Sulfonamide antibiotics (SAs), extensively utilized in the breeding industry, pharmaceutical industries, and human healthcare, enter the environment through wastewater discharge and surface runoff. Currently, SAs are widely detected across various environmental compartments, including water bodies (up to 17,400 ng/L), soils, and sediments (up to 2089 ng/g). The environmental persistence and potential ecological risks of SAs have attracted considerable attention. This review systematically summarizes the environmental occurrence, migration, and transformation behaviors of 12 representative SAs. Results show that the environmental transport of SAs is influenced by complex matrices and modulated by extreme environmental events, while their transformation is co-regulated by coupled physicochemical and biological processes. SAs can induce oxidative stress (e.g., EC50 for green algae reaching 5.53 mg/L), reproductive inhibition, and metabolic disorders in organisms, and may accumulate through the food chain (e.g., bioconcentration factor in shrimp as high as 5126 L/kg), thus posing threats to ecosystems and human health. Furthermore, environmental residues of SAs also promote the spread and horizontal transfer of antibiotic resistance genes (ARGs, e.g., sul1 and sul2 detected in 100

AIMS:This study aimed to isolate an algicidal bacterium able to strongly inhibit Microcystis growth and microcystins (MCs) production/release simultaneously, and to consolidate bacterial efficacy for potential practice. METHODS AND RESULTS:Algicidal bacterium Aeromonas sp. N3 effectively inhibited growth of 105 [non-quorum sensing (QS)-activated] and 108 cells/mL (QS-activated) Microcystis by 98.95% and 90.22% by day 26, respectively, and sharply decreased extracellular and intracellular MCs by > 90% for both densities, as detected by enzyme-linked immunosorbent assay. Quantitative polymerase chain reaction revealed algicidal effects involved stably strong downregulation of algal energy acquisition, nutrient assimilation, DNA repair, and heat-shock response. N3 exerted algicidal effect via excreted algicidal compounds, as its primary filtrates also stably suppressed Microcystis growth and MC-production/release with inferior efficacy than free-living N3, while its secondary filtrate with pre-exposure to Microcystis showed weaker efficacy. To consolidate N3's application potential, its immobilized agent was optimally constructed by dropping procedures with orthogonal tests using various polyvinyl alcohol-sodium alginate ratios. Alike to free-living N3, immobilized agent with equivalent cell loading posed equally strong inhibitory effects on Microcystis growth (> 90% inhibition) and extracellular/intracellular MCs content (> 95% inhibition), thus diminishing MC-pollution by blocking MC-synthesis/release, which is superior to by degrading aqueous MCs after release. CONCLUSIONS:Aeromonas sp. N3 had functional robustness and stability against Microcystis growth and MC-pollution, regardless of Microcystis density, exhibiting robust potential for mitigating both low- and high-density toxic Microcystis-dominated cyanobacterial blooms (corresponding to early- and mature-stage MCBs). Optimal construction of immobilized agent further consolidated its applicability in effective MCBs and MC-pollution mitigation.

Microcystins (MCs), the potent hepatotoxins produced by toxic strains of Microcystis and other cyanobacteria, pose a major threat to freshwater ecosystems worldwide. However, the regulatory mechanisms, evolutionary origin, and maintenance of this energy-intensive toxigenicity remain largely unresolved. Based on 132 non-redundant Microcystis strains, this study combined pan-genomics analysis, phylogenetic reconstruction, pan-genome-wide association analysis and machine learning approaches to investigate the regulatory and evolutionary basis of MCs production. Results suggest that MCs production likely originated as an ancestral trait in Microcystis, while secondary horizontal gene transfer (HGT) and homologous recombination across the MCs biosynthesis-related (mcy) gene cluster and its flanking regions might have contributed to its distribution among polyphyletic lineages. Enrichment analysis further indicated distinct metabolic strategies between toxic and non-toxic Microcystis strains. Toxic strains are enriched in secondary metabolism, whereas non-toxic strains prioritize core metabolic pathways. Through co-occurrence analysis and multi-method screening, this study identified a candidate type II toxin-antitoxin (TA) system (TumE-TumA) that may be synergistically associated with mcy gene cluster. Structural and energetic analyses predicted a potential interaction between the TumE-family toxin protein and mcyA RNA (ΔiG= -44.6 kcal/mol), suggesting its potential regulatory role in MCs biosynthesis. Taken together, these findings support a proposed co-evolutionary framework in which secondary HGT may contribute to the phylogenetic distribution of mcy gene cluster, while the TA system may form a synergistic network with mcy gene cluster, contributing to the maintenance and evolution of MCs production by balancing metabolic costs with ecological benefits. While these in silico predictions require experimental validation, they provide new insights into the adaptive evolution of cyanobacterial toxigenicity and inform future strategies for managing harmful algal blooms.

Phycoerythrin (PE) is a high-value fluorescent pigment-protein with broad applications in food, diagnostics, and therapeutics, yet its conventional production from marine algae faces challenges of unstable yield, high cost, and ecological concerns. This narrative review systematically evaluates the potential of freshwater microalgae as sustainable platforms for PE production within a circular economy framework. A structured literature search was conducted across Web of Science and Google Scholar using keywords related to freshwater algae, PE biosynthesis, genetic engineering, wastewater bioremediation, and biorefinery. Key findings demonstrate that specific Cyanobacteria and Cryptophyta strains (e.g., Anabaena fertilissima: 475 mg/g dry weight; Cryptomonas pyrenoidifera: 345 mg/g dry weight) exhibit yields comparable or superior to those of traditional marine sources. Genetic engineering strategies—including promoter engineering (e.g., psbA modification increasing expression 3.7-fold), heterologous expression (achieving 96.7% chromophorylation), and CRISPR-Cas9-mediated metabolic flux redirection—offer robust tools for enhancing PE yield and stability. Wastewater cultivation enables efficient removal of nutrients (>90% N/P) and emerging contaminants (e.g., >95% heavy metals, 50% pharmaceuticals, >84% microplastics) alongside biomass production. High-value PE applications—as fluorescent probes (quantum yield 0.98), photosensitizers in photodynamic therapy, and photocatalysts for pollutant degradation (>90% removal)—provide economic drivers. A SWOT-TOWS analysis identifies strategic pathways addressing cost, scalability, and regulatory barriers. We propose an integrated biorefinery model coupling wastewater treatment, multi-product cascading (PE, lipids, biochar, biofertilizers), and policy instruments (carbon credits, purity standards) to accelerate sustainable commercialization of freshwater algae-derived PE.

Widespread distribution of per- and polyfluoroalkyl substances (PFAS) arouses ongoing concern on their eco-risks. As crucial aquatic primary producers, diverse microalgae inevitably coexist with PFAS contamination, understanding PFAS impact on microalgae is vital for eco-risks assessment/control. However, multiple features including PFAS structural heterogeneity and microalgal characteristics severely impact eco-risk assessment. Disentangling non-linear microalgal responses to key features and feature interaction, and microalgal species-dependent effects of complex molecular microstructures remains challenging. This study integrated interpretable and causal machine-learning approaches to optimize a modeling framework for interpreting PFAS toxicity to microalgae. Optuna-optimized CatBoost model with 7-fold cross-validation achieved robust performance in predicting microalgal activity at PFAS exposure. PFAS concentration, exposure time duration, chain length, microalgal species and initial cell density were identified as key features governing microalgal activity, with a model-derived aggregated response transition around the 10⁴ µg/L concentration range and an intensified inhibitory pattern beyond C7 chain length. The stronger contribution of exposure features, especially PFAS concentration, indicated that the model is effective in capturing microalgal response pattern across heterogeneous exposure scenarios, while PFAS-related structural features still provided crucial information for interpreting PFAS structural effects. Feature interaction analysis verified that PFAS concentration and chain length exhibited synergistic inhibitory effects, whereas initial cell density provided antagonistic buffering capacity. Moreover, X-Learner-based causal inference revealed divergent effects of PFAS chain length, sulfonate group, ether bond and saturated fluorotelomer on different microalgal species, and proposed a conceptual interpretation termed "bio-interface structure-molecular conformation matching": rigid long-chain PFAS may interact more strongly with EPS-rich microalgal species, sulfonate-containing PFAS may encounter algaenan-related resistance in Chlorophyceae-belonging green algae, while saturated fluorotelomers may show greater conformational adaptability toward loose-cell-wall diatom via "flexible hinge" effect, whereas ether bond-containing PFAS is more likely to experience interfacial retention within irregularly porous rough surface of Scenedesmus obliquus. This study facilitates PFAS eco-risk assessment and provides novel interpretive insights into PFAS-microalgae interactions across heterogeneous exposure scenarios.

Microcystis aeruginosa as prevalent bloom-forming cyanobacterium deteriorates water quality and excretes microcystins (MCs) to pose notable eco-risk. Allelochemicals are promising algicides, yet inconsistent research settings (allelochemical concentration, type, action time, action mode) lead to debates on their impacts on M. aeruginosa growth and MC-pollution. By integrating 2124 data points from 121 articles, this study proposed multifactor meta-analysis approach integrating univariate subgroup with multifactor interaction analyses, which fundamentally differs from conventional approaches and enables simultaneous quantification of multiple contextual outcomes to quantitatively assess context-dependent allelochemical effects on M. aeruginosa growth, physiology and MC-production/release, and confer mechanistic insights. Results revealed that allelochemicals inhibit M. aeruginosa growth with overall effect size of -1.24 (inhibitory effect), and high-level heterogeneity among articles reflected context-dependence of allelochemical effect. Ultrahigh concentration (>100 mg/L) and long action time (10-15 days) were verified to most strongly inhibit M. aeruginosa growth and MC-release. Higher concentrations and longer time further disrupted photosynthesis, antioxidant activation and MC-production and -release, thus intensifying growth inhibition. Compared to single-time addition, sustained continuous addition/release more effectively inhibited M. aeruginosa growth by more strongly suppressing antioxidant activation, photosynthesis and MC-production and release. Among allelochemical types, terpenoids compounds exert the strongest growth-inhibition without decreased MC-release, and phenolic compounds decreased MC-production/release when inhibiting growth, acting as safe algicides. Yet, nitrogen-containing and aliphatic compounds moderately restrained growth but slightly boosted MC-release, raising secondary pollution risks. Allelochemical concentration and action time jointly induced distinct nonlinear growth response across allelochemical types, with significant concentration-time nonlinearity observed for phenolic, aliphatic and terpenoids compounds, and exerted divergent nonlinear effects on MC-pollution dynamics: MC-production responded nonlinearly to phenolic and aliphatic compounds, while terpenoids caused no significant nonlinear variation in either MC-production or MC-release. This study provided novel insights for selectively coordinating allelochemical parameters for efficient M. aeruginosa blooms and MC-pollution control, which offered solid application support.

Water scarcity poses rigorous challenges to socio-economic development, necessitating more efficient options for water and resource management [...]

The global expansion of Microcystis-dominated cyanobacterial blooms (MCBs) threatens aquatic ecosystems health, where Microcystis population comprises coexisting microcystin (MC)-producing (MC+) and MC-free (MC-) strains. Luteolin, an allelopathic algicide, has shown potential in inhibiting MC+Microcystis growth and MC-production/-release. This study investigated luteolin's effects on co-cultured MC+ and MC-Microcystis (i.e. Microcystis population), aiming to compare their sensitivity and elucidate mechanisms via MC-production/-release, proteomics, and metabolomics. Results showed that luteolin inhibited Microcystis population growth by 41.10%-58.37%, with MC+ strain exhibiting greater sensitivity, as indicated by stronger growth inhibition ratio (30.43%-62.61%) and more severe cellular damage for MC+ strain. Integrated proteomic and metabolomic analyses further revealed the underlying mechanisms of such sensitivity difference: MC+Microcystis exhibited severe impairments in photosynthetic activity, cell membrane composition, and antioxidant systems, alongside disruptions in protein biosynthesis, nucleotide degradation, and hindered DNA replication and repair. In contrast, MC-Microcystis experienced similar but milder disturbances, while promptly initiating compensatory responses. It enhanced carbohydrate metabolism and ATP synthase activity, promoted DNA replication and protein biosynthesis, and activated inflammatory responses to counteract luteolin stress. Additionally, although luteolin significantly decreased MC levels in the aqueous phase to 14.04 μg/L, luteolin increased MCs synthesis and conversation within co-cultured MC+Microcystis cells, potentially exacerbating eco-risks due to prolonged MC-release. This study clarifies the differential sensitivity of MC+ and MC-Microcystis to allelopathic algicide and their molecular mechanisms, offering insights for developing targeted management plans, based on each strain's survival strategies, to control MCBs.

Global increase in Microcystis-dominated cyanobacterial blooms (MCBs) severely threatens ecological and human health. Intraspecific interaction between microcystin (MC)-producing (MC+) Microcystis and co-existing MC-free (MC-) Microcystis influences the relative abundance of MC+Microcystis, ultimately determining the toxicity and hazard of MCBs. However, specific allelochemicals driving this interaction and underlying molecular mechanisms remain unclear. This study confirmed that intraspecific interaction promoted the competitive advantage of MC+Microcystis over MC-Microcystis and unveiled the joint intracellular and extracellular regulatory strategies of MC+Microcystis based on proteomics-metabolomics analyses and biochemical validation. Intracellularly, MC+Microcystis enhanced pentose phosphate pathway and lipid and fatty acid biosynthesis to maintain cellular functions and membrane stability, but inhibited glycolysis, tricarboxylic acid cycle, and protein biosynthesis to optimize energy utilization for growth and proliferation. Extracellularly, MC+Microcystis released allelochemicals, including cytidine diphosphate-diacylglycerol and N-acyl-homoserine lactones, to inhibit MC-Microcystis growth by 13.53% and 16.39%, respectively, thereby achieving its competitive advantage. In contrast, MC-Microcystis exhibited the suppressed photosynthesis and oxidative phosphorylation, imbalanced anti-inflammatory responses, nucleic acid degradation, and membrane damage, resulting in its competitive disadvantage in co-culture. These findings provide new insights into the competitive dynamics between MC+ and MC-Microcystis, and their involved implications for aquatic ecosystem health.

Paddy soil plays a crucial role in terrestrial carbon turnover and climate change. The effects of the continuous application of various fertilisers on soil organic carbon (SOC) accumulation and stabilisation across the paddy soil profile remain inadequately understood. This study systematically compared the impact of four consecutiveyear application of kitchen waste fertiliser (KWF), chicken manure fertiliser (CMF) and conventional inorganic fertiliser (CF) on total carbon stock and SOC composition at surface (0-20 cm), subsurface (20-40 cm) and deep (40-60 cm) layers of paddy soil in the Yangtze River Delta, China. KWF enhanced surface SOC and soil inorganic carbon (SIC) by 25 % and 19 %, respectively, outperforming other fertilisers in surface SOC and SIC accumulation. KWF also increased SIC throughout the soil profile, thereby substantially improving soil fertility and carbon stock. Both organic fertilisers raised the proportion of particulate organic carbon (POC) but reduced the proportion of mineral-associated organic carbon (MAOC) at the surface layer, while increasing MAOC content at the surface layer, with the most significant increase observed in KWF treatment. Unlike CMF and CF, KWF induced a marked dominance of microbial-derived carbon in MAOC and in SOC (i.e. MAOC + POC) across the soil profile by more effectively increasing bacterial necromass carbon (BNC), which constituted 72 %, 98 % and 99 % of microbial-derived carbon in MAOC at the surface, subsurface and deep layer, respectively. Furthermore, KWF increased the MAOC proportion and caused microbial-derived carbon (primarily consisting of BNC) to dominate in MAOC and in SOC (i.e. MAOC + POC) at the deep layer, thus facilitating deep-layer SOC stability despite no significant increase in deep-layer SOC content. These findings underscore the unique potential of KWF as a carbon-sequestering fertiliser for SOC accumulation and stabilisation across the paddy soil profile, by enriching recalcitrant microbial-derived carbon in MAOC and SOC, primarily through bacterial turnover pathways. This study has significant implications for optimising fertilisation practices for carbon sequestration to enhance paddy soil fertility and mitigate climate warming in urbanising regions.

Owing to the huge amounts and perishable character of vegetable wastes, composting is one of the best options for recycling vegetable wastes post-harvest. The initial moisture content (MC) is critical for optimizing composting process, but the effect of high MC in undehydrated vegetable wastes on composting was rarely reported. For this, the plant-scale windrows were prepared by mixing cauliflower waste and maize straw at different ratios to control initial MC of 70 % (T1-70) and 80 % (T2-80), respectively, and composted in winter. As composting progressed, substantial organic matter degradation, progressive humification, decreases in electrical conductivity and increases of pH and germination index (GI) were observed in both treatments. Nonetheless, T1-70 accelerated heating rate early during composting, prolonged high temperature period (>50 °C) by 30 d, thus increased the harmless level of composting, and significantly improved the humification of end-products compared to T2-80. Results also revealed that T1-70 activated more indigenous microbes and enhanced microbial interactions early during composting, with the fungi enriched in T1-70 playing an important role in accelerating the composting process. Remarkably, the difference in composting temperatures, humification degree, and microbial communities between the two treatments was most significant during the maturation phase. In this phase, MWH_CFBk5, Planktosalinus, Pseudopedobacter, and Luteimonas enriched in T1-70 were positively correlated with humification indices. It is suggested that the effect of initial MC, resulting from different ratios of vegetable waste to maize straw, on their composting was mediated by the composting temperature and microbial communities at low temperatures.

Luteolin has shown great potential in inhibiting Microcystis-dominated cyanobacterial blooms. However, widespread microplastics (MPs) in natural aquatic systems often serve as substrates for cyanobacterial growth, which could impact cyanobacterial resistance to external stresses and interfere with luteolin's algicidal effect. This study explored the influence of virgin and diversely-aged polystyrene microplastics (PS-MPs) on inhibitory effect of luteolin on Microcystis growth and its microcystins (MCs) production/release. Moreover, the underlying mechanisms were also revealed by jointly analyzing SEM image, antioxidant response, exopolymeric substances (EPSs) production, and functional gene expression. Results suggested that 0.5, 5, and 50 mg/L virgin and diversely-aged PS-MPs almost weakened growth inhibition and oxidative damage of two doses of luteolin against Microcystisby stimulating its EPSs production and inducing self-aggregation of Microcystis cells and/or heteroaggregation between Microcystis cells and PS-MPs. Compared to virgin PS-MPs, photo-aged PS-MPs possessed rougher flaky surfaces, and hydrothermal-aged PS-MPs showed internal cracking. These characteristics led to greater stimulation of EPS production and exhibited more significant protective effects on Microcystis. Notably, PS-MPs also decreased MCs content in aqueous phase, likely because they adsorbed some MCs. Such toxigenic hetero-aggregates formed by MCs, MPs, and Microcystis cells would directly poison grazing organisms that consume them and create more pathways for MCs into food web, posing greater eco-risks. This is the first study to clarify the influence and mechanisms of virgin and diversely-aged MPs on allelopathic algicidal effects from the perspective of microalgal inherent adaptive strategies.

This study aimed to explore natural aging effect of distiller’s grain-derived biochar (DGB) at various amendment rates (2%, 4%, w/w) on wheat ( Triticum aestivum L.) growth, development and Cd uptake in soil, and provide novel insights in effect mechanisms from views of soil Cd fractions and rhizospheric microbiota. Results showed that DGB amendment promoted wheat growth. Rising DGB rate progressively increased soil pH, soil organic matter (SOM), total carbon (TC), total nitrogen (TN), NH 4 -N, available K, and residual Cd content to more greatly promote chlorophyll content and decrease Cd uptake of wheat. With 6-month aging, soil TN, available K and residual Cd content continuously increased to decline Cd bioavailability, which further restricted Cd uptake by wheat roots, stems, and leaves, and did not obviously change Cd uptake by wheat grains. Contrarily, soil NO 3 -N content progressively decreased with rising DGB rate and aging, partly due to progressively decreased nitrifier abundances of Nitrosomonadaceae and Nitrospiraceae with rising DGB rate and aging, according to rhizospheric bacterial composition. Statistical analysis verified that DGB rate and aging were synergistic factors to jointly involve soil nutrient increase and Cd fractions re-distribution. Rising DGB rate and aging jointly increased the abundances of Actinobacteria, Cyanobacteria, and Fibrobacteria phyla, and Lysobacter , Massilia , Pseudarthrobacter , and Iamia genera that positively correlated to soil residual Cd, TN, SOM, TC, and available K content, suggesting that such bacterial groups also drove soil fertility improvement and Cd bioavailability decrease. Consequently, amending 4% DGB with aging was proposed as appropriate for improving soil fertility and blocking Cd-induced health risk.

Micro/nano-plastics (MNPs), as emerging persistent pollutants, are threatening freshwater ecosystems worldwide. Microalgae are important primary producers at the base of trophic level and susceptible to MNPs contamination, possibly resulting in further contamination in higher trophic levels and water quality. This study conducted a systematic review of 1071 observations from 63 publications, utilizing meta-analysis and subgroup analysis to investigate the toxicological effect patterns of MNPs parameters (size, concentration, and type) on microalgae. We also explored the potential eco-risks of certain specific MNPs parameters and subtle variations in the response of various microalgae taxa to MNPs. Results suggested that microplastics significantly inhibited microalgal photosynthesis, while nano-plastics induced more severe cell membrane damage and promoted toxin-release. Within a certain range of concentrations (0∼50 mg/L), rising MNPs concentration progressively inhibited microalgal growth and chlorophyll-a content, and progressively enhanced toxin-release. Among MNPs types, polyamide caused higher growth inhibition and more severe lipid peroxidation, and polystyrene induced more toxin-release, whereas polyethylene terephthalate and polymethyl methacrylate posed minimal effects on microalgae. Moreover, Bacillariophyta growth was inhibited most significantly, while Chlorophyta displayed strong tolerance and Cyanophyta possessed strong adaptive and exceptional resilience. Particularly, Komvophoron, Microcystis, Nostoc, Scenedesmus, and Gomphonema were more tolerant and might dominate freshwater microalgal communities under MNPs contamination. These results are crucial for acquiring the fate of freshwater microalgae under various MNPs contamination, identifying dominant microalgae, and reasonably assessing and managing involved eco-risks.

Microcystis-dominated cyanobacterial blooms (MCBs) frequently occur in freshwaters worldwide due to massive Microcystis colony formation and severely threaten human and ecosystem health. Quorum sensing (QS) is a direct cause of Microcystis colony formation that drives MCBs outbreak by regulating Microcystis population characteristics and behaviors. Many novel findings regarding the fundamental knowledge of the Microcystis QS phenomenon and the signaling molecules have been documented. However, little effort has been devoted to comprehensively summarizing and discussing the research progress and exploration directions of QS signaling molecules-mediated QS system in Microcystis. This review summarizes the action process of N-acyl homoserine lactones (AHLs) as major signaling molecules in Microcystis and discusses the detailed roles of AHL-mediated QS system in cellular morphology, physiological adaptability, and cell aggregation for colony formation to strengthen ecological adaptability and competitive advantage of Microcystis. The research progress on QS mechanisms in Microcystis are also summarized. Compared to other QS systems, the LuxI/LuxR-type QS system is more likely to be found in Microcystis. Also, we introduce quorum quenching (QQ), a QS-blocking process in Microcystis, to emphasize its potential as QS inhibitors in MCBs control. Finally, in response to the research deficiencies and gaps in Microcystis QS, we propose several future research directions in this field. This review deepens the understanding on Microcystis QS knowledge and provide theoretical guidance in developing strategies to monitor, control, and harness MCBs.

Converting distillers’ grains (DGs) into biochar (BC) is sustainable option for waste-recycling, but how different aging times and application rates DG-derived BC (DG-BC) influenced lettuce growth and cadmium (Cd) uptake in soil was unclear. This study explored DG-BC rate- and aging time-dependent effect on lettuce growth and Cd uptake, and effect mechanisms from insights of soil nutrient and Cd bioavailability, lettuce metabolic activity and rhizospheric bacterial composition. Pot experiments involved three DG-BC rates (1

Luteolin continuous-release microsphere (CRM) has promising algicidal effect against Microcystis, but how nitrogen (N) level impacted CRM effects on Microcystis growth and microcystins (MCs) pollution was never tracked along long term. This study revealed that luteolin CRM exerted long-term and robust inhibitory effects on Microcystis growth and MC-pollution by sharply decreasing extracellular and total MCs content at each N level, with growth inhibition ratio of 88.18%–96.03%, 92.91%–97.17% and 91.36%–95.55% at 0.5, 5 and 50 mg/L N, respectively, during day 8–30. Further analyses revealed that CRM-stress inhibited transferase, GTPase and ATPase activities, ATP binding, metal ion binding, fatty acid biosynthesis, transmembrane transport and disrupted redox homeostasis to pose equally robust algicidal effect at each N level. At lower N level, CRM-stress tended to induce cellular metabolic mode towards stronger energy supply/acquisition but weaker energy production/consumption, while triggered a shift towards stronger energy production/storage but weaker energy acquisition/consumption as N level elevated, thus disturbing metabolic balance and strongly inhibiting Microcystis growth at each N level. Long-term robust algicidal effect of CRM against other common cyanobacteria besides Microcystis was evident in natural water. This study shed novel insights into inhibitory effects and mechanisms of luteolin CRM on Microcystis growth and MC-pollution in different N-level waters.

Microcystin (MC)-producing (MC+) and MC-free (MC-) Microcystis always co-exist and interact during Microcystis-dominated cyanobacterial blooms (MCBs), where MC+Microcystis abundance and extracellular MC-content (EMC) determine the hazard extent of MCBs. The current study elucidated intraspecific interaction between MC+ and MC-Microcystis at various nitrogen (N) levels (0.5-50 mg/L) and how such N-mediated interaction impacted algicidal and EMC-inhibiting effect of luteolin, a natural bioalgicide. Conclusively, MC+ and MC-Microcystis were inhibited mutually at N-limitation (0.5 mg/L), which enhanced the algicidal and EMC-inhibiting effects of luteolin. However, at N-sufficiency (5-50 mg/L), MC-Microcystis promoted MC+ ecotype growth and dominance, and such intraspecific interaction induced the cooperative defense of two ecotypes, weakening luteolin's algicidal and EMC-inhibiting effects. Mechanism analyses further revealed that MC+Microcystis in luteolin-stress co-culture secreted exopolymeric substances (EPSs) for self-protection against luteolin-stress and also released more EMC to induce EPS-production by MC-Microcystis as protectants, thus enhancing their luteolin-resistance and promoting their growth. This study provided novel ecological implications of MC-Microcystis toward MC+ ecotype in terms of assisting the dominant establishment of MC+Microcystis and cooperative defense with MC+ ecotype against luteolin, which guided the application of bioalgicide (i.e. luteolin) for MCBs and MCs pollution mitigation in different eutrophication-degree waters. This study contributes to the understanding of the intraspecific competition among Microcystis and guides the application of luteolin, a bioalgicide, in mitigating MCBs and MCs pollution in different eutrophication-degree waters.

Luteolin as a phytogenic algicide can inhibit the growth and microcystins (MCs) release of Microcystis, a dominant genus during cyanobacterial blooms, but how phosphorus (P) level impacts luteolin effect on its growth and MC-pollution risk is unclear. By employing Microcystis aeruginosa as test alga, this study addressed this concern and explored response mechanisms from novel insights of relationship between extracellular polysaccharide (ex-poly) and protein (ex-pro) contents and MC-production/release. At each P level (0.05-5 mg/L), rising luteolin dose more greatly inhibited Microcystis growth and MC-pollution risk, with growth inhibition ratio of around 10%-30%, 20%-50% and 40%-90% for 3, 6 and 12 mg/L luteolin, respectively, but almost increasingly enhanced cellular ability of MC-production/conservation and total and bound ex-poly/ex-pro production. Rising P level promoted Microcystis growth and intracellular/extracellular MCs content (IMC, EMC) in test system at each luteolin dose, thus higher P level weakened algicidal and MC-removal effects of luteolin, indicating that P-decrease was required for stronger application outcome of luteolin. Total and bound ex-poly/ex-pro amount were positively correlated with cellular MC-production/conservation ability, IMC and EMC, which constituted cooperative stress-defense of Microcystis at each P level. Besides, rising luteolin dose posed stronger algicidal effect by inactivating gene expression involving peroxidase synthesis (especially at P-limitation), photosynthesis and P acquisition, while rising P level alleviated algicidal and MC-pollution inhibition effects of luteolin by enhancing gene expression involving N acquisition and peroxidase synthesis. This study shed novel insights for P-dependent effect and mechanisms of luteolin on toxigenic Microcystis growth and MC-pollution control, which guided to mitigating toxigenic Microcystis-dominated cyanobacterial blooms in different P-level water areas.

Brevibacillus laterosporus ZR-11, a bio-control strain, was innovatively inoculated at maturity stage of composting to clarify its effect on physicochemical parameters and indigenous bacterial community structure in compost pile. Results revealed that ZR-11 inoculum rapidly increased pile temperature to 52 ºC and raised germination index (GI) value to beyond 85% on day 3, thereby achieving higher pile temperature and GI in the inoculated group than the non-inoculated group almost along maturity stage, and also decreased C/N ratio of the inoculated group to below 20 by composting end (day 8). Also, ZR-11 succeeded in colonizing compost pile along maturity stage. These suggested that ZR-11 as inoculum at maturity stage could accelerate compost maturation and have a potential to participate in bio-fertilizer production. High-throughput sequencing indicated that bacterial community structure experienced substantial succession in the inoculated and non-inoculated groups, and Firmicutes, Proteobacteria, and Actinobacteria were the dominant phyla in the two groups during maturity stage, with their abundances higher in the inoculated group. Saccharomonospora and Ammoniibacillus abundance increased on day 3 while Actinomadura abundance increased on day 6 in the inoculated group. As verified statistically, pile temperature and pH were key factors closely linked to dominant genera abundance, where Saccharomonospora and Ammoniibacillus abundance were positively correlated to pile temperature, while Actinomadura abundance was positively correlated to pile pH. Thus, it was inferred that ZR-11 inoculum could improve parameters such as temperature and pH to modify dominant genera abundance, thus regulating indigenous bacterial community succession, which might in turn promote compost maturation.