Search

Background and aims: Phosphate-solubilizing bacteria (PSB) possess significant potential for enhancing soil phosphorus bioavailability, but their efficacy may be constrained by carbon and nitrogen availability. Algae exhibit synergistic interactions with bacteria through producing active organic carbon. However, the influence of algae and PSB together on phosphorus bioavailability under varying nitrogen levels remains unclear.We conducted a microcosm experiment to explore the effects of applying Chlorella-Bacillus biofertilizer, along with various nitrate addition amounts, on both soil microbial community composition and phosphorus bioavailability. In addition, we employed a co-culture of Chlorella and Bacillus with different nitrogen concentrations to investigate the possible effects of nitrate addition on the production of organic anions and phosphatases of the Chlorella-Bacillus communities by using metabolomic analysis.Chlorella-Bacillus biofertilizer significantly increased soil Olsen-P concentration via strong interactive effects correlating with the various nitrate addition amounts in the microcosm experiment. These effects were due mainly to reducing the algal diversity, soil pH, and changing dissolved organic matter (DOM) characteristics, especially increasing the humification index (HIX). The metabolomic analyses of co-culture confirm that pathways related to the biosynthesis of fatty acids and phosphatases production are enhanced when nitrogen levels are high.Chlorella-Bacillus biofertilizer has significantly interactive effects with nitrate addition on soil phosphorus bioavailability by influencing soil DOM, pH and production of organic anions and phosphatases. These insights are useful for optimizing bio-fertilizer-nitrate combinations for increasing phosphorus bioavailability thereby reducing chemical fertilizer requirements.Methods: Phosphate-solubilizing bacteria (PSB) possess significant potential for enhancing soil phosphorus bioavailability, but their efficacy may be constrained by carbon and nitrogen availability. Algae exhibit synergistic interactions with bacteria through producing active organic carbon. However, the influence of algae and PSB together on phosphorus bioavailability under varying nitrogen levels remains unclear.We conducted a microcosm experiment to explore the effects of applying Chlorella-Bacillus biofertilizer, along with various nitrate addition amounts, on both soil microbial community composition and phosphorus bioavailability. In addition, we employed a co-culture of Chlorella and Bacillus with different nitrogen concentrations to investigate the possible effects of nitrate addition on the production of organic anions and phosphatases of the Chlorella-Bacillus communities by using metabolomic analysis.Chlorella-Bacillus biofertilizer significantly increased soil Olsen-P concentration via strong interactive effects correlating with the various nitrate addition amounts in the microcosm experiment. These effects were due mainly to reducing the algal diversity, soil pH, and changing dissolved organic matter (DOM) characteristics, especially increasing the humification index (HIX). The metabolomic analyses of co-culture confirm that pathways related to the biosynthesis of fatty acids and phosphatases production are enhanced when nitrogen levels are high.Chlorella-Bacillus biofertilizer has significantly interactive effects with nitrate addition on soil phosphorus bioavailability by influencing soil DOM, pH and production of organic anions and phosphatases. These insights are useful for optimizing bio-fertilizer-nitrate combinations for increasing phosphorus bioavailability thereby reducing chemical fertilizer requirements.Results: Phosphate-solubilizing bacteria (PSB) possess significant potential for enhancing soil phosphorus bioavailability, but their efficacy may be constrained by carbon and nitrogen availability. Algae exhibit synergistic interactions with bacteria through producing active organic carbon. However, the influence of algae and PSB together on phosphorus bioavailability under varying nitrogen levels remains unclear.We conducted a microcosm experiment to explore the effects of applying Chlorella-Bacillus biofertilizer, along with various nitrate addition amounts, on both soil microbial community composition and phosphorus bioavailability. In addition, we employed a co-culture of Chlorella and Bacillus with different nitrogen concentrations to investigate the possible effects of nitrate addition on the production of organic anions and phosphatases of the Chlorella-Bacillus communities by using metabolomic analysis.Chlorella-Bacillus biofertilizer significantly increased soil Olsen-P concentration via strong interactive effects correlating with the various nitrate addition amounts in the microcosm experiment. These effects were due mainly to reducing the algal diversity, soil pH, and changing dissolved organic matter (DOM) characteristics, especially increasing the humification index (HIX). The metabolomic analyses of co-culture confirm that pathways related to the biosynthesis of fatty acids and phosphatases production are enhanced when nitrogen levels are high.Chlorella-Bacillus biofertilizer has significantly interactive effects with nitrate addition on soil phosphorus bioavailability by influencing soil DOM, pH and production of organic anions and phosphatases. These insights are useful for optimizing bio-fertilizer-nitrate combinations for increasing phosphorus bioavailability thereby reducing chemical fertilizer requirements.Conclusion: Phosphate-solubilizing bacteria (PSB) possess significant potential for enhancing soil phosphorus bioavailability, but their efficacy may be constrained by carbon and nitrogen availability. Algae exhibit synergistic interactions with bacteria through producing active organic carbon. However, the influence of algae and PSB together on phosphorus bioavailability under varying nitrogen levels remains unclear.We conducted a microcosm experiment to explore the effects of applying Chlorella-Bacillus biofertilizer, along with various nitrate addition amounts, on both soil microbial community composition and phosphorus bioavailability. In addition, we employed a co-culture of Chlorella and Bacillus with different nitrogen concentrations to investigate the possible effects of nitrate addition on the production of organic anions and phosphatases of the Chlorella-Bacillus communities by using metabolomic analysis.Chlorella-Bacillus biofertilizer significantly increased soil Olsen-P concentration via strong interactive effects correlating with the various nitrate addition amounts in the microcosm experiment. These effects were due mainly to reducing the algal diversity, soil pH, and changing dissolved organic matter (DOM) characteristics, especially increasing the humification index (HIX). The metabolomic analyses of co-culture confirm that pathways related to the biosynthesis of fatty acids and phosphatases production are enhanced when nitrogen levels are high.Chlorella-Bacillus biofertilizer has significantly interactive effects with nitrate addition on soil phosphorus bioavailability by influencing soil DOM, pH and production of organic anions and phosphatases. These insights are useful for optimizing bio-fertilizer-nitrate combinations for increasing phosphorus bioavailability thereby reducing chemical fertilizer requirements. [ABSTRACT FROM AUTHOR]

• Ag+ released from AgNPs has heavier impact on photosynthesis than intact AgNPs. • Ag+ blocks electron transport and damages phycobilisome of algae in periphyton. • Energy absorption is increased to maintain electron transfer in photosynthesis. • PSII and PSI work in complement to cope with stress by intact AgNPs and Ag+. Silver nanoparticles (AgNPs) including a mix of intact nanoparticle-Ag and 'free' Ag+ pose high risks to benthic photoautotrophs, but the photosynthetic responses of benthic microbial aggregates to AgNPs still remain largely unknown. Here, periphyton and Nostoc were used to elucidate the photosynthetic responses of benthic algae community to intact nanoparticle-Ag and Ag+. During exposure, both intact nanoparticle-Ag and Ag+ imposed negative effects on photosynthesis of benthic algae, but via different pathways. Specifically, Ag+ had stronger effects on damaging the oxygen-evolving complex (OEC) and thylakoid membrane than intact nanoparticle-Ag. Ag+ also suppressed electron transfer from Q A to Q B , and impaired phycobilisome. Intact nanoparticle-Ag inhibited the expression of PsbD and PsbL in PSII, but prompted the ROS scavenging capacity. In response to the stress of AgNPs, the benthic algae increased light energy absorption to maintain the electron transport efficiency, and up-regulated PSI reaction center protein (PsaA) to compensate the degraded PSII. These results reveal how intact nanoparticle-Ag and Ag+ influence electron transport, energy conversion and protein expression in the photosynthesis of periphyton, and provide deep insights into the responses of benthic photoautotrophs to different components of AgNPs. [ABSTRACT FROM AUTHOR]