Developing robust protein analysis profiles to identify bacterial acid phosphatases in genomes and metagenomic libraries

Characterization of an extremophile bacterial acid phosphatase derived from metagenomics analysis

Acid phosphatases are enzymes that play a crucial role in the hydrolysis of various organophosphorous molecules. A putative acid phosphatase called FS6 was identified using genetic profiles and sequences from different environments. FS6 showed high sequence similarity to type C acid phosphatases and retained more than 30% of consensus residues in its protein sequence. A histidine-tagged recombinant FS6 produced in Escherichia coli exhibited extremophile properties, functioning effectively in a broad pH range between 3.5 and 8.5. The enzyme demonstrated optimal activity at temperatures between 25 and 50°C, with a melting temperature of 51.6°C. Kinetic parameters were determined using various substrates, and the reaction catalysed by FS6 with physiological substrates was at least 100-fold more efficient than with p-nitrophenyl phosphate. Furthermore, FS6 was found to be a decamer in solution, unlike the dimeric forms of crystallized proteins in its family.

The Shigella flexneri virulence factor apyrase is released inside eukaryotic cells to hijack host cell fate

IMPORTANCE

In this paper, we demonstrated that apyrase is released within the host cell cytoplasm during infection to target the intracellular ATP pool. By degrading intracellular ATP, apyrase contributes to prevent caspases activation, thereby inhibiting the activation of pyroptosis in infected cells. Our results show, for the first time, that apyrase is involved in the modulation of host cell survival, thereby aiding this pathogen to dampen the inflammatory response. This work adds a further piece to the puzzle of Shigella pathogenesis. Due to its increased spread worldwide, prevention and controlling strategies are urgently needed. Overall, this study highlighted apyrase as a suitable target for an anti-virulence therapy to tackle this pathogen.

Phosphate-Solubilizing Bacteria: Advances in Their Physiology, Molecular Mechanisms and Microbial Community Effects

Phosphorus is an essential nutrient for all life on earth and has a major impact on plant growth and crop yield. The forms of phosphorus that can be directly absorbed and utilized by plants are mainly HPO42- and H2PO4-, which are known as usable phosphorus. At present, the total phosphorus content of soils worldwide is 400-1000 mg/kg, of which only 1.00-2.50% is plant-available, which seriously affects the growth of plants and the development of agriculture, resulting in a high level of total phosphorus in soils and a scarcity of available phosphorus. Traditional methods of applying phosphorus fertilizer cannot address phosphorus deficiency problems; they harm the environment and the ore material is a nonrenewable natural resource. Therefore, it is imperative to find alternative environmentally compatible and economically viable strategies to address phosphorus scarcity. Phosphorus-solubilizing bacteria (PSB) can convert insoluble phosphorus in the soil into usable phosphorus that can be directly absorbed by plants, thus improving the uptake and utilization of phosphorus by plants. However, there is no clear and systematic report on the mechanism of action of PSB. Therefore, this paper summarizes the discovery process, species, and distribution of PSB, focusing on the physiological mechanisms outlining the processes of acidolysis, enzymolysis, chelation and complexation reactions of PSB. The related genes regulating PSB acidolysis and enzymatic action as well as genes related to phosphate transport and the molecular direction mechanism of its pathway are examined. The effects of PSB on the structure and abundance of microbial communities in soil are also described, illustrating the mechanism of how PSB interact with microorganisms in soil and indirectly increase the amount of available phosphorus in soil. And three perspectives are considered in further exploring the PSB mechanism in utilizing a synergistic multi-omics approach, exploring PSB-related regulatory genes in different phosphorus levels and investigating the application of PSB as a microbial fungicide. This paper aims to provide theoretical support for improving the utilization of soil insoluble phosphorus and providing optimal management of elemental phosphorus in the future.

Phosphate-solubilizing bacteria: Their agroecological function and optimistic application for enhancing agro-productivity

Phosphorus (P) is a limiting nutrient in the soil-plant nutrient cycling. Although the exogenous application of chemical P fertilizers can satisfy crop P requirements during critical growth phases. While excessive P fertilizers use results in low phosphorus acquisition efficiency (PAE), it has serious environmental consequences and hastens the depletion of P mineral reserves. Phosphate-solubilizing bacteria (PSB) have the potential to make insoluble phosphate available to plants through solubilization and mineralization, increasing crop yields while maintaining environmental sustainability. Existing reviews mainly focus on the beneficial effects of PSB on crop performance and related mechanisms, while few of them elucidate the action mechanisms of PSB in soil-microbe-plant interactions for crop cultivation with high yield efficiency. Hence, this study provides a comprehensive review of the physicochemical and molecular mechanisms (e.g., root exudates, extracellular polysaccharides, organic acids, phosphatases, and phosphate-specific transport systems) of PSB to facilitate the P cycle in the soil-plant systems. Further, the potential of commercial applications of PSB (e.g., genetic engineering, seed priming and coating) are also discussed in order to highlight their contribution to sustainable agriculture. Finally, existing challenges and future prospects in agricultural applications are proposed. In conclusion, we firmly believe that PSB represent a highly significant biotechnological tool for enhancing agricultural productivity and offers a wide range of extensive potential applications.

Abundance and phylogenetic distribution of eight key enzymes of the phosphorus biogeochemical cycle in grassland soils

Grassland biomes provide valuable ecosystem services, including nutrient cycling. Organic phosphorus (Po) represents more than half of the total P in soils. Soil microorganisms release organic P through enzymatic processes, with alkaline phosphatases, acid phosphatases and phytases being the key P enzymes involved in the cycling of organic P. This study analysed 74 soil metagenomes from 17 different grassland biomes worldwide to evaluate the distribution and abundance of eight key P enzymes (PhoD, PhoX, PhoA, Nsap-A, Nsap-B, Nsap-C, BPP and CPhy) and their relationship with environmental factors. Our analyses showed that alkaline phosphatase phoD was the dataset's most abundant P-enzyme encoding genes, with a wide phylogenetic distribution. Followed by the acid phosphatases Nsap-A and Nsap-C showed similar abundance but a different distribution in their respective phylogenetic trees. Multivariate analyses revealed that pH, Tmax , SOC and soil moisture were associated with the abundance and diversity of all genes studied. PhoD and phoX genes strongly correlated with SOC and clay, and the phoX gene was more common in soils with low to medium SOC and neutral pH. In particular, P-enzyme genes tended to respond in a positively correlated manner among them, suggesting a complex relationship of abundance and diversity among them.

PCycDB: a comprehensive and accurate database for fast analysis of phosphorus cycling genes

BACKGROUND

Phosphorus (P) is one of the most essential macronutrients on the planet, and microorganisms (including bacteria and archaea) play a key role in P cycling in all living things and ecosystems. However, our comprehensive understanding of key P cycling genes (PCGs) and microorganisms (PCMs) as well as their ecological functions remains elusive even with the rapid advancement of metagenome sequencing technologies. One of major challenges is a lack of a comprehensive and accurately annotated P cycling functional gene database.

RESULTS

In this study, we constructed a well-curated P cycling database (PCycDB) covering 139 gene families and 10 P metabolic processes, including several previously ignored PCGs such as pafA encoding phosphate-insensitive phosphatase, ptxABCD (phosphite-related genes), and novel aepXVWPS genes for 2-aminoethylphosphonate transporters. We achieved an annotation accuracy, positive predictive value (PPV), sensitivity, specificity, and negative predictive value (NPV) of 99.8%, 96.1%, 99.9%, 99.8%, and 99.9%, respectively, for simulated gene datasets. Compared to other orthology databases, PCycDB is more accurate, more comprehensive, and faster to profile the PCGs. We used PCycDB to analyze P cycling microbial communities from representative natural and engineered environments and showed that PCycDB could apply to different environments.

CONCLUSIONS

We demonstrate that PCycDB is a powerful tool for advancing our understanding of microbially driven P cycling in the environment with high coverage, high accuracy, and rapid analysis of metagenome sequencing data. The PCycDB is available at https://github.com/ZengJiaxiong/Phosphorus-cycling-database . Video Abstract.

Strategies of organic phosphorus recycling by soil bacteria: acquisition, metabolism, and regulation

Critical to meeting cellular phosphorus (P) demand, soil bacteria deploy a number of strategies to overcome limitation in inorganic P (P_i ) in soils. As a significant contributor to P recycling, soil bacteria secrete extracellular enzymes to degrade organic P (P_o ) in soils into the readily bioavailable P_i . In addition, several P_o compounds can be transported directly via specific transporters and subsequently enter intracellular metabolic pathways. In this review, we highlight the strategies that soil bacteria employ to recycle P_o from the soil environment. We discuss the diversity of extracellular phosphatases in soils, the selectivity of these enzymes towards various P_o biomolecules and the influence of the soil environmental conditions on the enzyme's activities. Moreover, we outline the intracellular metabolic pathways for P_o biosynthesis and transporter-assisted P_o and P_i uptake at different P_i availabilities. We further highlight the regulatory mechanisms that govern the production of phosphatases, the expression of P_o transporters and the key metabolic changes in P metabolism in response to environmental P_i availability. Due to the depletion of natural resources for P_i , we propose future studies needed to leverage bacteria-mediated P recycling from the large pools of P_o in soils or organic wastes to benefit agricultural productivity.

Extremophile enzymes for food additives and fertilizers

The use of extremophile enzymes for industrial purposes has become very significant since the beginning of this century and it is envisaged an ample use of enzymes for environmental applications (fertilisers, food and feed additives, biodegradation, pharma) as well as in the biosynthesis of compounds through design of novel biosynthetic pathways.

Shifts in the rhizobiome during consecutive in planta enrichment for phosphate-solubilizing bacteria differentially affect maize P status

Phosphorus (P) is despite its omnipresence in soils often unavailable for plants. Rhizobacteria able to solubilize P are therefore crucial to avoid P deficiency. Selection for phosphate-solubilizing bacteria (PSB) is frequently done in vitro; however, rhizosphere competence is herein overlooked. Therefore, we developed an in planta enrichment concept enabling simultaneous microbial selection for P-solubilization and rhizosphere competence. We used an ecologically relevant combination of iron- and aluminium phosphate to select for PSB in maize (Zea mays L.). In each consecutive enrichment, plant roots were inoculated with rhizobacterial suspensions from plants that had grown in substrate with insoluble P. To assess the plants' P statuses, non-destructive multispectral imaging was used for quantifying anthocyanins, a proxy for maize's P status. After the third consecutive enrichment, plants supplied with insoluble P and inoculated with rhizobacterial suspensions showed a P status similar to plants supplied with soluble P. A parallel metabarcoding approach uncovered that the improved P status in the third enrichment coincided with a shift in the rhizobiome towards bacteria with plant growth-promoting and P-solubilizing capacities. Finally, further consecutive enrichment led to a functional relapse hallmarked by plants with a low P status and a second shift in the rhizobiome at the level of Azospirillaceae and Rhizobiaceae.

The soil crisis: the need to treat as a global health problem and the pivotal role of microbes in prophylaxis and therapy

Soil provides a multitude of services that are essential to a healthily functioning biosphere and continuity of the human race, such as feeding the growing human population and the sequestration of carbon needed to counteract global warming. Healthy soil availability is the limiting parameter in the provision of a number of these services. As a result of anthropogenic abuses, and natural and global warming-promoted extreme weather events, Planet Earth is currently experiencing an unprecedented crisis of soil deterioration, desertification and erosive loss that increasingly prejudices the services it provides. Such services are pivotal to the Sustainability Development Goals formulated by the United Nations. Immediate and coordinated action on a global scale is urgently required to slow and ultimately reverse the loss of healthy soils. Despite the 'dirt-dust', non-vital appearance of soil, it is a highly dynamic living entity, whose life is overwhelmingly microbial. The soil microbiota, which constitutes the greatest reservoir and donor of microbial diversity on Earth, acts as a vast bioreactor, mediating a myriad of chemical reactions that turn the biogeochemical cycles, recycle wastes, purify water, and underpin the multitude of other services soil provides. Fuelling the belowground microbial bioreactor is the aboveground plant and photosynthetic surface microbial life which captures solar energy, fixes inorganic CO2 to organic carbon, and channels fixed carbon and energy into soil. In order to muster an effective response to the crisis, to avoid further deterioration, and to restore unhealthy soils, we need a new and coherent approach, namely to deal with soils worldwide as patients in need of health care and create (i) a public health system for development of effective policies for land use, conservation, restoration, recommendations of prophylactic measures, monitoring and identification of problems (epidemiology), organizing crisis responses, etc., and (ii) a healthcare system charged with soil care: the promotion of good practices, implementation of prophylaxis measures, and institution of therapies for treatment of unhealthy soils and restoration of drylands. These systems need to be national but there is also a desperate need for international coordination. To enable development of effective, evidence-based strategies that will underpin the efforts of soil healthcare systems, a substantial investment in wide-ranging interdisciplinary research on soil health and disease is mandatory. This must lead to a level of understanding of the soil:biota functionalities underlying key ecosystem services that enables formulation of effective diagnosis-prophylaxis-therapy pathways for sustainable use, protection and restoration of different types of soil resources in different climatic zones. These conservation-regenerative-restorative measures need to be complemented by an educative-political-economic-legislative framework that provides incentives encouraging soil care: knowledge, policy, economic and others, and laws which promote international adherence to the principles of restorative soil management. And: we must all be engaged in improving soil health; everyone has a duty of care (https://www.bbc.co.uk/ideas/videos/why-soil-is-one-of-the-most-amazing-things-on-eart/p090cf64). Creative application of microbes, microbiomes and microbial biotechnology will be central to the successful operation of the healthcare systems.