A bet-hedging strategy for denitrifying bacteria curtails their release of N2O

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Nitrous oxide respiring bacteria in biogas digestates for reduced agricultural emissions

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Nyoppdagede aspekter rundt denitrifiserende bakteriers økofysiologi, og deres rolle i N2O emisjoner

Environmental bacteria are in general limited by nutrient availability, and as the conditions fluctuate rapidly and unpredictably they must adapt or they will not thrive. This requires fast and adequate sensing and responding mechanisms, assuring fitness with minimum investment, as there is not much energy to be wasted. The common notion about the regulatory biology of denitrification is based on detailed studies of only a few model organisms. Although the gene regulatory networks of these organisms share some common traits, there is a substantial variation in the way organisms tackle transition from aerobic respiration to denitrification, and in the levels they accumulate intermediates. This knowledge, however, only arose from studies of model organisms and there is a need to validate its importance in the natural settings. Denitrification as a sequential reduction of nongaseous nitrate (NO3 -) and nitrite (NO2 -) to gaseous nitric oxide (NO), nitrous oxide (N2O) and dinitrogen gas (N2), is a key process in the nitrogen cycle, yet its two gaseous intermediate products have great impact on the climate (N2O) and the chemistry of the troposphere (NO). In addition to its global forcing, N2O is also destroys stratospheric ozone, and the emission of this gas has attracted the attention of researchers and ecologists. Agricultural soils are the main source of anthropogenic N2O emission and in order to develop mitigation strategies, there is a need for understanding the mechanism of N2O production and reduction. There is ample evidence, that the N2O/(N2O+N2) product ratio of the denitrification process depends on several factors, among which the ambient pH is a dominant driver. Other processes within the nitrogen cycle can also liberate N2O, however, denitrification is the largest source of it, and up to date, there is only one biological sink for this N2O – a multicopper-dependent nitrous oxide reductase (N2OR, NosZ). The enzyme that carries the two-electron reduction of N2O to N2 is located in the bacterial periplasm, where its maturation and assembly takes place. Combining facts of pH dependent N2O reduction in natural settings and the subcellular localization of N2OR I started to investigate the processes laying behind. In Paper I, we have tested the relevance of the observation obtained from model denitrifying bacteria and we do see that phenomena ascribed to them are also occurring in the nature. Moreover, we see that the presence of the nosZ gene does not correspond with the function in over 20% of investigated organisms. The second paper reveals the undescribed bet-hedging survival strategy in the denitrifying bacterium Paracoccus denitrificans, which improves its fitness, minimizes costs of protein expression and has great ecological influence, as the majority of the isogenic bacterial population acts as a strong sink for the N2O greenhouse gas. In Paper III we try to explain why acidic soils are the major source of the N2O. To our understanding the ambient pH hampers the maturation of copper in the N2OR enzyme, thus causes the emissions. The preliminary results, that we have obtained so far, support our hypothesis.Bakterier i naturlig miljø er normalt begrenset av tilgang på substrat, og de utfordres av hyppige endringer i miljøbetingelsene. For å overleve disse endringene må de for det første ha sensorer som merker endringen, og som initierer tilpasningen. Tilpasning er normalt synonymt med produksjon av nye enzymer. Dette koster energi, som er en minimumsfaktor. Overleving (fitness) er derfor ikke bare avhengig av adekvat respons, men også at energiforbruket til dette minimeres. Denitrifiserende bakterier svarer på oksygenmangel ved å uttrykke gener som koder for et sett med enzymer som setter dem i stand til å respirere ved å redusere nitrogen-oksyder. Det regulatoriske nettverket for disse genene er undersøkt i et fåtall modellorganismer, og disse viser noen felles trekk, men betydelig variasjon, som har konsekvenser for deres produksjon av intermediater. Det er et åpenbart behov for å studere denne regulatoriske biologien i flere, og ikke minst mer økologisk relevante organismer.Nitrous Oxide Research Alliance (NORA), a Marie Skłodowska-Curie ITN research project under the EU͛s seventh framework programm

Novel aspects of the ecophysiology of denitrifying bacteria and their roles in N2O emissions

Environmental bacteria are in general limited by nutrient availability, and as the conditions fluctuate rapidly and unpredictably they must adapt or they will not thrive. This requires fast and adequate sensing and responding mechanisms, assuring fitness with minimum investment, as there is not much energy to be wasted. The common notion about the regulatory biology of denitrification is based on detailed studies of only a few model organisms. Although the gene regulatory networks of these organisms share some common traits, there is a substantial variation in the way organisms tackle transition from aerobic respiration to denitrification, and in the levels they accumulate intermediates. This knowledge, however, only arose from studies of model organisms and there is a need to validate its importance in the natural settings. Denitrification as a sequential reduction of nongaseous nitrate (NO3 -) and nitrite (NO2 -) to gaseous nitric oxide (NO), nitrous oxide (N2O) and dinitrogen gas (N2), is a key process in the nitrogen cycle, yet its two gaseous intermediate products have great impact on the climate (N2O) and the chemistry of the troposphere (NO). In addition to its global forcing, N2O is also destroys stratospheric ozone, and the emission of this gas has attracted the attention of researchers and ecologists. Agricultural soils are the main source of anthropogenic N2O emission and in order to develop mitigation strategies, there is a need for understanding the mechanism of N2O production and reduction. There is ample evidence, that the N2O/(N2O+N2) product ratio of the denitrification process depends on several factors, among which the ambient pH is a dominant driver. Other processes within the nitrogen cycle can also liberate N2O, however, denitrification is the largest source of it, and up to date, there is only one biological sink for this N2O – a multicopper-dependent nitrous oxide reductase (N2OR, NosZ). The enzyme that carries the two-electron reduction of N2O to N2 is located in the bacterial periplasm, where its maturation and assembly takes place. Combining facts of pH dependent N2O reduction in natural settings and the subcellular localization of N2OR I started to investigate the processes laying behind. In Paper I, we have tested the relevance of the observation obtained from model denitrifying bacteria and we do see that phenomena ascribed to them are also occurring in the nature. Moreover, we see that the presence of the nosZ gene does not correspond with the function in over 20% of investigated organisms. The second paper reveals the undescribed bet-hedging survival strategy in the denitrifying bacterium Paracoccus denitrificans, which improves its fitness, minimizes costs of protein expression and has great ecological influence, as the majority of the isogenic bacterial population acts as a strong sink for the N2O greenhouse gas. In Paper III we try to explain why acidic soils are the major source of the N2O. To our understanding the ambient pH hampers the maturation of copper in the N2OR enzyme, thus causes the emissions. The preliminary results, that we have obtained so far, support our hypothesis

Competition for electrons favours N2O reduction in denitrifying Bradyrhizobium isolates

Bradyrhizobia are common members of soil microbiomes and known as N-2-fixing symbionts of economically important legumes. Many are also denitrifiers, which can act as sinks or sources for N2O. Inoculation with compatible rhizobia is often needed for optimal N-2-fixation, but the choice of inoculant may have consequences for N2O emission. Here, we determined the phylogeny and denitrification capacity of Bradyrhizobium strains, most of them isolated from peanut-nodules. Analyses of genomes and denitrification end-points showed that all were denitrifiers, but only similar to 1/3 could reduce N2O. The N2O-reducing isolates had strong preference for N2O- over NO3--reduction. Such preference was also observed in a study of other bradyrhizobia and tentatively ascribed to competition between the electron pathways to Nap (periplasmic NO3- reductase) and Nos (N2O reductase). Another possible explanation is lower abundance of Nap than Nos. Here, proteomics revealed that Nap was instead more abundant than Nos, supporting the hypothesis that the electron pathway to Nos outcompetes that to Nap. In contrast, Paracoccus denitrificans, which has membrane-bond NO3- reductase (Nar), reduced N2O and NO3- simultaneously. We propose that the control at the metabolic level, favouring N2O reduction over NO3- reduction, applies also to other denitrifiers carrying Nos and Nap but lacking Nar.Peer reviewe

Влияние глобального стриминга на киноиндустрию и культурные продукты

Внедрение новых технологий в повседневную жизнь по-своему влияет на различные области культуры, включая кино. Это один из самых влиятельных секторов, глобальные сообщения которого доводятся до массовой аудитории по всему миру с помощью различных платформ. В современных условиях, в частности, на фоне ситуации с пандемией Covid-19, широко используются потоковые платформы, которые облегчают предоставление культурных продуктов пользователям, несмотря на наложенные ограничения. Текущие инновации в киноиндустрии показали впечатляющий прогресс и расширение возможностей в несколькихнаправлениях: в распространении и продвижении новейшей продукции, предоставлении разнообразного контента из основных каталогов фильмов, постоянное совершенствование алгоритмов, которые рекомендуют фильмы с похожими названиями в зависимости от индивидуальных вкусовых предпочтений пользователей. Всё вышеназванное позволяет расширить аудиторию зрителей, получающих доступ к контенту через самые разные устройства. Наблюдаемые обстоятельства приводят к изменениям в данном секторе, к новым потребительским практикам. Автор статьи устанавливает взаимозависимость между влиянием глобальных сообщений, которое основные платформы, такие как Netflix, Amazon Prime Video, Apple TV и другие, оказывают посредством предоставления доступа к фильмам из разных стран, с одной стороны, и того, и изменениями кинорынка, с другой. Рассмотрены конкретные модели воздействия, с помощью которых им удается привлекать и удерживать внимание аудитории. Одна из составляющих процесса создания богатой культуры глобального сообщества – распространение качественных фильмов, способствующее развитию высоких стандартов эстетики и творческого восприятия. Платформы предоставляют возможность зрителям всего мира познакомиться с отечественными кинопроизводствами и, таким образом, расширить свой кругозор. В центре внимания появившихся потоковых медиа находятся и вызывают большой интерес аудитории серьезные вопросы, связанные с качеством предлагаемых фильмов, а также с особенностями их презентации на стриминговых платформах.The entry of new technologies into daylife has its own impact on various areas of culture, including cinema. It is one of the most influential sectors, whose global messages reach a mass audience around the world, aided by various platforms. Although the development of the current situation with the Covid-19 pandemic and ongoing daily updates, as a result, there are a large-scale use of streaming platforms, which facilitate the provision of cultural products despite the imposed restrictions. Current innovations and changes surrounding film industry have revealed the impressive progression and capabilities in several different directions – distribution and promotion of new and original products, providing a variety of content from major film catalogs, continuously improving algorithms, which recommend different similar movie title according to individual taste. Mentioned above is leading to large-scale of viewers through a variety of devices. The observed circumstances leads to changes in the specific sector, as well as to new consumer practices. This article combine global messages and impact that major platforms such as Netflix, Amazon Prime Video, Apple TV and more, creates through specific movies from different countries and the ways in which film markets are changing. The specific behaviors through which they successfully manage to attract and retain the attention of the audience are considered. Part of the process of creating a rich global culture is presence and distribution of quality movies, whose messages to cultivate high standards of esthetics and creative perception. The platforms provides an opportunity for viewers around the world to experience domestic film productions and thus enrich their own horizons. The focus of emerged streaming media and the great interest they arouse in the audience are serious questions related to the quality of the offered films, as well as the way they are presented

Denitrification as an N2O sink

The strong greenhouse gas nitrous oxide (N2O) can be emitted from wastewater treatment systems as a byproduct of ammonium oxidation and as the last intermediate in the stepwise reduction of nitrate to N2 by denitrifying organisms. A potential strategy to reduce N2O emissions would be to enhance the activity of N2O reductase (NOS) in the denitrifying microbial community. A survey of existing literature on denitrification in wastewater treatment systems showed that the N2O reducing capacity (VmaxN2O/N2) exceeded the capacity to produce N2O (VmaxNO3/N2O) by a factor of 2e10. This suggests that denitrification can be an effective sink for N2O, potentially scavenging a fraction of the N2O produced by ammonium oxidation or abiotic reactions. We conducted a series of incubation experiments with freshly sampled activated sludge from a wastewater treatment system in Oslo and found that the ratio a ¼ VmaxN2O/N2/VmaxNO3/N2O fluctuated between 2 and 5 in samples taken at intervals over a period of 5 weeks. Adding a cocktail of carbon substrates resulted in increasing rates, but had no significant effect on a. Based on these results e complemented with qPCR and metaproteomic data e we discuss whether the overcapacity to reduce N2O can be ascribed to gene/protein abundance ratios (nosZ/nir), or whether in-cell competition between the reductases for electrons could be of greater importance.publishedVersio