Distribution and Rate of Microbial Processes in an Ammonia-Loaded Air Filter Biofilm

The in situ activity and distribution of heterotrophic and nitrifying bacteria and their potential interactions were investigated in a full-scale, two-section, trickling filter designed for biological degradation of volatile organics and NH₃ in ventilation air from pig farms. The filter biofilm was investigated by microsensor analysis, fluorescence in situ hybridization, quantitative PCR, and batch incubation activity measurements. In situ aerobic activity showed a significant decrease through the filter, while the distribution of ammonia-oxidizing bacteria (AOB) was highly skewed toward the filter outlet. Nitrite oxidation was not detected during most of the experimental period, and the AOB activity therefore resulted in NO₂⁻, accumulation, with concentrations often exceeding 100 mM at the filter inlet. The restriction of AOB to the outlet section of the filter was explained by both competition with heterotrophic bacteria for O₂ and inhibition by the protonated form of NO₂⁻, HNO₂. Product inhibition of AOB growth could explain why this type of filter tends to emit air with a rather constant NH₃ concentration irrespective of variations in inlet concentration and airflow.Emissions of NH₃, odorous organic gasses, and dust from pig facilities cause significant problems for neighbors and the surrounding natural environment. In Denmark, swine production accounts for 34% of the total atmospheric NH₃ emission, of which 50% originates from pig house emissions (19). Furthermore, multiple volatile and very odorous organic compounds are emitted with animal house exhaust air and constitute a severe nuisance in residential areas (16, 31). While biofilters based on wood chips, compost, and peat have proven efficient in removing complex mixtures of volatile organic compounds (VOC) from piggery exhaust air, biotrickling filters have been shown to be efficient in both odor and NH₃ removal (30). In these filters, airborne VOC and NH₃ are taken up by an irrigated biofilm and oxidized by organoheterotrophic and nitrifying bacteria, respectively, resulting in the production of CO₂, NO₂⁻ or NO₃⁻, and microbial biomass (43). The nitrification process, which comprises the two-step oxidation of NH₃ via NO₂⁻ to NO₃⁻, is catalyzed by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea and by nitrite-oxidizing bacteria (NOB), respectively (22, 23). However, in many biotrickling filters, NOB activity seems to be absent, resulting in NO₂⁻ being the end product of nitrification (29).Waste products often accumulate in biotrickling filters, as the water is recycled many times to minimize wastewater discharge. In particular, NO₂⁻ may accumulate to concentrations above 100 mM (29), resulting in high levels of free nitrous acid (FNA, or HNO₂), which is inhibitory to many microorganisms (2, 40, 50). As a result of an overall countercurrent air-water flow, FNA, VOC, and NH₃ concentrations are expected to decrease from the filter air inlet toward the outlet, potentially promoting a gradient of microbial processes and species distribution through the filter.Also, on a smaller scale, physical and chemical heterogeneity results in microgradients of substrates and O₂ within the biofilm that may affect the spatial distribution and rate of microbial processes. While considerable research effort has been given to the physicochemical aspects of filter optimization (11, 44), very little is known about the distribution, activity, and potential interactions of bacterial processes in the biofilm. Problems frequently arise, such as highly variable odor reduction, failed NH₃ removal, and filter clogging due to excess biofilm growth and slime excretion. Improved insight into the dynamics of the microbial activities may help control the biological processes in order to optimize and stabilize filter performance.In this study, the in situ activity and distribution of organoheterotrophic bacteria and AOB and the identity and NH₃ oxidation potential of the AOB were investigated in a two-section, full-scale biological air filter treating waste gas from a pig facility. Biofilms in different filter sections along a gradient of decreasing VOC and NH₃ load and NO₂⁻ accumulation were characterized. The goal was to attain a basic understanding of the microbial processes and thus filter function.     

Mechanisms of haplotype divergence at the <Emphasis Type="Italic">RGA08</Emphasis> nucleotide-binding leucine-rich repeat gene locus in wild banana <Emphasis Type="Italic">(Musa balbisiana)</Emphasis>

Background  

Comparative sequence analysis of complex loci such as resistance gene analog clusters allows estimating the degree of sequence conservation and mechanisms of divergence at the intraspecies level. In banana (Musa sp.), two diploid wild species Musa acuminata (A genome) and Musa balbisiana (B genome) contribute to the polyploid genome of many cultivars. The M. balbisiana species is associated with vigour and tolerance to pests and disease and little is known on the genome structure and haplotype diversity within this species. Here, we compare two genomic sequences of 253 and 223 kb corresponding to two haplotypes of the RGA08 resistance gene analog locus in M. balbisiana "Pisang Klutuk Wulung" (PKW).     

Inherent trait differences explain wheat cultivar responses to climate factor interactions: New insights for more robust crop modelling

Climate change predictions foresee a combination of rising CO₂, temperature and altered precipitation. Effects of single climatic variables are well defined, but the importance of combined variables and genotypic effects is less known, although pivotal for assessing climate change impacts, for example, with crop growth models. This study provides developmental and physiological data from combined climatic factors for two distinct wheat cultivars (Paragon and Gladius), as a basis to improve predictions for climate change scenarios. The two cultivars were grown in controlled climate chambers in a fully factorial setup of atmospheric CO₂ concentration, growth temperature and watering regime. The cultivars differed considerably in their developmental rate, response pattern and the parameters responsible for most of their variation. The growth of Paragon was linked to climatic effects on photosynthesis and mainly affected by temperature. Paragon was overall more negatively affected by all treatment combinations compared to Gladius. Gladius was mostly affected by watering regime. The cultivars' acclimation strategies to climate factors varied significantly. Thus, considering a single factor is an oversimplification very likely impacting the accuracy of crop growth models. Intraspecific crop variation could help understanding genotype by environment variation. Cultivars with high phenotypic plasticity may have greater resilience against climatic variability.     

Foliar abscisic acid content underlies genotypic variation in stomatal responsiveness after growth at high relative air humidity

Background and Aims

Stomata formed at high relative air humidity (RH) respond less to abscisic acid (ABA), an effect that varies widely between cultivars. This study tested the hypotheses that this genotypic variation in stomatal responsiveness originates from differential impairment in intermediates of the ABA signalling pathway during closure and differences in leaf ABA concentration during growth.

Methods

Stomatal anatomical features and stomatal responsiveness to desiccation, feeding with ABA, three transduction elements of its signalling pathway (H₂O₂, NO, Ca²⁺) and elicitors of these elements were determined in four rose cultivars grown at moderate (60 %) and high (90 %) RH. Leaf ABA concentration was assessed throughout the photoperiod and following mild desiccation (10 % leaf weight loss).

Key Results

Stomatal responsiveness to desiccation and ABA feeding was little affected by high RH in two cultivars, whereas it was considerably attenuated in two other cultivars (thus termed sensitive). Leaf ABA concentration was lower in plants grown at high RH, an effect that was more pronounced in the sensitive cultivars. Mild desiccation triggered an increase in leaf ABA concentration and equalized differences between leaves grown at moderate and high RH. High RH impaired stomatal responses to all transduction elements, but cultivar differences were not observed.

Conclusions

High RH resulted in decreased leaf ABA concentration during growth as a result of lack of water deficit, since desiccation induced ABA accumulation. Sensitive cultivars underwent a larger decrease in leaf ABA concentration rather than having a higher ABA concentration threshold for inducing stomatal functioning. However, cultivar differences in stomatal closure following ABA feeding were not apparent in response to H₂O₂ and downstream elements, indicating that signalling events prior to H₂O₂ generation are involved in the observed genotypic variation.     

The bestrophin- and TMEM16A-associated Ca2+-activated Cl– channels in vascular smooth muscles

The presence of Ca²⁺-activated Cl^– currents (I_Cl(Ca)) in vascular smooth muscle cells (VSMCs) is well established. I_Cl(Ca) are supposedly important for arterial contraction by linking changes in [Ca²⁺]_i and membrane depolarization. Bestrophins and some members of the TMEM16 protein family were recently associated with I_Cl(Ca). Two distinct I_Cl(Ca) are characterized in VSMCs; the cGMP-dependent I_Cl(Ca) dependent upon bestrophin expression and the ‘classical’ Ca²⁺-activated Cl^– current, which is bestrophin-independent. Interestingly, TMEM16A is essential for both the cGMP-dependent and the classical I_Cl(Ca). Furthermore, TMEM16A has a role in arterial contraction while bestrophins do not. TMEM16A’s role in the contractile response cannot be explained however only by a simple suppression of the depolarization by Cl^– channels. It is suggested that TMEM16A expression modulates voltage-gated Ca²⁺ influx in a voltage-independent manner and recent studies also demonstrate a complex role of TMEM16A in modulating other membrane proteins.     

DNA methylation changes associated with risk factors in tumors of the upper aerodigestive tract

Cancers of the upper aerodigestive tract (UADT) are common forms of malignancy associated with tobacco and alcohol exposures, although human papillomavirus and nutritional deficiency are also important risk factors. While somatically acquired DNA methylation changes have been associated with UADT cancers, what triggers these events and precise epigenetic targets are poorly understood. In this study, we applied quantitative profiling of DNA methylation states in a panel of cancer-associated genes to a case-control study of UADT cancers. Our analyses revealed a high frequency of aberrant hypermethylation of several genes, including MYOD1, CHRNA3 and MTHFR in UADT tumors, whereas CDKN2A was moderately hypermethylated. Among differentially methylated genes, we identified a new gene (the nicotinic acetycholine receptor gene) as target of aberrant hypermethylation in UADT cancers, suggesting that epigenetic deregulation of nicotinic acetycholine receptors in non-neuronal tissues may promote the development of UADT cancers. Importantly, we found that sex and age is strongly associated with the methylation states, whereas tobacco smoking and alcohol intake may also influence the methylation levels in specific genes. This study identifies aberrant DNA methylation patterns in UADT cancers and suggests a potential mechanism by which environmental factors may deregulate key cellular genes involved in tumor suppression and contribute to UADT cancers.Key words: DNA methylation, upper aerodigestive tract, cancer, risk factors, biomarkers     

Effects of intravenous infusion of prostacyclin (PGI2) in man

Prostacyclin infused intravenously in human volunteers induces ex vivo inhibition of platelet aggregation, tachycardia and hypotension. The inhibition of platelet aggregation is obtained with slightly lower doses than those which exhibit cardiovascular effects.The cardiovascular effects disappeared within a few minutes after discontinuing the infusion of prostacyclin but the platelet effects were longer lasting.Prostacyclin did not have any effect on platelet count, platelet factor 3, accelerated partial thromboplastin time, prothrombin time, euglobulin clot lysis time, fibrinogen degradation products, blood glucose concentration or urine sodium potassium ratio.