Microbial Response to Coastal-Offshore Gradients in Taiwan Straits: Community Metabolism and Total Prokaryotic Abundance as Potential Proxies.

Located between the South and the East China Sea, the Taiwan Straits (TWS) are a marine shelf-channel area, with unique hydrological and geomorphological features affected by rivers inflow and with recent algal blooms with red tide events. This study aimed at assessing microbial distribution and function and their modulation in response to environmental gradients. Surface (0.5 m) water samples from 16 stations along five north to south transects were collected; total prokaryotic abundance by epifluorescence microscope and carbon substrate utilization patterns by Biolog Ecoplates were estimated. Spatially, a patchy microbial distribution was found, with the highest microbial metabolic levels and prokaryotic abundance in the TWS area between Minjiang River estuary and Pingtan Island, and progressive decreases towards offshore stations. Complex carbon sources and carbohydrates were preferentially metabolized. This study provides a snapshot of the microbial abundance and activity in TWS as a model site of aquatic ecosystems impacted from land inputs; obtained data highlights that microbial metabolism is more sensitive than abundance to environmental changes.

Regulation of the Nutrient Cycle Pathway and the Microbial Loop Structure by Different Types of Dissolved Organic Matter Decomposition in Lakes.

To explore the effect of different types of dissolved organic matter (DOM) decomposition on nutrient cycling pathways and the microbial loop, four lakes with different DOM sources were investigated monthly. In Lake Tangxun, Dolichospermum decay released highly labile dissolved organic nitrogen into the water column. This induced bacterial organic nitrogen decomposition, as indicated by the increased abundance of gltB, gltD, gdh, and glnA as well as aminopeptidase activity. Genes associated with dissimilatory nitrate reduction to ammonium further fueled ammonium accumulation, driving Microcystis blooms in the summer. In Lake Zhiyin, fish bait deposits (high nitrogen, similar to Dolichospermum detritus) also caused Microcystis blooms. Detritus from Microcystis decomposition then produced high levels of labile dissolved organic phosphorus, inducing phosphatase activity and increasing soluble reactive phosphorus concentrations from September to April in Lakes Tangxun and Zhiyin. The high refractory DOM from macrophytes in Lake Houguan led to insufficient nutrient availability, leading to nutrient mutualism between algae and bacteria. The high levels of labile dissolved organic carbon from terrestrial detritus in Lake Yandong increased bacterial biomass and production, resulting in low chlorophyll content due to the competitive relationship between algal and bacterial nutrient requirements. Therefore, different DOM compositions induce unique connections among available nutrients, algae, and bacteria in the microbial loop.

Interactions between Phosphorus Enrichment and Nitrification Accelerate Relative Nitrogen Deficiency during Cyanobacterial Blooms in a Large Shallow Eutrophic Lake.

Regime shifts between nitrogen (N) and phosphorus (P) limitation, which trigger cyanobacterial succession, occur in shallow eutrophic lakes seasonally. However, the underlying mechanism is not yet fully illustrated. We provide a novel insight to address this from interactions between sediment P and nitrification through monthly field investigations including 204 samples and microcosm experiments in Lake Chaohu. Total N to P mass ratios (TN/TP) varied significantly across seasons especially during algal bloom in summer, with the average value being 26.1 in June and descending to 7.8 in September gradually, triggering dominant cyanobacterial succession from Microcystis to Dolichospermum. The regulation effect of sediment N/P on water column TN/TP was stronger in summer than in other seasons. Iron-bound P and alkaline phosphatase activity in sediment, rather than ammonium, contributed to the higher part of nitrification. Furthermore, our microcosm experiments confirmed that soluble active P and enzymatic hydrolysis of organic P, accumulating during algal bloom, fueled nitrifiers and nitrification in sediments. These processes promoted lake N removal and led to relative N deficiency in turn. Our results highlight that N and P cycles do not exist independently but rather interact with each other during lake eutrophication, supporting the dual N and P reduction program to mitigate eutrophication in shallow eutrophic lakes.

Metagenomic insights into feasibility of agricultural wastes on optimizing water quality and natural bait by regulating microbial loop.

Effective screening feed substitutes for improving water quality in aquaculture systems has become a trending research topic now. In this study, three typical organic agricultural wastes, including sugar cane bagasse (SC), coconut shell powder (CS), and corn cob powder (CC), were selected to evaluate their potential roles on the optimization of water quality and natural bait compared to aquafeeds. Fish feed resulted in the highest growth rate of fish but the worst water quality. Organic detritus addition markedly improved the water quality, especially soluble reactive phosphorus (SRP, decrease of 56-61%) and ammonium (decrease of 16% in SC, 47% in CC). Specially, SC induced core microbes to mediate nutrients transformation and recycling (N2-fixation, ammonification, nitrification, dissimilatory nitrate reduction to ammonia and organic nutrients decomposition), which facilitated the primary productivity based on their positive relationships. This further reduced the available nutrients (especially SRP) in the water and built a mutually beneficial microbial loop. In addition, SC addition increased the abundance of genes involved in amino acids biosynthesis pathways, photosynthesis, and carbon fixation. These results led to energy transfer to higher trophic levels. The addition of CC had a better effect than SC in terms of lower nitrogen levels and a higher fish growth rate (19% in CC, 5% in SC). However, low temperatures and carbon accumulation jointly drive the anaerobic decomposition, resulting in unhealthy microbial loops and low fish growth rates. In contrast to the direct consumption of fish feed, organic detritus can induce more natural bait to provide food for fish by regulating the microbial loop, as showed by the microbial community composition in the water and fish gut. To comprehensively assess water quality, natural bait, and fish growth and quality, certain organic detritus should be considered as an auxiliary material to partially replace feed for healthy and sustainable aquaculture systems.

Mechanisms and risks of joint control of nitrogen and phosphorus through sediment capping technology in a pilot-scale study.

Purpose: Nitrogen (N) and phosphorus (P) are the key elements leading to eutrophication, and it is important to jointly control N and P release from sediments into the water column. Methods: Different mixed materials including P sorbent, natural organic carbon (C), and an oxidizing agent were applied in a 1-year pilot-scale experiment. Results: The addition of iron-rich (IR) clay and Phoslock agent promoted the formation of iron bound P (Fe(OOH)~P) and calcium bound P (CaCO3~P) in sediments, respectively. IR clay offered more advantages in immobilization of phosphorus as refractory P, and the Phoslock agent more effectively reduced the risk of P release into water, which was expressed as a low equilibrium P concentration (EPC0). Mixtures of sugarcane (SU) detritus and IR clay exhibited high carbohydrate (CHO) contents, which further fuelled both denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This indicated that the SU dosage should be controlled to avoid DNRA over denitrification. Attention should be given to the fact that SU introduction significantly promoted the generation of an anaerobic state, leading to the desorption and release of Fe(OOH)~P, which could be alleviated by using Oxone. Multienzyme activity analysis showed that P and N transformation shifted from P desorption to organic P hydrolysis and from ammonification to denitrification and DNRA, respectively. Conclusion: We recommend the use of P sorbent and organic C combined with oxidizing agents as effective mixed materials for sediment remediation, which could enhance P adsorption and provide electron donors for denitrification, while also avoiding the generation of anoxia.

Nutrients regeneration pathway, release potential, transformation pattern and algal utilization strategies jointly drove cyanobacterial growth and their succession.

In order to better understand the contribution of nutrients regeneration pathway, release potential and transformation pattern to cyanobacterial growth and succession, 7 sampling sites in Lake Chaohu with different bloom degree were studied every two months from February to November 2018. The carbon, nitrogen (N) and phosphorus (P) forms or fractions in surface, interstitial water and sediments as well as extracellular enzymatic activities, P sorption, specific microbial abundance and community composition in sediments were analyzed. P regeneration pathway was dominated by iron-bound P desorption and phosphorus-solubilizing bacteria solubilization in severe-bloom and slight-bloom area respectively, which both resulted in high soluble reactive phosphorus (SRP) accumulation in interstitial water. However, in severe-bloom area, higher P release potential caused the strong P release and algal growth, compared to slight-bloom area. In spring, P limitation and N selective assimilation of Dolichospermum facilitated nitrate accumulation in surface water, which provided enough N source for the initiation of Microcystis bloom. In summer, the accumulated organic N in Dolichospermum cells during its bloom was re-mineralized as ammonium to replenish N source for the sustainable development of Microcystis bloom. Furthermore, SRP continuous release led to the replacement of Dolichospermum by Microcystis with the advantage of P quick utilization, transport and storage. Taken together, the succession from Dolichospermum to Microcystis was due to both the different forms of N and P in water column mediated by different regeneration and transformation pathways as well as release potential, and algal N and P utilization strategies.

The Mycobacterium tuberculosis regulatory network and hypoxia.

We have taken the first steps towards a complete reconstruction of the Mycobacterium tuberculosis regulatory network based on ChIP-Seq and combined this reconstruction with system-wide profiling of messenger RNAs, proteins, metabolites and lipids during hypoxia and re-aeration. Adaptations to hypoxia are thought to have a prominent role in M. tuberculosis pathogenesis. Using ChIP-Seq combined with expression data from the induction of the same factors, we have reconstructed a draft regulatory network based on 50 transcription factors. This network model revealed a direct interconnection between the hypoxic response, lipid catabolism, lipid anabolism and the production of cell wall lipids. As a validation of this model, in response to oxygen availability we observe substantial alterations in lipid content and changes in gene expression and metabolites in corresponding metabolic pathways. The regulatory network reveals transcription factors underlying these changes, allows us to computationally predict expression changes, and indicates that Rv0081 is a regulatory hub.

Mutual Dependence of Nitrogen and Phosphorus as Key Nutrient Elements: One Facilitates Dolichospermum flos-aquae to Overcome the Limitations of the Other.

Dolichospermum flos-aquae (formerly Anabaena flos-aquae) is a diazotrophic cyanobacterium causing harmful blooms worldwide, which is partly attributed to its capacity to compete for nitrogen (N) and phosphorus (P). Preventing the blooms by reducing P alone or both N and P has caused debate. To test the effects alone and together on the growth of cyanobacteria, we performed culture experiments in different eutrophication scenarios. N2 fixation in terms of heterocyst density, nitrogenase activity and nifH expression increased significantly in P-replete cultures, suggesting that P enrichment facilitates N2 fixation. Correspondingly, the expression of genes involved in P uptake, e.g., those involved in P-transport ( pstS) and the hydrolysis of phosphomonoesters ( phoD), was upregulated in P-deficient cultures. Interestingly, N addition enhanced not only the expression of these genes but also polyphosphate formation and alkaline phosphatase activity in P-deficient cultures relative to the P-replete cultures, as evidenced by qualitative (enzyme-labeled fluorescence) and quantitative (fluorogenic spectrophotometry) measurements. Furthermore, after N addition, cell activity and growth increased in the P-deficient cultures, underscoring the risk of N enrichment in P-limited systems. The eco-physiological responses shown here help further our understanding of the mechanism of N and P colimitation and underscore the importance of dual N and P reduction in controlling cyanobacterial blooms.

Photo-induced phosphate released from organic phosphorus degradation in deionized and natural water.

The photodegradation of organic phosphorus is one of the most important processes of the phosphorus cycle by which phosphate is regenerated in the water environment. In this study, the influence of direct photolysis or indirect photolysis of organic phosphorus using natural photosensitizers on the released phosphate was examined in deionized and natural water under ultraviolet (UV) irradiation using diazinon as the organic phosphorus model. Phosphate was released when diazinon was exposed to UV light, and the solution pH also exhibited distinct influences on the phosphate that was released from diazinon photodegradation. When the natural photosensitizers were added, the amount of phosphate released increased significantly because of the diazinon indirect photodegradation by reactive species, such as the hydroxyl radical generated by NO3- and Fe3+. However, humic acid and HCO3- inhibited the phosphate released by a radical scavenging effect. When natural water was spiked with diazinon, the phosphate that was released in natural water was higher than that of the control or deionized water, and the phosphate that was released was inhibited when isopropanol was added to the reaction. In addition, the formation of hydroxyl radicals (˙OH) in the natural water systems was identified from the photoluminescence spectra using coumarin as the trapping molecule, and the steady-state concentration of ˙OH in natural water was 3.07 ± 0.57 × 10-16 M under UV irradiation. All of these results indicated that direct and indirect photolysis degradation of organic phosphorus significantly impacts the release of phosphate in surface waters.

Photodissociation dynamics of superexcited O2: dissociation channels O(5S) vs. O(³S).

The photodissociation dynamics of O2, O2 + hυ → O((3)P) + O(2p(3)((4)S)3s, (3)S/(5)S), has been studied by combining the XUV laser pump / UV laser probe and velocity map imaging methods in the photon energy range 14.64-15.20 eV. The fragment yield spectra of O((3)S) and O((5)S) and their velocity map images have been recorded using the state-selective (1+1) REMPI method to detect the fragments. The fragment yield spectra show resolved fine structure that arises from the predissociated Rydberg states I, I' and I″ ((3)Π(Ω = 0,1,2)). The branching ratios between the two decay channels have been measured by one-photon ionization of the fragments O((3)S) and O((5)S) simultaneously. It is surprising to find that the dissociation cross sections for the production of O((5)S) are larger than, or comparable to, those of O((3)S) for the I and I' states, while the cross sections for the production of O((5)S) are smaller than those of O((3)S) for the I″ state. All fragments O((5)S) arise from perpendicular transitions, which provides direct experimental evidence about the symmetry assignments of the states I, I' and I″ excited in this energy region. Although most of the fragments O((3)S) arise from perpendicular transitions, some of them are from parallel transitions. Based on the calculated ab initio potential energy curves, we propose that the neutral dissociation into O((3)P) + O((3)S) occurs mainly via the interaction of the Rydberg states I, I', and I″ with the vibrational continuum of the diabatic 8(3)Π(u) state (1π(u)⁻¹(a4Π(u))3sσ(g), ³Π(u)), while the neutral dissociation into O((3)P) + O((5)S) occurs mainly via the interaction of Rydberg states I, I', and I″ with the diabatic 7(3)Π(u) (1π(g)⁻¹(X²Π(g))3pσ(u), ³Π(u)).

Relationship between eutrophication and greenhouse gases emission in shallow freshwater lakes.

In shallow lakes, there are complex relationships between lake eutrophication and greenhouse gas emissions that deserve to be studied, which are important for solving lake eutrophication, slowing down climate warming, and reducing carbon emissions. In order to explore the relationship and mechanism between eutrophication and greenhouse gases (GHGs), the net GHGs emission flux and transformation of carbon, and nitrogen in 45 shallow freshwater lakes were investigated from May to September 2022. Eutrophication facilitated potential denitrification rate (Dt) without increasing nitrous oxide (N2O) production based on the significantly positive relationship between eutrophication and Dt. This should be attributed to the shift from incomplete (N2O producing process) to complete denitrification (N2 producing process). Compared to NarG mediating nitrate (NO3-) to nitrite (NO2-), fewer eutrophication indicators showed a positive relationship with NosZ mediating N2O to N2, suggesting that more stringent conditions are required for complete denitrification, which was achieved in the lakes we investigated. Optimal reduction in net carbon dioxide (CO2) emissions occurs at high levels of primary productivity, as indicated by the V-shaped relationship between chlorophyll a (Chl a) and CO2 emissions. However, in hyper-eutrophic lakes, there is an upward trend in CO2 production. The possible explanations should include CO2 production and fixation as well as methane (CH4) oxidation. The bell-shaped relationship between the net flux of CH4 emission and Chl a could be explained that CH4 was heavily oxidized due to sufficient oxygen caused by algal bloom. This fact gave evidence for the increase of the net flux of CO2 emission in high primary productivity lakes. Therefore, the relationship and mechanism between net GHGs emission flux and eutrophication remained complex and various.

Hydrological regimes and water quality variations in the Yangtze River basin from 1998 to 2018.

Understanding the long-term variations in basins that undergo large-scale hydroelectric projects is crucial for effective dam operation and watershed management. In this study, comprehensive analyses were conducted on a dataset spanning over 20 years (1998-2018) of hydrological regime and physicochemical parameters from the Yangtze River basin to evaluate the potential impacts of the Three Gorges Dam. Water level significantly increased from 128.75±58.18 m in 2002 to 136.78±55.05 m in 2005, and the mean flow velocity significantly decreased from 2004 to 2010. However, no significant change in the flow was observed in the basin. Meanwhile, remarkable fluctuations in physicochemical parameters, including dissolved oxygen, chemical oxygen demand, conductivity, hardness, and alkalinity, were mainly observed during impoundment (2003-2009). After that, the above parameters tended to stabilize, and some even returned to their original levels. The dam's retention effect significantly reduced the suspended solids (SS) in both up- and downstream, to only one-third of the pre-operation level. And total phosphorus and chemical oxygen demand also significantly decreased with the decline of SS. Particularly, ammonium also showed a significant downward trend, with the up- and downstream of the dam falling by 36.8 % and 26.1 %, respectively. However, the increasing total nitrogen (7.5 % and 20.0 % up- and downstream of the dam, respectively) still threatened the water quality of the basin, especially in the estuaries. Additionally, the significant decline in dissolved oxygen downstream (from 8.53±1.08 mg/L to 8.11±1.36 mg/L) also exacerbated the hypoxia in the Yangtze River estuary. The results demonstrated the long-term impact of the construction of the Three Gorges Dam on the environmental elements of the Yangtze River basin, which provides reference data and guidance for the construction of big dams in major rivers in the future.

Myeloperoxidase G463A polymorphism and lung cancer risk in Asians: a pooled analysis.

Myeloperoxidase (MPO) is an endogenous oxidant enzyme and can generate reactive oxygen species. The MPO G463A polymorphism influences MPO transcription levels and has been proposed to be associated with risk of lung cancer. To assess the effect of MPO G463A polymorphism on lung cancer risk in Asians, a pooled analysis of published case-control studies was performed. PubMed, Embase, China Biomedical Literature, and Wanfang Medicine databases were searched for eligible studies. The strength of the association between MPO G463A polymorphism and lung cancer risk was measured by odds ratio (OR) with 95 % confidence interval (95% CI). Finally, eight studies with a total of 1,679 lung cancer cases and 1,876 non-cancer controls were included. Overall, MPO G463A polymorphism was associated with decreased risk of lung cancer risk in Asians under two genetic models (OR AA vs. GG = 0.58, 95% CI 0.36-0.96, P = 0.033; OR AA vs. GG+AG = 0.60, 95% CI 0.37-0.98, P = 0.040). There was no obvious risk of publication bias in this meta-analysis. In conclusion, the pooled analysis suggests that MPO G463A polymorphism is associated with decreased risk of lung cancer risk in Asians.

Aberrant expression of microRNAs involved in epithelial-mesenchymal transition of HT-29 cell line.

Epithelial-mesenchymal transition (EMT) is an essential step for cancer metastasis. MicroRNAs (miRNAs) are small non-coding RNAs that regulate target-mRNAs post-transcriptionally. The expression and function of miRNAs in EMT of HT-29 colonic cells remain elusive. This study looks at expression of miRNAs in EMT and explores the effects of miRNAs on EMT in HT-29 cell line. HT-29 was treated with TGF ß to establish an EMT model, in which a collection of miRNAs was dynamically regulated by real-time PCR (qPCR) analysis. Among them, miR-21 and miR-27 were significantly upregulated, while miR-22, miR-26, miR-30, miR-181, miR-200b, miR-200c and miR-214 were markedly downregulated. MiRNA-inhibitors were used to knockdown miRNAs in HT-29 and EMT markers were determined by qPCR to monitor the effects of miRNAs on EMT process. Results showed that miR-22 could not alter the expression of EMT markers, while knockdown of miR-200b could significantly increase that of epithelial markers, N-cadherin, Vimentin, α-Sma and Twist1 and decrease that of mesenchymal marker, E-cadherin. Bioinformatic analysis and Western blot showed that ZEB1 was directly suppressed by miR-200b. In conclusion, miRNAs are dynamically regulated in TGF ß-induced EMT of HT-29 and miR-200b was essential for EMT by suppressing the expression of ZEB1 in HT-29.

Predominance of ammonia-oxidizing archaea and nirK-gene-bearing denitrifiers among ammonia-oxidizing and denitrifying populations in sediments of a large urban eutrophic lake (Lake Donghu).

The coupled nitrification-denitrification process plays a pivotal role in cycling and removal of nitrogen in aquatic ecosystems. In the present study, the communities of ammonia oxidizers and denitrifiers in the sediments of 2 basins (Guozhenghu Basin and Tuanhu Basin) of a large urban eutrophic lake (Lake Donghu) were determined using the ammonia monooxygenase subunit A (amoA) gene and the nitrite reductase gene. At all sites of this study, the archaeal amoA gene predominated over the bacterial amoA gene, whereas the functional gene for denitrification nirK gene far outnumbered the nirS gene. Spatially, compared with the Tuanhu Basin, the Guozhenghu Basin showed a significantly greater abundance of the archaeal amoA gene but less abundance of the nirK and nirS genes, while there was no significant difference of bacterial amoA gene copy numbers between the 2 basins. Unlike the archaeal amoA gene, the nirK gene showed a significant difference in community structure between the 2 basins. Archaeal amoA diversity was limited to the water-sediment cluster of Crenarchaeota, in sharp contrast with nirK for which 22 distinct operational taxonomic units were found. Accumulation of organic substances were found to be positively related to nirK and nirS gene copy numbers but negatively related to archaeal amoA gene copy numbers, whereas the abundance of the bacterial amoA gene was related to ammonia concentration.

Metabolites of extracellular organic matter from Microcystis and Dolichospermum drive distinct modes of carbon, nitrogen, and phosphorus recycling.

Algal extracellular organic matter (EOM) metabolites exert considerable impact on the carbon (C), nitrogen (N), and phosphorus (P) cycles mediated by attached bacteria. Field investigations were conducted in two ponds to explore the relationship among EOM metabolites from Microcystis and Dolichospermum, co-occurring microbes, and nutrient recycling from April 2021 to December 2021. Microcystis blooms primarily produced more complex bound EOM (bEOM) metabolites with many amino acid components, which facilitated bacterial colonization and provided sufficient substrates for ammonification. Meanwhile, high abundances of dissimilatory nitrate reduction to ammonium genes from co-occurring microbes such as Rhodobacter have demonstrated their strong N retention ability. Metabolic products of bEOM from Microcystis comprise a large number of organic acids that can solubilize non-bioavailable P. All these factors have collectively resulted in the increase of all fractions of N and P, except for nitrate (NO3--N) in the water column. In contrast, the EOM metabolite from Dolichospermum was simple, coupled with high abundance of functional genes of α-glucosidase, and produced small molecular substances fueling denitrification. The metabolic products of EOM from Dolichospermum include abundant N-containing substances dominated by heterocyclic substances, suggesting that the metabolic products of Dolichospermum are not conducive to N regeneration and retention. Therefore, the metabolic products of EOM from Microcystis triggered a shift in the attached microbial community and function toward C, N, and P recycling with close mutual coupling. Acquisition of N and P in Dolichospermum is dependent on itself based on N fixation and organic P hydrolysis capacity. This study provides a new understanding of the contribution of algal EOM to the nutrient cycle.

MicroRNAs are dynamically regulated and play an important role in LPS-induced lung injury.

Acute lung injury is characterized by an increase of inflammatory reaction and severe lung edema. Even if there have been great advances in the identification of genes and signaling pathways involved in acute lung injury, the fundamental mechanisms of initiation and propagation of acute lung injury have not been understood completely. A growing amount of evidence indicates that microRNAs (miRNAs) are involved in various human diseases. However, the expression profile and function of miRNAs in acute lung injury have not been investigated. Here, using real-time polymerase chain reaction analysis, we show that a collection of miRNAs is dynamically regulated in lipopolysaccharide (LPS)-induced mouse acute lung injury. Among them, miR-199a and miR-16 are the most significantly down-regulated miRNAs. To study the role of miR-199a and miR-16 in acute lung injury, an over-expression of miR-199a or miR-16 assay was performed in LPS-treated A549 cells, and then the expression of inflammatory factors was analyzed. Over-expression of miR-199a could not alter the expression level of interleukin (IL)-6 and tumor necrosis factor-alpha (TNFα), while up-regulation of miR-16 could significantly down-regulate IL-6 and TNFα expression level. Using bioinformatic analysis, we show that a 3' untranslational region (UTR) of IL-6 and TNFα contains the binding sites of miR-16. Accordingly, over-expression of miR-16 could significantly suppress the luciferase activity of reporter fusion with the binding sites of TNFα in its 3'UTR region, suggesting that miR-16 played its role in LPS-induced lung inflammation by a direct manner. In this study, we show for the first time that miRNAs are dynamically regulated and play an important function in LPS-induced lung injury.

Organic carbon quantity and composition jointly modulate the differentiation of nitrate reduction pathways in sediments of the Chinese eutrophic lake, Lake Chaohu.

Twelve sampling sites from two basins of Lake Chaohu were studied seasonally from June 2020 to April 2021 in Hefei City (China) to better understand the effect of organic carbon (C) quantity and composition on nitrate (NO3--N) reduction pathways. Serious algal bloom in the west basin of Lake Chaohu (WLC) resulted in higher organic C accumulation and NO3--N deficiency in interstitial water compared to the east basin of Lake Chaohu (ELC), jointly leading to a high C/NO3--N ratio. This triggered dissimilatory nitrate reduction to ammonium (DNRA) over denitrification in terms of higher DNRA rate, nitrogen retaining index (NRI), and nrfA gene abundance mediating DNRA. Furthermore, high oxygen-alkyl C and abundance of functional genes mediating labile organic C decomposition and DNRA suggested that the alkyl carbon-oxygen bond was responsible for DNRA induction. Different bacterial community composition and diversity involved in C and nitrogen (N) metabolism in two basins indicated that bacteria in sediments of WLC were more active in NO3--N reduction. Spearman correlation analysis showed that the less represented genera, such as Thiobacillus and Clostridium, were positively correlated with both organic C and NO3--N reduction rates, respectively. Hence, organic C composition could affect NO3--N reduction function by shaping the specific bacterial community.

The role of sulfur cycle and enzyme activity in dissimilatory nitrate reduction processes in heterotrophic sediments.

The dissimilatory nitrate (NO3-) reduction processes (DNRPs) play an important role in regulating the nitrogen (N) balance of aquatic ecosystem. Organic carbon (OC) and sulfur are important factors that influence the DNRPs. In this study, we investigated the effects of sulfur cycle and enzyme activity on DNRPs in the natural and human-modified heterotrophic sediments. Quarterly monitoring of anaerobic ammonium oxidation, denitrification (DNF), and dissimilatory NO3- reduction to ammonium (DNRA) in sediments was conducted using 15N isotope tracing method. qPCR and high-throughput sequencing were applied to characterize the DNF and DNRA microbial abundances and communities. Results showed that instead of the OC, the glucosidase activity (GLU) was the key driver of the DNRPs. Furthermore, instead of the ratio of OC to NO3-, the GLU and the ratio of OC to sulfide (C/S) correctly indicated the partitioning of DNRPs in this study. We deduced that the sulfur reduction processes competed with the DNRPs for the available OC. In addition, the inhibitory effect of sulfide (final product of the sulfur reduction processes) on the DNRPs bacterial community were observed, which suggested a general restrictive role of the sulfur cycle in the regulation and partitioning of the DNRPs in heterotrophic sediments.

Implementation of an mHealth App to Promote Engagement During HIV Care and Viral Load Suppression in Johannesburg, South Africa (iThemba Life): Pilot Technical Feasibility and Acceptability Study.

BACKGROUND: South Africa has the largest HIV treatment program worldwide. Retention in care and medication adherence remain problematic necessitating innovative solutions for improving HIV care. The increasing availability and use of mobile technology can support positive clinical outcomes for persons living with HIV. iThemba Life is a mobile health app designed with input from South African health professionals and patients, promoting engagement with HIV care through access to medical results. OBJECTIVE: This study aimed to test the feasibility and acceptability of receiving HIV viral load (VL) results through the app and compare the time to HIV VL result return for study participants before and after app use. METHODS: Using convenience sampling, adults having routine VL phlebotomy were recruited from 2 Johannesburg health facilities. After signed consent, the app was downloaded on their Android smartphones, phlebotomy was performed, and the sample barcode was scanned through their phone to link the sample and app. Participants received a notification of the result availability and logged into the app to view results, their explanation and recommended action. RESULTS: Overall, 750 people were screened to enroll 500 participants. Of 750, 113 (15.1%) failed eligibility screening. 21.5% (137/637) had smartphone technical limitations preventing enrollment. Results were released to 92.2% (461/500) of participants' phones. App technical issues and laboratory operational issues limited the number of released results. Approximately 78.1% (360/461) results were viewed in the app. Median time from notification of availability to result viewed being 15.5 hours (0.6; range 0-150 days). Turnaround time from phlebotomy to the result being received was 6 (range 1-167) days for users versus 56 days (range 10-430 days; P<.001) before app use. Overall, 4% (20/500) of participants received unsuppressed results (VL>1000 copies/mL). Turnaround time for unsuppressed results was 7 days for participants versus 37.5 days before app use (P<.001). The difference before and after app use in the suppressed and unsuppressed users for time from sample collection to result delivery was statistically significant. Of 20 participants, 12 (60%) returned for a confirmatory VL during the study period. The time from an unsuppressed VL to a confirmatory VL was 106 days for app users versus 203 days before app use (P<.001). Overall, 52.4% (262/500) of participants completed an exit survey; 23.2% (58/250) reported challenges in viewing their VL results. Moreover, 58% (35/60) reported that they overcame challenges with technical assistance from others, and 97.3% (255/262) wanted to continue using the app for VL results. CONCLUSIONS: Using iThemba Life for VL results was well-received despite limited smartphone access for some participants. App users received results 10 times sooner than before the app and 5 times sooner if their VL >1000 copies/mL. This increased notification speed led to participants wanting to continue using iThemba Life.