, it is still uncertain whether children engage in proactive control consistently across different contexts and how proactive control relates to academic abilities. This study used two common tasks—the AX Continuous Performance Task (AX-CPT) and the Cued Task-Switching Paradigm (CTS)—to examine whether proactive control engagement in 102 children (age range: 6.91–10.91 years) converges between the two tasks and predicts academic abilities. Proactive control indices modestly correlated between tasks in higher but not lower working-memory children, suggesting that consistency in proactive control engagement across contexts is relatively low during childhood but increases with working memory capacity. Further, working memory (but not verbal speed) predicted proactive control engagement in both tasks. While proactive control as measured by each task predicted math and reading performance, only proactive control measured by CTS additionally predicted reasoning, suggesting that proactive control can be used as a proxy for academic achievements

The morphogenetic role of midline mesendoderm and ectoderm in the development of the forebrain and the midbrain of the mouse embryo

The anterior midline tissue (AML) of the late gastrula mouse embryo comprises the axial mesendoderm and the ventral neuroectoderm of the prospective forebrain, midbrain and rostral hindbrain. In this study, we have investigated the morphogenetic role of defined segments of the AML by testing their inductive and patterning activity and by assessing the impact of their ablation on the patterning of the neural tube at the early-somite-stage. Both rostral and caudal segments of the AML were found to induce neural gene activity in the host tissue; however, the de novo gene activity did not show any regional characteristic that might be correlated with the segmental origin of the AML. Removal of the rostral AML that contains the prechordal plate resulted in a truncation of the head accompanied by the loss of several forebrain markers. However, the remaining tissues reconstituted Gsc and Shh activity and expressed the ventral forebrain marker Nkx2.1. Furthermore, analysis of Gsc-deficient embryos reveals that the morphogenetic function of the rostral AML requires Gsc activity. Removal of the caudal AML led to a complete loss of midline molecular markers anterior to the 4th somite. In addition, Nkx2.1 expression was not detected in the ventral neural tube. The maintenance and function of the rostral AML therefore require inductive signals emanating from the caudal AML. Our results point to a role for AML in the refinement of the anteroposterior patterning and morphogenesis of the brain

Limited genetic diversity in Salmonella enterica Serovar Enteritidis PT13

<p>Abstract</p> <p>Background</p> <p><it>Salmonella enterica </it>serovar Enteritidis has emerged as a significant foodborne pathogen throughout the world and is commonly characterized by phage typing. In Canada phage types (PT) 4, 8 and 13 predominate and in 2005 a large foodborne PT13 outbreak occurred in the province of Ontario. The ability to link strains during this outbreak was difficult due to the apparent clonality of PT13 isolates in Canada, as there was a single dominant pulsed-field gel electrophoresis (PFGE) profile amongst epidemiologically linked human and food isolates as well as concurrent sporadic strains. The aim of this study was to perform comparative genomic hybridization (CGH), DNA sequence-based typing (SBT) genomic analyses, plasmid analyses, and automated repetitive sequence-based PCR (rep-PCR) to identify epidemiologically significant traits capable of subtyping <it>S</it>. Enteritidis PT13.</p> <p>Results</p> <p>CGH using an oligonucleotide array based upon chromosomal coding sequences of <it>S. enterica </it>serovar Typhimurium strain LT2 and the <it>Salmonella </it>genomic island 1 successfully determined major genetic differences between <it>S</it>. Typhimurium and <it>S</it>. Enteritidis PT13, but no significant strain-to-strain differences were observed between <it>S</it>. Enteritidis PT13 isolates. Individual loci (<it>safA </it>and <it>fliC</it>) that were identified as potentially divergent in the CGH data set were sequenced in a panel of <it>S</it>. Enteritidis strains, and no differences were detected between the PT13 strains. Additional sequence-based typing was performed at the <it>fimA</it>, <it>mdh</it>, <it>manB</it>, <it>cyaA</it>, <it>citT</it>, <it>caiC</it>, <it>dmsA</it>, <it>ratA </it>and STM0660 loci. Similarly, no diversity was observed amongst PT13 strains. Variation in plasmid content between PT13 strains was observed, but macrorestriction with B<it>gl</it>II did not identify further differences. Automated rep-PCR patterns were variable between serovars, but <it>S</it>. Enteritidis PT13 strains could not be differentiated.</p> <p>Conclusion</p> <p>None of the methods identified any significant variation between PT13 strains. Greater than 11,300 base pairs of sequence for each of seven <it>S</it>. Enteritidis PT13 strains were analyzed without detecting a single polymorphic site, although diversity between different phage types of <it>S</it>. Enteritidis was observed. These data suggest that Canadian <it>S</it>. Enteritidis PT13 strains are highly related genetically.</p

Automatic Detection of Gaps in Availability of Authoritative Online Content

This disclosure describes techniques to measure authority content gap (ACG), which represents the (lack of) authoritativeness in online content related to individual topics. The ACG metric is defined for various verticals, e.g., health, government services, legal, etc., and can be specific to region, country, language, or time period. The ACG is refreshed periodically, and it can be used in combination with other metrics relating to a content publisher. The ACG is a useful measure in various contexts, e.g., when an unpopular or obscure topic achieves sudden popularity, or when a new topic emerges. The ACG for a topic can indicate when authoritative content about such topics is unavailable and can be utilized to ameliorate the situation, e.g., by alerting content providers about the content gap

The effect of metacognitive executive function training on children's executive function, proactive control, and academic skills

The current study investigated the effects of metacognitive and executive function (EF) training on childhood EF (inhibition, working memory [WM], cognitive flexibility, and proactive/reactive control) and academic skills (reading, reasoning, and math) among children from disadvantaged backgrounds. Children (N = 134, Mage = 8.70 years) were assigned randomly to the three training groups: (a) metacognitive training of basic EF processes (meta-EF), (b) training of basic EF processes (basic-EF), and (c) active controls (active control). They underwent 16 training sessions over the course of 2 months. No effects of EF and/or metacognitive training were found for academic outcomes. However, both meta-EF and basic-EF groups demonstrated greater gains than the active control group on proactive control engagement and WM, suggesting that EF training promotes a shift to more mature ways of engaging EF. Our findings suggest minimal near- and far-transfer effects of metacognitive training but highlight that proactive engagement of EF can be promoted through EF training in children

Ceftiofur Resistance in Salmonella enterica Serovar Heidelberg from Chicken Meat and Humans, Canada

Use of this drug in chickens may limit effectiveness of cephalosporins in treating human infections

Reply to the Comment on 'Quantum Phase Slips and Transport in Ultra-Thin Superconducting Wires'

We reply to the recent Comment [cond-mat/9702231] by J.-M. Duan. Our point of view is markedly different on every issue raised. Much of the disagreement can be traced to a different preception of experimentally relevant length scales. i) We explain the difference between our formulation, which rests on a microscopic basis, and the phenomenological one of the author. ii) Our renormalization scheme is fundamentally right, as the "log(log)" interaction appears only in wires of astronomical lengths. iii) The tunneling barrier is profoundly reduced by the kinetic inductance. iv) We do make an appropriate comparison to the data on the thinnest available wires.Comment: 1 page Revte