The NarX-NarL two-component system regulates biofilm formation, natural product biosynthesis, and host-associated survival in Burkholderia pseudomallei

Burkholderia pseudomallei is a saprophytic bacterium endemic throughout the tropics causing severe disease in humans and animals. Environmental signals such as the accumulation of inorganic ions mediates the biofilm forming capabilities and survival of B. pseudomallei. We have previously shown that B. pseudomallei responds to nitrate and nitrite by inhibiting biofilm formation and altering cyclic di-GMP signaling. To better understand the roles of nitrate-sensing in the biofilm inhibitory phenotype of B. pseudomallei, we created in-frame deletions of narX (Bp1026b_I1014) and narL (Bp1026b_I1013), which are adjacent components of a conserved nitrate-sensing two-component system. We observed transcriptional downregulation in key components of the biofilm matrix in response to nitrate and nitrite. Some of the most differentially expressed genes were nonribosomal peptide synthases (NRPS) and/or polyketide synthases (PKS) encoding the proteins for the biosynthesis of bactobolin, malleilactone, and syrbactin, and an uncharacterized cryptic NRPS biosynthetic cluster. RNA expression patterns were reversed in ∆narX and ∆narL mutants, suggesting that nitrate sensing is an important checkpoint for regulating the diverse metabolic changes occurring in the biofilm inhibitory phenotype. Moreover, in a macrophage model of infection, ∆narX and ∆narL mutants were attenuated in intracellular replication, suggesting that nitrate sensing contributes to survival in the host.

Synthesizing the impacts of baseflow contribution on concentration–discharge (<i>C</i>–<i>Q</i>) relationships across Australia using a Bayesian hierarchical model

Understanding concentration–discharge (C–Q) relationships can inform catchment solute and particulate export processes. Previous studies have shown that the extent to which baseflow contributes to streamflow can affect C–Q relationships in some catchments. However, the current understanding on the effects of baseflow contribution in shaping the C–Q patterns is largely derived from temperate catchments. As such, we still lack quantitative understanding of these effects across a wide range of climates (e.g. arid, tropical and subtropical). The study aims to assess how baseflow contributions, as defined by the median and the range of daily baseflow indices within individual catchments (BFI_m and BFI_range, respectively), influence C–Q slopes across 157 catchments in Australia spanning five climate zones. This study focuses on six water quality variables: electrical conductivity (EC), total phosphorus (TP), soluble reactive phosphorus (SRP), total suspended solids (TSS), the sum of nitrate and nitrite (NOx) and total nitrogen (TN). The impact of baseflow contributions is explored with a novel Bayesian hierarchical model. For sediments and nutrient species (TSS, NOx, TN and TP), we generally see largely positive C–Q slopes, which suggest a dominance of mobilization export patterns. Further, for TSS, NOx and TP we see stronger mobilization (steeper positive C–Q slopes) in catchments with higher values in both the BFI_m and BFI_range, as these two metrics are positively correlated for most catchments. The enhanced mobilization in catchments with higher BFI_m or BFI_range is likely due to the more variable flow pathways that occur in catchments with higher baseflow contributions. These variable flow pathways can lead to higher concentration gradients between low flows and high flows, where the former is generally dominated by groundwater/slow subsurface flow while the latter by surface water sources, respectively. This result highlights the crucial role of flow pathways in determining catchment exports of solutes and particulates. Our study also demonstrates the need for further studies on how the temporal variations of flow regimes and baseflow contributions influence flow pathways and the potential impacts of these flow pathways on catchment C–Q relationships.

Biophysical and in silico characterization of NrtA: A protein-based host for aqueous nitrate and nitrite recognition

Nitrate and nitrite are key components of the global nitrogen cycle. As such, Nature has evolved proteins as biological supramolecular hosts for the recognition, translocation, and transformation of both nitrate...

Identification of the nitrate and nitrite content in leafy vegetables from the city of Zliten: تحديد محتوى النترات والنتريت في الخضار الورقية من مدينة زليتن

The study identifies the nitrate (NO3) and nitrite (NO2) content in leafy vegetables (parsley, chard, coriander) in three agricultural areas in Zliten (Azdo, Dafniya, Madjer) using the colorimeter dr / 980 device, and assesses whether the content is within the comparatively with allowable concentrations. The results obtained from this study show that the nitrate concentrations in all samples examined are within the global standards, with the highest level of 5.5 ppm found in chard samples collected from the area of Azdo. As for nitrite, the concentrations found in the studied samples are higher than nitrate concentrations. Overall, the nitrate and nitrite content are found to be within the permitted concentrations based on international standards, where the highest concentration of nitrite of 60 ppm is recorded in parsley samples from the Dafniya area.

Analysis of biological methods for quarry wastewater treatment from nitrogen compounds

Деятельность горнодобывающих предприятий неотрывно сопряжена с ведением взрывных работ. В настоящее время наиболее распространенными взрывчатыми веществами являются эмульсионные взрывчатые вещества, граммониты, амоналы, аммониты и другие взрывчатые вещества, содержащие нитрат аммония, который в процессе взрывания переходит в сточные воды в форме нитрат- и нитрит-ионов, а также ионов аммония. Превышение предельно допустимой концентрации азотных соединений в водных объектах может приводить к эвтрофикации. В результате данного процесса происходит нарушение экологического баланса водоемов, а именно увеличение численности различных гидробионтов, уменьшение прозрачности воды и содержания растворенного кислорода. Помимо этого в водоемах осуществляется преобразование нитратной формы азота в нитритную, которая негативно воздействует на нервную и сердечно-сосудистую системы человека при употреблении воды из такого водоема. На данный момент существуют физико-химические, химические и биологические методы очистки вод от азотных соединений. Использование каждого из перечисленных методов обуславливается параметрами карьерных сточных вод и требованиями, предъявляемыми к качеству очистки. Цель работы. Целью работы является обзор методов биологической очистки, которые могут применяться для удаления соединений азота из карьерных сточных вод, а также определение наиболее перспективного метода при условии большого объема образования карьерных сточных вод. Методы исследования. Методы исследования включают в себя анализ и сравнение биологических методов очистки, которые могут использоваться для удаления азотных соединений из образующихся сточных вод в карьере. Результаты работы. Рассмотрены различные виды процессов и систем, включая процесс нитрификации и денитрификации, Anammox-процесс, фито-очистные системы, биоплато, биопруды и системы микроводорослей. Приведены факторы, влияющие на эффективность работы данных процессов и систем, а также дана сравнительная характеристика с выделением достоинств и недостатков каждого из них. Наиболее предпочтительным методом биологической очистки большого объема образующихся карьерных сточных вод признан метод комплексной очистки по типу constructedwetlands с комплексным применением видов высшей и низшей растительности. The activities of mining enterprises are inextricably linked with the conduct of blasting operations. Currently, the most common explosives are emulsion explosives, grammonites, amons, ammonites and other explosives containing ammonium nitrate, which, during the blasting process, passes into wastewater in the form of nitrate and nitrite ions, as well as ammonium ions. Exceeding the maximum permissible concentration of nitrogen compounds in water bodies can lead to eutrophication. As a result of this process, there is a violation of the ecological balance of reservoirs, as well as an increase in the number of various hydrobionts, a decrease in the transparency of water and the content of dissolved oxygen. In addition, the nitrate form of nitrogen is converted into nitrite in reservoirs, which negatively affects the nervous and cardiovascular system of a person when drinking water from such a reservoir. At the moment, there are physico-chemical, chemical and biological methods of water treatment from nitrogen. The use of each of these methods is determined by parameters of quarry wastewater and the requirements for treatment quality. Aim. The aim of the work is to review the methods of biological purification that are used for nitrogen compounds from quarry wastewater. Methods. The research methods include the analysis and comparison of biological treatment methods. Results. The factors affecting the efficiency of these processes and systems are presented, as well as these comparative characteristics, highlighting the advantages and disadvantages of each of them. The most preferred biological treatment method of a large volume of formed quarry wastewater is the recognized methods of complex treatment according to the type of constructed wetlands with the complex use of higher and lower plant species.

Coastal Hypoxia Drives Microbial Diversity: Elucidation through 16S rRNA Amplicon Sequencing

The formation of oxygen-depleted zones in the bottom waters is one of the most widespread phenomena in coastal areas. Upwelling episodes occurring along the west coast of India due to the southwest monsoon lead to an increase in biological productivity which further lowers the dissolved oxygen in the upwelled waters, which intensifies annually between June and October. Here, we have determined the changes in the microbial community in response to the varying oxygen levels and other physicochemical parameters at the Candolim Time Series Station using high-throughput sequencing. Amplicon Sequence Variants across all the samples collected in different seasons were mostly affiliated to the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Chloroflexi, Firmicutes and Planctomycetes, with the most dominant being Proteobacteria (21-41%). Statistical analysis revealed that microbial diversity differed significantly with changing DO, ammonia, nitrate and nitrite concentrations during different seasons. The microbial community shift due to seasonal hypoxia results in the differential biogeochemical cycling of essential nutrients with certain years seeing redox conditions up to sulphate reduction, while certain years seeing only nitrogen loss. Future scenario of global warming will serve as a big challenge for understanding the role of microbial diversity and its implications in the cycling of natural elements.

Azospira inquinata sp. nov., a nitrate-reducing bacterium of the family Rhodocyclaceae isolated from contaminated groundwater

Two novel Gram-stain-negative bacterial strains, Azo-3T and Azo-2, were isolated from a toluene-producing enrichment culture that originated from contaminated groundwater at a site in southeast Louisiana (USA). Cells are non-spore forming straight to curved rods with single polar flagella. Strains Azo-3T and Azo-2 are oxidase-positive, catalase-negative, use nitrate and nitrite as electron acceptors, and are able to fix nitrogen. Poly-β-hydroxybutyrate storage granules are produced. Dominant fatty acids when grown in R2A medium at 37 °C are C16:0, summed feature 3 (C16:1 ω7c and/or C15:0 iso 2OH), C17:0 cyclo and C18:1 ω7c. 16S rRNA gene sequence based phylogenetic analysis indicated that the strains cluster within the family Rhodocyclaceae , class Betaproteobacteria , most closely related to but distinct from type strains of the species Azospira oryzae (96.94% similarity) and Azospira restricta (95.10% similarity). Complete genome sequences determined for strains Azo-3T and Azo-2 revealed DNA G+C content of 62.70 mol%. Genome-wide comparisons based on average nucleotide identity by orthology and estimated DNA–DNA hybridization values combined with phenotypic and chemotaxonomic traits and phylogenetic analysis indicate that strains Azo-3T and Azo-2 represent a novel species within the genus Azospira for which the name Azospira inquinata sp. nov. is proposed. The type strain of Azospira inquinata is Azo-3T (=NRRL B-65590T=DSM 112046T).

Nitrogen Removal by an Anaerobic Iron-Dependent Ammonium Oxidation (Feammox) Enrichment: Potential for Wastewater Treatment

Nitrogen pollution in water is a growing concern. Anthropogenic activities have increased the amount of nitrogen released into watercourses, which harms human health and the environment, and causes serious problems, such as eutrophication. Feammox is a recently discovered biological pathway associated with the nitrogen cycle that has gained scientific interest. This process couples anaerobic ammonium oxidation with iron reduction. This work presents a study on the Feammox mechanism from the enrichment of an activated sludge obtained from a sewage treatment plant. The enrichment was carried out at neutral pH to study the N2 pathway, that is, the Feammox process with the oxidation of ammonium (NH4+) directly to N2. In addition, different sources of iron were studied: iron chloride (FeCl3); ferrihydrite; and goethite. The characterization of the sludge showed the genes associated with ammonia monooxygenase, nitrate and nitrite reductases processes, along with relevant microbial species. The enrichment, carried out for 42 days and monitored every 14 days, showed that FeCl3 as a source of Fe was more effective for the coupled process of oxidation of NH4+ and the reduction of Fe(III) to Fe(II). At the end of the enrichment period, a removal of 31% and 32.2% of NH4+, and an increase in Fe(II) concentration by 52.4 and 63.9 times regarding the initial value were achieved in aerobic and anaerobic sludge, respectively. This study provides information on the potential of Feammox in the removal of N from wastewater, and the oxidation/reduction yields in the initial enrichment phase.