Eutrophication-induced shifts cause diverse responses in the phoD community of a plateau freshwater lake.

Eutrophication is a critical environmental challenge affecting lakes globally. Mitigating trophic level under endogenous phosphorus release is an unsolved problem in eutrophic lakes. However, understanding the dynamics and assembly of microbial communities encoding the alkaline phosphatase (phoD community) and their responses during trophic transitions in eutrophic lakes is limited. In this study, we compared the composition and assembly mechanisms of phoD communities in four seasons in the Yilong Lake, a shallow lake of the Yunnan-Guizhou Plateau. The lake exhibits slightly eutrophic conditions in summer and mesotrophic conditions in spring, autumn, and winter. By analyzing seasonal variations, we observed that during summer, the relative abundance of Pseudomonas in the water had the highest value, while the Shannon-Wiener index of phoD communities was lowest. Mantel tests showed an increased Bray-Curtis dissimilarity of phoD communities in the water with rising eutrophication, a trend not observed in sediment. Notably, eutrophication heightened the homogeneity selection governing the assembly of phoD communities in water. The co-occurrence networks showed that the OTUs in the summer exhibited closer interconnections than those in other seasons. Additionally, the topological parameters from networks indicated that eutrophication is poised to instigate changes and modulate the dynamics of the microbial phoD community, resulting in markedly distinct seasonal behaviors. pH was identified as a critical factor directly influencing phoD community diversity via partial least squares path modeling (PLS-PM). This study shed light on our understanding of the seasonal dynamics of phoD communities and their pivotal role in phosphorus cycling in eutrophic lakes.

Lithology and elevated temperature impact phoD-harboring bacteria on soil available P enhancing in subtropical forests.

Plants are generally limited by soil phosphorus (P) deficiency in forest ecosystems. Soil available P is influenced by lithology, temperature, and soil microbes. However, the interactive effects of these factors on soil P availability in subtropical forests remain unclear. To assess their impacts, we measured soil inorganic and available P fractions and the diversity, composition, and co-occurrence network of phoD-harboring bacteria in two contrasting forest soils (lithosols in karst forests and ferralsols in non-karst forests) in the subtropical regions of southwestern China across six temperature gradients. The present results showed that the complexities in composition and network and the diversity indices of phoD-harboring bacteria were higher in the karst forest soils than those in the non-karst forest soils, with marked differences in composition. In both types of forest soils, the complexities of composition and networks and the diversity indices were higher in the high-temperature regions (mean annual temperature (MAT) > 16 °C) compared to the low-temperature regions (MAT <16 °C). Soil total inorganic and available P contents were lower in the karst forest soils compared to the non-karst forest soils. Soil total available P contents were lower in the high temperature regions than those in the low temperature regions in both forest soils, whereas soil total inorganic P contents were contrary. Variance partitioning analysis showed that soil inorganic and available P fractions were predominantly explained by lithology and its interaction with soil microbes and climate. The present findings demonstrate that soil P availability in subtropical forests of southwestern China is influenced by lithology and temperature, which regulate the diversity, composition, and network connectivity of phoD-harboring bacteria. Furthermore, this study highlights the significance of controlling the composition of phoD-harboring bacteria for mitigating plant P deficiency in karst ecosystems.

Biotic regulation of phoD-encoding gene bacteria on organic phosphorus mineralization in lacustrine sediments with distinct trophic levels.

Organic phosphorus (Po) mineralization hydrolyzed by alkaline phosphatase (APase) can replenish bioavailable P load in the sediment water ecosystem of lakes. However, the understanding about the interaction between P load and bacteria community encoding APase generation in the sediment are still limited. Different P pools in the sediments from Taihu Lake, China were measured using sequential extraction procedure. The APAase activity (APA) were obtained accompanying with enzymatic dynamical parameters Vmax and Km. The abundances and diversity of gene phoD-harboring bacterial communities were assessed using high throughput sequencing. The analysis results showed the decrease of potentially bioavailable P fractions including MgCl2-P and Fe-P along sampling gradient southwards together with active P concentrations in the water. Conversely, increasing APA and absolute abundance of phoD gene were found with the decreasing of P loads southwards. Positive correlation (p < 0.05) between absolute abundance and APA indicated that phoD-encoding bacteria manipulated the APA and Po mineralization. Negative correlation (p < 0.01) suggested that the APA was restrained by high P load and was promoted under low P condition. However, higher Vmax and Km values suggested that high mineralization potential of Po maintained the high concentrations of potentially bioavailable P even the APA was restricted. The abundance increase of predominant genus Cobetia (from 15.51 to 24.34 %) mirrored by the reduced Calothrix abundance (from 24.65 to 1036 %) was speculated to be responsible for the APA promotion under low P condition. Higher diversity indices in the high P scenario suggested that high P load stimulated the ecological diversity of gene phoD-encoding bacteria community. Generally, rare taxa such as Burkholderia having high connected degrees in bacterial communities together with abundant genera synergistically manipulated the phoD gene abundance and APase generation. Interaction between P fractions and bacteria encoding phoD gene determined the eutrophication status in the lacustrine ecosystem.

Soil microeukaryotic communities and phosphorus-cycling microorganisms respond to chloropicrin fumigation and azoxystrobin application.

Fumigants and fungicides are effective at controlling soil-borne pathogens but might also adversely affect soil beneficial microbes, such as soil phosphorus (P) solubilizing microbes, further altering nutrient cycling processes. Therefore, this study investigated the effects of the fumigant chloropicrin (CP) and the fungicide azoxystrobin (AZO) on soil microeukaryotes and P-cycling related soil bacteria through a greenhouse experiment. Soil microeukaryotic communities and bacterial communities containing two phosphomonoesterase encoding genes (phoC and phoD) were analysed using high-throughput sequencing methods. Results showed that, when applied at the field recommended application dosage, the fungicide AZO had no significant influence on the community structure of soil microeukaryotes and phoD-containing bacteria. However, in CP-fumigated soils, the soil microeukaryotic community composition changed from fungi-dominated to protist-dominated. CP fumigation significantly decreased the total phoC/phoD gene copy number but increased the relative abundance of some phoC/phoD-containing bacteria (such as Sinorhizobium and Streptomyces), which are significantly positively correlated to available P compositions in soil. The structural equation model (SEM) confirmed that CP fumigation could affect soil available P content directly by altering phoC-/phoD-containing bacteria, or indirectly by affecting phoC/phoD gene abundance and acid/alkaline phosphatases activity in soil. The inconsistent changes in phoC/phoD-containing bacteria, phoC/phoD gene number, and the phosphomonoesterase activities indicated that enzyme secretion may not be the only way for P solubilizing soil microorganisms to regulate P availability after soil fumigation. The outcome of this study can provide theoretical support for the design of soil beneficial microorganism recovery strategies and the regulation of phosphate fertilizer after soil fumigation.

Microbial mechanisms for improved soil phosphorus mobilization in monoculture conifer plantations by mixing with broadleaved trees.

Replanting broadleaved trees in monoculture conifer plantations has been shown to improve the ecological environment. However, not much is known about the distribution properties of soil phosphate-mobilizing bacteria (PMB) under different mixed plantings or how PMB affects biometabolism-driven phosphorus (P) bioavailability. The phoD and pqqC genes serve as molecular markers of PMB because they regulate the mobilization of organic (Po) and inorganic (Pi) P. Differences in soil bioavailable P concentration, phoD- and pqqC-harboring PMB communities, and their main regulators were analyzed using biologically-based P (BBP) and high-throughput sequencing approaches after combining coniferous trees (Pinus massoniana) and five individual broadleaved trees (Bretschneidera sinensis, Michelia maudiae, Cercidiphyllum japonicum, Manglietia conifera, and Camellia oleifera). The findings revealed that the contents of litter P, soil organic carbon (SOC), available Pi (CaCl2-P), and labile Po (Enzyme-P) were significantly higher in conifer-broadleaf mixed plantations than those in the monospecific Pinus massoniana plantations (PM), especially in the mixed stands with the introduction of Cercidiphyllum japonicum, Michelia maudiae, and Camellia oleifera. Conifer-broadleaf mixing had little effect on the abundance of phoD and pqqC genes but significantly altered species composition within the communities. Conifer-broadleaf mixing improved soil microbial habitat mainly by increasing the pH, increasing carbon source availability and nutrient content, decreasing exchangeable Fe3+ and Al3+ content, and decreasing the activation degrees of Fe and Al oxides in acidic soils. A small group of taxa (phoD: Bradyrhizobium, Tardiphaga, Nitratireductor, Mesorhizobium, Herbaspirillum, and Ralstonia; pqqC: Burkholderia, Variovorax, Bradyrhizobium, and Leptothrix) played a key role in the synthesis of P-related enzymes (e.g., alkaline phosphomonoesterase, ALP) and in lowering the levels of mineral-occluded (HCl-P) and chelated (Citrate-P) Pi. Overall, our findings highlight that mixing conifers and broadleaves could change the PMB communities that produce ALP and dissolve Pi to make P more bioavailable.

Divergent responses of rhizosphere soil phosphorus fractions and biological features of Salix psammophila to fertilization strategies under cadmium contamination.

Soil oligotrophy in areas heavily contaminated with heavy metals poses a significant challenge to vegetation establishment and phytoremediation processes. Phosphorus (P) cycling plays a critical role in global biogeochemical cycles, but there is limited understanding of its response to varying fertilization strategies and its correlation with phytoremediation effectiveness. This study primarily investigated the effects of various fertilization strategies, including nitrogen (N, 300 mg·kg-1), P (100 mg·kg-1), NP (combined N and P at 300 mg·kg-1 and 100 mg·kg-1, respectively), and HP (high P, 300 mg·kg-1) application, on rhizosphere soil P fractions and P-solubilizing microbial community (harboring phoD and phoC genes, respectively) of Salix psammophila under cadmium contamination. Application of NP significantly enhanced plant growth and cadmium accumulation, whereas HP inhibited cadmium bioaccumulation but promoted its translocation. Compared to untreated soil, N application promoted P cycling, leading to increases of 141.9 %, 60.4 %, and 10.3 % in Resin-Pi, diluted HCl-Pi, and conc.HCl-Pi, respectively. P application decreased organic phosphorus (Po) fractions by 24.4 % - 225.8 %, but N incorporation mitigated the declining trend in Po and augmented alkaline phosphatase activity. Fertilization strategies significantly regulated phoC- or phoD-harboring bacterial community structure, but their differential nutrient demands resulted in distinct responses. The phoD-harboring bacteria exhibited higher diversity and network complexity, with numerous biomarkers and fertilizer-sensitive OTUs discovered across treatments. Structural equation modeling (SEM) analysis indicated that phytoremediation efficiency was directly affected by Pi fractions, and phoD-harboring bacteria exhibited stronger associations with Pi fractions than phoC-harboring bacteria. In conclusion, our results reveal potential pathways through which fertilization strategies influence phytoremediation by affecting the structure of P-solubilizing microbial community. Furthermore, our study emphasizes the importance of combined N and P application in promoting Cd accumulation in plants, with high P levels appearing as an ideal fertilization strategy for phytoremediation targeting the harvest of aboveground biomass.

[Intensive Citrus Cultivation Suppresses Soil Phosphorus Cycling Microbial Activity].

Soil microbes are key drivers in regulating the phosphorus cycle. Elucidating the microbial mineralization process of soil phosphorus-solubilizing bacteria is of great significance for improving nutrient uptake and yield of crops. This study investigated the mechanism by which citrus cultivation affects the soil microbial acquisition strategy for phosphorus by measuring the abundance of the phoD gene, microbial community diversity and structure, and soil phosphorus fractions in the soils of citrus orchards and adjacent natural forests. The results showed that citrus cultivation could lead to a decrease in soil pH and an accumulation of available phosphorus in the soil, with a content as high as 112 mg·kg-1, which was significantly higher than that of natural forests (3.7 mg·kg-1). Citrus cultivation also affected the soil phosphorus fractions, with citrus soil having higher levels of soluble phosphorus (CaCl2-P), citrate-extractable phosphorus (Citrate-P), and mineral-bound phosphorus (HCl-P). The phosphorus fractions of natural forest soils were significantly lower than those of citrus soils, whereas the phoD gene abundance and alkaline phosphatase activity were significantly higher in natural forest soils than in citrus soils. High-throughput sequencing results showed that the Shannon diversity index of phosphate-solubilizing bacteria in citrus soils was 4.61, which was significantly lower than that of natural forests (5.35). The microbial community structure in natural forests was also different from that of citrus soils. In addition, the microbial community composition of phosphate-solubilizing bacteria in citrus soils was also different from that of natural forests, with the relative abundance of Proteobacteria being lower in natural forest soils than in citrus soils. Therefore, citrus cultivation led to a shift of soil microbial acquisition strategy for phosphorus, with external phosphorus addition being the main strategy in citrus soils, whereas microbial mineralization of organic phosphorus was the main strategy in natural forest soils to meet their growth requirements.

LPS-Dephosphorylating Cobetia amphilecti Alkaline Phosphatase of PhoA Family Divergent from the Multiple Homologues of Cobetia spp.

A highly active alkaline phosphatase (ALP) of the protein structural family PhoA, from a mussel gut-associated strain of the marine bacterium Cobetia amphilecti KMM 296 (CmAP), was found to effectively dephosphorylate lipopolysaccharides (LPS). Therefore, the aim of this work was to perform a comprehensive bioinformatics analysis of the structure, and to suggest the physiological role of this enzyme in marine bacteria of the genus Cobetia. A scrutiny of the CmAP-like sequences in 36 available Cobetia genomes revealed nine homologues intrinsic to the subspecies C. amphilecti, whereas PhoA of a distant relative Cobetia crustatorum JO1T carried an inactive mutation. However, phylogenetic analysis of all available Cobetia ALP sequences showed that each strain of the genus Cobetia possesses several ALP variants, mostly the genes encoding for PhoD and PhoX families. The C. amphilecti strains have a complete set of four ALP families' genes, namely: PhoA, PafA, PhoX, and two PhoD structures. The Cobetia marina species is distinguished by the presence of only three PhoX and PhoD genes. The Cobetia PhoA proteins are clustered together with the human and squid LPS-detoxifying enzymes. In addition, the predicted PhoA biosynthesis gene cluster suggests its involvement in the control of cellular redox balance, homeostasis, and cell cycle. Apparently, the variety of ALPs in Cobetia spp. indicates significant adaptability to phosphorus-replete and depleted environments and a notable organophosphate destructor in eco-niches from which they once emerged, including Zostera spp. The ALP clusterization and degree of similarity of the genus-specific biosynthetic genes encoding for ectoine and polyketide cluster T1PKS, responsible for sulfated extracellular polysaccharide synthesis, coincide with a new whole genome-based taxonomic classification of the genus Cobetia. The Cobetia strains and their ALPs are suggested to be adaptable for use in agriculture, biotechnology and biomedicine.

Warming enhances the negative effects of shrub removal on phosphorus mineralization potential.

Shrubs have developed various mechanisms for soil phosphorus utilization. Shrub encroachment caused by climate warming alters organic phosphorus mineralization capability by promoting available phosphorus absorption and mediating root exudates. However, few studies have explored how warming regulates the effects of dominant shrubs on soil organic phosphorus mineralization capability. We provide insights into warming, dominant shrub removal, and their interactive effects on the soil organic phosphorus mineralization potential in the Qinghai-Tibetan Plateau. Real-time polymerase chain reaction was used to quantify the soil microbial phosphatase genes (phoC and phoD), which can characterize the soil organic phosphate mineralization potential. We found that warming had no significant effect on the soil organic phosphate-mineralized components (total phosphate, organic phosphate, and available phosphate), genes (phoC and phoD), or enzymes (acid and alkaline phosphatases). Shrub removal negatively influenced the organic phosphate-mineralized components and genes. It significantly decreased soil organic phosphate mineralization gene copy numbers only under warming conditions. Warming increased fungal richness and buffered the effects of shrub removal on bacterial richness and gene copy numbers. However, the change in the microbial community was not the main factor affecting organic phosphate mineralization. We found only phoC copy number had significant correlation to AP. Structural equation modelling revealed that shrub removal and the interaction between warming and shrub removal had a negative direct effect on phoC copy numbers. We concluded that warming increases the negative effect of shrub removal on phosphorus mineralization potential, providing a theoretical basis for shrub encroachment on soil phosphate mineralization under warming conditions.

Vegetation recovery reshapes the composition and enhances the network connectivity of phoD-harboring microorganisms to promote P availability in a karst ecosystem.

Soil phoD-harboring microorganisms can facilitate phosphorus (P) transformation and increase the available P (AP) in P-limited soils; however, the mechanism by which these microorganisms enhance AP throughout the vegetation recovery process of karst ecosystems is poorly understood. Accordingly, this study investigates the effect of vegetation recovery on soil AP and the community composition and network connectivity of phoD-harboring microorganisms to elucidate the mechanism by which phoD-harboring microorganisms enhance soil AP in the four vegetation recovery stages (i.e., grassland, shrubland, shrub-arbor forest, and arbor forest) in a karst ecosystem. Results show that soil total P, AP, and microbial biomass P concentrations, as well as alkaline phosphatase activities, litter and soil nutrients, and plant diversity indices (Shannon-Wiener and Pielou) increase with advancing vegetation recovery. Moreover, the diversity indices (Shannon-Wiener and Simpson) and network complexity of the phoD-harboring microorganisms also increase with advancing vegetation recovery, leading to distinct communities among the four recovery stages. Rhizobiales, Pseudomonadales, and Burkholderiales comprise the dominant phoD-harboring microorganism orders. The relative abundances of Pseudomonadales and Burkholderiales increase with advancing vegetation recovery; Rhizobiales is the highest in shrubland and the lowest in grassland. The structural equation model results show that advanced vegetation recovery is associated with increased plant diversity, litter nutrients, and soil nutrients. The network connectivity is enhanced with advancing vegetation recovery accompanied by increasing soil phosphatase activity and P availability. These results suggest that regulating the phoD-harboring microorganism composition and network connectivity is essential to alleviate plant P limitation in karst ecosystems.

Coupling of cylindrospermopsin and pho-harboring Verrucomicrobia supports the formation of Raphidiopsis blooms in low-phosphorus waters.

Cylindrospermopsin (CYN) can induce phytoplankton community to secrete alkaline phosphatase (ALP), which is one of the important strategies for the bloom-forming cyanobacterium Raphidiopsis to thrive in extremely low-phosphorus (P) waters. However, how bacterioplankton community, another major contributor to ALPs in waters, couples to Raphidiopsis through CYN, and the role of this coupling in supporting the dominance of Raphidiopsis in nature remain largely unknown. Here, we conducted microcosm experiments to address this knowledge gap, using a combination of differential filtration-based and metagenomics-based methods to identify the sources of ALPs. We found that, compared with algal-derived ALPs, bacteria-derived ALPs exhibited a more pronounced and sensitive response to CYN. This response to CYN was enhanced under low-P conditions. Interestingly, we found that Verrucomicrobia made the largest contribution to the total abundance of pho genes, which encode ALPs. Having high gene abundance of the CYN-sensing PI3K-AKT signaling pathway, Verrucomicrobia's proportion increased with higher concentrations of CYN under low-P conditions, thereby explaining the observed increase in pho gene abundance. Compared with other cyanobacterial genera, Raphidiopsis had a higher abundance of the pst gene. This suggests that Raphidiopsis exhibited a greater capacity to uptake the inorganic P generated by ALPs secreted by other organisms. Overall, our results reveal the mechanism of CYN-induced ALP secretion and its impact on planktonic P-cycling, and provide valuable insights into the role of CYN in supporting the formation of Raphidiopsis blooms.

Phosphorus fertiliser application mitigates the negative effects of microplastic on soil microbes and rice growth.

Soil microplastics (MPs) have attracted widespread attention recently. Most studies have explored how soil MPs affect the soil's physicochemical parameters, matter circulation, and soil microbial community assembly. Similarly, a key concern in agricultural development has been the use of phosphorus (P) fertiliser, which is essential for plant health and development. However, the relationship between MPs and phosphate fertilisers and their effects on the soil environment and plant growth remains elusive. This study assessed the influence of adding low-density polyethylene MPs (1%) with different phosphate fertiliser application rates on microbial communities and rice biomass. Our results showed that MPs changed the structure of soil bacterial and phoD-harbouring microbial communities in the treatment with P fertiliser at the same level and suppressed the interactions of phoD-harbouring microorganisms. In addition, we found that MPs contamination inhibited rice growth; however, the inclusion of P fertiliser in MP-contaminated soils reduced the inhibitory action of MPs on rice growth, probably because the presence with P fertiliser promoted the uptake of NO3--N by rice in MP-contaminated soils. Our results provide further insights into guiding agricultural production, improving agricultural management, and rationally applying phosphate fertilisers in the context of widespread MPs pollution and global P resource constraints.

Organic phosphorus levels change the hyphosphere phoD-harboring bacterial community of Funneliformis mosseae.

The phoD-harboring bacterial community is responsible for organic phosphorus (P) mineralization in soil and is important for understanding the interactions between arbuscular mycorrhizal (AM) fungi and phosphate-solubilizing bacteria (PSB) at the community level for organic P turnover. However, current understanding of the phoD-harboring bacterial community associated with AM fungal hyphae responses to organic P levels remains incomplete. Here, two-compartment microcosms were used to explore the response of the phoD-harboring bacterial community in the hyphosphere to organic P levels by high-throughput sequencing. Extraradical hyphae of Funneliformis mosseae enriched the phoD-harboring bacterial community and organic P levels significantly altered the composition of the phoD-harboring bacterial community in the Funneliformis mosseae hyphosphere. The relative abundance of dominant families Pseudomonadaceae and Burkholderiaceae was significantly different among organic P treatments and were positively correlated with alkaline phosphatase activity and available P concentration in the hyphosphere. Furthermore, phytin addition significantly decreased the abundance of the phoD gene, and the latter was significantly and negatively correlated with available P concentration. These findings not only improve the understanding of how organic P influences the phoD-harboring bacterial community but also provide a new insight into AM fungus-PSB interactions at the community level to drive organic P turnover in soil.

Alkaline Phosphatase PhoD Mutation Induces Fatty Acid and Long-Chain Polyunsaturated Fatty Acid (LC-PUFA)-Bound Phospholipid Production in the Model Diatom Phaeodactylum tricornutum.

With rapid growth and high lipid contents, microalgae have become promising environmentally friendly candidates for renewable biodiesel and health supplements in our era of global warming and energy depletion. Various pathways have been explored to enhance algal lipid production, especially gene editing. Previously, we found that the functional loss of PhoD-type alkaline phosphatase (AP), a phosphorus-stress indicator in phytoplankton, could lead to increased lipid contents in the model diatom Phaeodactylum tricornutum, but how the AP mutation may change lipid composition remains unexplored. This study addresses the gap in the research and investigates the effects of PhoD-type AP mutation on the lipid composition and metabolic regulation in P. tricornutum using transcriptomic and lipidomic analyses. We observed significantly modified lipid composition and elevated production of fatty acids, lysophosphatidylcholine, lysophosphatidylethanolamine, ceramide, phosphatidylinositol bisphosphate, and monogalactosylmonoacylglycerol after PhoD_45757 mutation. Meanwhile, genes involved in fatty acid biosynthesis were upregulated in mutant cells. Moreover, the mutant exhibited increased contents of ω-3 long-chain polyunsaturated fatty acid (LC-PUFA)-bound phospholipids, indicating that PhoD_45757 mutation could improve the potential bioavailability of PUFAs. Our findings indicate that AP mutation could influence cellular lipid synthesis and probably redirect carbon toward lipid production and further demonstrate that AP mutation is a promising approach for the development of high-value microalgal strains for biomedical and other applications.

Short-Term Impact of Recycling-Derived Fertilizers on Their P Supply for Perennial Ryegrass (Lolium perenne).

Various nutrient recycling technologies are currently under development in order to alleviate the dependency of non-renewable raw material for the production of mineral phosphorus fertilizers commonly used in agriculture. The resulting products, such as struvites and ashes, need to be assessed for their application as so-called recycling-derived fertilizers (RDFs) in the agricultural sector prior to commercialization. Here, we conducted a short-term (54 days) trial to investigate the impact of different phosphorus fertilizers on plant growth and the soil P cycling microbiota. Lolium perenne was grown with application of superphosphate (SP) as inorganic fertilizer, two ashes (poultry litter ash (PLA) and sewage sludge ash (SSA)), and two struvites (municipal wastewater struvite (MWS) and commercial CrystalGreen® (CGS)) applied at 20 and 60 kg P ha-1 in four replicates. A P-free control (SP0) was also included in the trial. Struvite application increased plant dry weights, and available P acid phosphatase activity was significantly improved for struvites at the high P application rate. The ash RDFs showed a liming effect at 60 kg P ha-1, and PLA60 negatively affected acid phosphatase activity, while PLA20 had significantly lower phoD copy numbers. P mobilization from phosphonates and phytates was not affected. TCP solubilization was negatively affected by mineral SP fertilizer application at both P concentrations. The bacterial (16S and phoD) communities were only marginally affected by the tested P fertilizers. Overall, struvites appeared to be a suitable substitute for superphosphate fertilization for Irish L. perenne pastures.

Effects of different remediation methods on phosphorus transformation and availability.

The effects of different heavy metal pollution remediation methods on soil nutrient transformation and soil health remain unclear. In this study, the effects of phytoextraction (PE) and passivation remediation (PR) on Cd-polluted soil phosphorus transformation and availability were compared by pot experiment. The results showed that PE significantly reduced the concentrations of total and available Cd (both H2O-Cd and DTPA-Cd) in soil, PR also decreased available Cd content but had no significant effect on total Cd content. PE slightly increased soil pH and NH4+-N content, while PR significantly increased soil pH, NO3--N and AK content. PE promoted the conversion of stable P (including HCl-Pi and residual-Pt), and increased the content of labile P (including H2O-Pi, NaHCO3-Pi and NaHCO3-Po) and the proportion of moderately labile P (including NaOH-Pi and NaOH-Po), while PR showed the opposite trend. PE showed a higher soil phoC gene abundance and acid phosphatase (ACP) activity, while PR showed a higher phoD gene copies and alkaline phosphatase (ALP) activity. Soil bacteria and phoD-harboring bacteria community was significantly affected by remediation methods and soil types. Compared with PR, PE reduced phoD-harboring bacterial diversity but significantly increased the abundance of genera associated with P dissolution (Streptomyces) and P conversion (Bradyrhizobium and Frankia), both of which were significantly positively correlated with labile P or moderately labile P. In general, compared with PR, PE can effectively remove soil Cd pollution, while maintaining a higher content of labile P and a higher proportion of moderately labile P, which can be considered as a green and sustainable remediation strategy conducive to soil quality.

Linking soil phosphorus availability and phosphatase functional genes to coastal marsh erosion: Implications for nutrient cycling and wetland restoration.

Accelerated marsh erosion caused by climate change and human activity may have important implications for nutrient cycling and availability. However, how erosion affects phosphorus (P) transformation and microbial function in subtropical coastal marshes remains largely unknown. Here we assessed soil P fractions, availability and the phoD-harboring bacterial community along a marsh erosion gradient (non-eroded, lightly eroded, and heavily eroded). We showed that marsh erosion caused a shift in P fractions, leading to a decrease in P availability and a reduction in concentrations of labile P, moderately labile P, and stable P by 20 %, 9 %, and 17 % respectively. The abundance and diversity of phoD phosphatase genes decreased dramatically along the erosion gradient and were lower at heavily eroded sites than at non-eroded sites. Marsh erosion reshaped phoD gene community composition, and Corallococcus, Amycolatopsis, and Phaeobacter were identified as the dominant phoD-harboring microbes. Notably, marsh erosion reduced the complexity and stability of the phoD-harboring bacterial network, and heavily eroded sites have fewer network edges and nodes than non-eroded sites. The dynamics of soil P fractions, availability, and phoD-harboring bacterial communities driven by marsh erosion are largely shaped by substrate availability and soil properties (e.g., nutrients, pH, electrical conductivity, and moisture). Additionally, strong linkages between P availability and the abundance and diversity of phosphatase genes following erosion, suggest that phosphatase drives P mineralization and dissolution, and erosion weakens the regulation of P transformation by reshaping the phoD phosphatase gene community. Our findings indicate that marsh erosion alters soil P fractions and phoD-harboring bacterial communities, which weakens microbial regulation of P transformation and availability, thereby significantly reducing soil P pools and availability. Our findings broaden understanding of the impacts of coastal erosion on nutrient balance and ecosystem function, offering valuable perspectives that could inform wetland restoration and coastal management strategies.

Long-term nitrogen fertilization and sweetpotato cultivation in the wheat-sweetpotato rotation system decrease alkaline phosphomonoesterase activity by regulating soil phoD-harboring bacteria communities.

The alkaline phosphomonoesterase (ALP)-harboring community (phoD-harboring community) plays a crucial role in the conversion of organic phosphorus (P) into available P (AP). However, the response mechanisms of phoD-harboring communities to fertilization strategies, crop types, and their interactions within the wheat-sweetpotato rotation are poorly understood. A nine-year field experiment of different fertilization strategies was established under the wheat-sweetpotato rotation. After harvesting the crop, we collected soil samples without fertilization (CK), inorganic NK fertilization (NK), inorganic NPK fertilization (NPK), and a combined application of inorganic NPK and organic fertilizer (NPKM). We employed high-throughput sequencing and enzymology techniques to analyze the composition and functional activity of phoD-harboring bacterial communities as well as their correlation with soil physicochemical properties. The results showed that long-term nitrogen (N) fertilization, especially inorganic N, significantly reduced soil pH and ALP activity while increasing AP compared with CK. The AP content in sweetpotato season was significantly higher than that in wheat season. Inorganic N fertilization dramatically reshaped the communities of phoD-harboring bacteria and decreased diversity. The phoD-harboring bacterial communities in sweetpotato season were significantly different from those in wheat season. The N fertilization significantly reduced the relative abundance of Acuticoccus, Methylibium, Rhizobacter, and Roseivivax, which was positively correlated with ALP activity. These groups in sweetpotato season decreased significantly compared with wheat season. A structural equation model indicates that pH and AP play a significant role in regulating the phoD-harboring bacteria communities, ALP activity, and their interactions. We demonstrate that fertilization strategies and crop types have a substantial impact on the phoD-harboring bacteria communities and functions, which are closely linked to soil pH and AP levels. Our study highlights the detrimental effects of soil acidification resulting from inorganic N fertilization on P-cycling bacterial communities and functions. However, the combination of inorganic and organic fertilizer can mitigate these adverse effects.

Tuber indicum and T. lijiangense colonization differentially regulates plant physiological responses and mycorrhizosphere bacterial community of Castanopsis rockii seedlings.

Black truffles and white truffles are widely studied around the world, but their effects on plant growth and physiological responses, and on the mycorrhizosphere bacterial community of the host plant remain unclear. Here, mycorrhizal colonization of Castanopsis rockii by Tuber indicum (Chinese black truffle) and T. lijiangense (Chinese white truffle), respectively, was induced in a greenhouse study, and their effects on host growth, physiological responses and mycorrhizosphere bacterial communities were compared. The results show that colonization of both Tuber species significantly increased leaf photosynthetic rate, leaf P concentration and mycorrhizosphere acid phosphatase activity, as well as richness of mycorrhizosphere bacterial communities of C. rockii seedlings. However, T. indicum colonization on the one hand significantly decreased tartrate content, bacterial acid phosphatase, phoC gene abundance in the mycorrhizosphere, and peroxidase (POD) activity of ectomycorrhizal root tips, but on the other hand increased mycorrhizosphere pH and superoxide dismutase (SOD) of ectomycorrhizal root tips, compared to T. lijiangense colonization. Moreover, principal coordinate and ß-diversity analyses show significant differences in mycorrhizosphere bacterial community composition between T. indicum and T. lijiangese colonized C. rockii seedlings. Finally, the relative abundance of the bacterium Agromyces cerinus significantly correlated to mycorrhizosphere acid phosphatase activity and leaf P concentration, suggesting that this bacterium might play an important role in P mobilization and acquisition. Overall, these results suggest that T. indicum and T. lijiangense differently regulate their host plant's physiological responses and mycorrhizosphere bacterial community.

How phoD-harboring functional microbial populations trigger the release risk of phosphorus in water sediment system of Shijiuhu Lake, China after experiencing the transseasonal shift.

Excessive phosphorus (P) enrichment is the critical cause of eutrophication in the lake water. Organic P (Po) mineralization processes induced by alkaline phosphatase (APase) regulated by phoD-encoding microorganisms in the lake ecosystems was still ambiguous due to the transseasonal shift of water temperatures and depths. Different P pools in the water and sediments of Shijiuhu Lake at varied seasons were measured using chemical extraction methods and solution 31P NMR. The alkaline phosphatase activity (APA) in the sediments were assessed together with enzyme kinetic parameters. The abundances and compositions of microbial communities encoding functional gene phoD were also obtained using high-throughput sequencing. The results showed that Po concentrations remarkably increased from winter toward spring when having higher water depths due to the terrigenous input and biomass deposition. Noteworthy elevation in the PO43- concentration was observed in the interstitial water during the spring, particularly at around 5 cm sediment depth with value reaching as high as 0.43 mg/L. The degradation and mineralization of momoesters and diesters with higher concentrations in the sediments of spring aggravated the PO43- load in the interstitial water. Higher APA reaching 91.6 µg/(g·h) in spring was responsible for the mineralization of Po. Remarkably upwards increasing of absolute abundance of phoD-encoding gene in spring reaching up to 2.6 times of that in winter facilitated the generation of APA in spring. Cobetia and Calothrix followed by Aquabacterium and Mitsuaria were the most abundant phoD-encoding genera with relative abundance > 4%. Weakly positive correlation between dominant bacterial genera and APA and P fractions suggested that low-abundance genera was also involved in the APA generation and Po hydrolysis. These results indicate that spring with high water temperature and depth facilitate the mineralization of Po in the sediment and increase of labile PO43- load in the water, further provide valuable information for the management of eutrophic lakes.