Laboratory studies on the infectivity of human respiratory viruses: Experimental conditions, detections, and resistance to the atmospheric environment.

The environmental stability of infectious viruses in the laboratory setting is crucial to the transmission potential of human respiratory viruses. Different experimental techniques or conditions used in studies over the past decades have led to diverse understandings and predictions for the stability of viral infectivity in the atmospheric environment. In this paper, we review the current knowledge on the effect of simulated atmospheric conditions on the infectivity of respiratory viruses, mainly focusing on influenza viruses and coronaviruses, including severe acute respiratory syndrome coronavirus 2 and Middle East respiratory syndrome coronavirus. First, we summarize the impact of the experimental conditions on viral stability; these involve the methods of viral aerosol generation, storage during aging and collection, the virus types and strains, the suspension matrixes, the initial inoculum volumes and concentrations, and the drying process. Second, we summarize and discuss the detection methods of viral infectivity and their disadvantages. Finally, we integrate the results from the reviewed studies to obtain an overall understanding of the effects of atmospheric environmental conditions on the decay of infectious viruses, especially aerosolized viruses. Overall, this review highlights the knowledge gaps in predicting the ability of viruses to maintain infectivity during airborne transmission.

The imbalance between N2O production and reduction by multi-microbial communities determines sedimentary N2O emission potential in the Pearl River Estuary.

Denitrification is the dominant process of nitrogen removal and nitrous oxide (N2O) emissions in estuarine ecosystems. However, little is known regarding the microbial mechanism of the production and reduction of N2O in estuaries. We investigated in situ dissolved N2O as well as potential N2O production rate (NPR), reduction rate (NRR), and emission rate (NER), and key functional genes related to N2O transformation of denitrification in the Pearl River Estuary. Higher N2O emission potential was found in the upstream and midstream regions with higher NPR and lower NRR values. In contrast, higher NRR values were detected in downstream. Notably, nirS and nirK type N2O producers dominated the upstream zone, whereas abundant N2O reducers, especially nosZ II type N2O reducers, were observed in downstream. Most importantly, the gene abundance ratio (Rnir/nosZ) was significantly correlated with the N2O emission potential (Re). Niche differentiation between N2O producers and N2O reducers from upstream to downstream affected N2O emission potential. This study highlights the N2O emission potential in estuarine sediments is determined by an imbalance between N2O production and the reduction of multi-bacterial communities.

[Normalization of the ratio of nitric oxide and peroxynitrite by promoting eNOS dimer activity is a new direction for diabetic nephropathy treatment].

Diabetic nephropathy is a microvascular complication of diabetes. Its etiology involves metabolic disorder-induced endothelial dysfunction. Endothelium-derived nitric oxide (NO) plays an important role in a number of physiological processes, including glomerular filtration and endothelial protection. NO dysregulation is an important pathogenic basis of diabetic nephropathy. Hyperglycemia and dyslipidemia can lead to oxidative stress, chronic inflammation and insulin resistance, thus affecting NO homeostasis regulated by endothelial nitric oxide synthase (eNOS) and a conglomerate of related proteins and factors. The reaction of NO and superoxide (O2.-) to form peroxynitrite (ONOO-) is the most important pathological NO pathway in diabetic nephropathy. ONOO- is a hyper-reactive oxidant and nitrating agent in vivo which can cause the uncoupling of eNOS. The uncoupled eNOS does not produce NO but produces superoxide. Thus, eNOS uncoupling is a critical contributor of NO dysregulation. Understanding the regulatory mechanism of NO and the effects of various pathological conditions on it could reveal the pathophysiology of diabetic nephropathy, potential drug targets and mechanisms of action. We believe that increasing the stability and activity of eNOS dimers, promoting NO synthesis and increasing NO/ONOO- ratio could guide the development of drugs to treat diabetic nephropathy. We will illustrate these actions with some clinically used drugs as examples in the present review.

Variations in nitrogen removal rates and microbial communities over sediment depth in Daya Bay, China.

Depth-related variations in the activities, abundances, and community composition of denitrification and anaerobic ammonia oxidation (anammox) bacteria in coastal sediment cores remain poorly understood. In this study, we used 15N-labelled incubation, quantitative polymerase chain reaction (qPCR), and high-throughput sequencing techniques to reveal the structure and function of denitrifiers and anammox bacteria in sediment cores (almost 100 cm depth) collected in winter and summer from four locations in Daya Bay. The results indicated that the activities and abundances of both denitrifiers and anammox bacteria were detected even in deeper sediments with low concentrations of dissolved inorganic nitrogen (DIN). The potential rates, abundances, and community compositions of denitrifiers and anammox bacteria only varied spatially. In the surface sediment (top 2 cm), denitrifiers had significantly higher activities and abundances than anammox bacteria, but the relative contribution of anammox bacteria to nitrogen loss increased to >60% in the subsurface sediments. Phylogenetic analysis revealed that nirS-type denitrifiers were affiliated to 10 different clusters and Candidatus Scalindua dominated the anammox community in the whole sediments. Furthermore, both denitrification and anammox bacterial communities in the subsurface sediments were distinct from those in the surface sediments. Coupled nitrification and denitrification or anammox may play significant roles in removing fixed N, and the availability of electronic acceptors (e.g. nitrite and nitrate) strongly influenced the N loss activities in the subsurface sediment, emphasising its role as a sink for buried N.

Shift of DNRA bacterial community composition in sediment cores of the Pearl River Estuary and the impact of environmental factors.

Dissimilatory nitrate reduction to ammonia (DNRA) process, competing with denitrification and anaerobic ammonia oxidation (anammox) for nitrate, is an important nitrogen retention pathway in the environment. Previous studies on DNRA bacterial diversity and composition focused on the surface sediments in estuaries, but studies on the deep sediments are limited, and the linkage between DNRA community structure and complex estuarine environment remains unclear. In this study, through high-throughput sequencing of nrfA gene followed by high-resolution sample inference, we examined spatially and temporally the composition and diversity of DNRA bacteria along a salinity gradient in five sediment cores of the Pearl River Estuary (PRE). We found a higher diversity and richness of DNRA bacteria in sediments with lower organic carbon, where sea water intersects fresh water. Moreover, the DNRA bacterial communities had the specific spatially distribution coupling with their metabolic difference along the salinity gradient of the Pearl River Estuary, but no obvious difference along the sediment depth. The distribution of DNRA bacteria in the PRE was largely driven by various environmental factors, including salinity, Oxidation-Reduction Potential (ORP), ammonium, nitrate and Corg/NO3-. Furthermore, dominant DNRA bacteria were found to be the key populations of DNRA communities in the PRE sediments by network analysis. Collectively, our results showed that niche difference of DNRA bacteria indeed occurs in the Pearl River Estuary.

Anaerobic Ammonium Oxidation in Acidic Red Soils.

Anaerobic ammonium oxidation (anammox) has been proven to be an important nitrogen removal process in terrestrial ecosystems, particularly paddy soils. However, the contribution of anammox in acidic red soils to nitrogen loss has not been well-documented to date. Here, we investigated the activity, abundance, and distribution of anammox bacteria in red soils collected from nine provinces of Southern China. High-throughput sequencing analysis showed that Candidatus Brocadia dominates the anammox bacterial community (93.03% of sequence reads). Quantification of the hydrazine synthase gene (hzsB) and anammox 16S rRNA gene indicated that the abundance of anammox bacteria ranged from 6.20 × 106 to 1.81 × 109 and 4.81 × 106 to 4.54 × 108 copies per gram of dry weight, respectively. Contributions to nitrogen removal by anammox were measured by a 15N isotope-pairing assay. Anammox rates in red soil ranged from 0.01 to 0.59 nmol N g-1 h-1, contributing 16.67-53.27% to N2 production in the studied area, and the total amount of removed nitrogen by anammox was estimated at 2.33 Tg N per year in the natural red soils of southern China. Pearson correlation analyses revealed that the distribution of anammox bacteria significantly correlated with the concentration of nitrate and pH, whereas the abundance and activity of anammox bacteria were significantly influenced by the nitrate and total nitrogen concentrations. Our findings demonstrate that Candidatus Brocadia dominates anammox bacterial communities in acidic red soils and plays an important role in nitrogen loss of the red soil in Southern China.