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It is generally claimed that glyphosate kills undesired plants by affecting the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) enzyme, disturbing the shikimate pathway. However, the mechanisms leading to plant death may also be related to secondary or indirect effects of glyphosate on plant physiology. Moreover, some plants can metabolize glyphosate to aminomethylphosphonic acid (AMPA) or be exposed to AMPA from different environmental matrices. AMPA is a recognized phytotoxin, and its co-occurrence with glyphosate could modify the effects of glyphosate on plant physiology. The present review provides an overall picture of alterations of plant physiology caused by environmental exposure to glyphosate and its metabolite AMPA, and summarizes their effects on several physiological processes. It particularly focuses on photosynthesis, from photochemical events to C assimilation and translocation, as well as oxidative stress. The effects of glyphosate and AMPA on several plant physiological processes have been linked, with the aim of better understanding their phytotoxicity and glyphosate herbicidal effects.

Key Points Organophosphonates are ancient molecules that predate phosphates as the most abundant form of P in the biosphere. They contain the chemically stable C–P bond. Synthetic phosphonates have a wide range of technological applications in the agricultural, chemical and pharmaceutical industries. Biogenic phosphonates provide alternative nutrient sources for organisms in oligotrophic environments, thereby playing a central role in global P cycling. There have been several recent significant advances in our understanding of the biochemistry and genetics of microbial phosphonate metabolism, as well as insights into the part played by these compounds and the organisms engaged in their environmental turnover. Organophosphonates contain the chemically stable C–P bond and are the most abundant form of P in the biosphere. McGrath and colleagues review recent advances in our understanding of microbial phosphonate metabolism and the role of these compounds in the global P cycle. Organophosphonates are ancient molecules that contain the chemically stable C–P bond, which is considered a relic of the reducing atmosphere on primitive earth. Synthetic phosphonates now have a wide range of applications in the agricultural, chemical and pharmaceutical industries. However, the existence of C–P compounds as contemporary biogenic molecules was not discovered until 1959, with the identification of 2-aminoethylphosphonic acid in rumen protozoa. Here, we review advances in our understanding of the biochemistry and genetics of microbial phosphonate metabolism, and discuss the role of these compounds and of the organisms engaged in their turnover within the P cycle.

Phosphonates are organophosphorus metabolites with a characteristic C-P bond. They are ubiquitous in the marine environment, their degradation broadly supports ecosystem productivity, and they are key components of the marine phosphorus (P) cycle. However, the microbial producers that sustain the large oceanic inventory of phosphonates as well as the physiological and ecological roles of phosphonates are enigmatic. Here, we show that phosphonate synthesis genes are rare but widely distributed among diverse bacteria and archaea, including Prochlorococcus and SAR11, the two major groups of bacteria in the ocean. In addition, we show that Prochlorococcus can allocate over 40% of its total cellular P-quota toward phosphonate production. However, we find no evidence that Prochlorococcus uses phosphonates for surplus P storage, and nearly all producer genomes lack the genes necessary to degrade and assimilate phosphonates. Instead, we postulate that phosphonates are associated with cell-surface glycoproteins, suggesting that phosphonates mediate ecological interactions between the cell and its surrounding environment. Our findings indicate that the oligotrophic surface ocean phosphonate pool is sustained by a relatively small fraction of the bacterioplankton cells allocating a significant portion of their P quotas toward secondary metabolism and away from growth and reproduction.

Glyphosate is currently one of the most important herbicides worldwide. Its unique properties provide for a wide range of uses in agriculture but also in non-agricultural areas. At the same time, its zwitterionic nature prevents the inclusion in multi-residue analytical methods for environmental monitoring. Consequently, despite its extensive use, data on occurrence of glyphosate in the aquatic environment is still scarce. Based on existing methods, we developed a simplified procedure for the determination of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in water samples using derivatization with fluorenylmethyl chloroformate FMOC-Cl, combined with on-line solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. This method was extensively tested on over 1000 samples of surface water, groundwater, and treated wastewater and proved to be simple, sensitive, and reliable. Limits of quantification of 0.005 μg/L were routinely achieved. Glyphosate and AMPA were detected in the vast majority of stream water samples in the area of Zurich, Switzerland, with median concentrations of 0.11 and 0.20 μg/L and 95th percentile concentrations of 2.1 and 2.6 μg/L, respectively. Stream water data and data from treated wastewater indicated that non-agricultural uses may significantly contribute to the overall loads of glyphosate and AMPA in surface waters. In the investigated groundwater samples, selected specifically because they had shown presence of other herbicides in previous monitoring programs, glyphosate and AMPA were generally not detected, except for two monitoring sites in Karst aquifers, indicating that these compounds show much less tendency for leaching.

Considerable attention is given to absolute nutrient levels in lakes, rivers, and oceans, but less is paid to their relative concentrations, their nitrogen:phosphorus (N:P) stoichiometry, and the consequences of imbalanced stoichiometry. Here, we report 38 y of nutrient dynamics in Flathead Lake, a large oligotrophic lake in Montana, and its inflows. While nutrient levels were low, the lake had sustained high total N: total P ratios (TN:TP: 60 to 90:1 molar) throughout the observation period. N and P loading to the lake as well as loading N:P ratios varied considerably among years but showed no systematic long-term trend. Surprisingly, TN:TP ratios in river inflows were consistently lower than in the lake, suggesting that forms of P in riverine loading are removed preferentially to N. In-lake processes, such as differential sedimentation of P relative to N or accumulation of fixed N in excess of denitrification, likely also operate to maintain the lake’s high TN:TP ratios. Regardless of causes, the lake’s stoichiometric imbalance is manifested in P limitation of phytoplankton growth during early and midsummer, resulting in high C:P and N:P ratios in suspended particulate matter that propagate P limitation to zooplankton. Finally, the lake’s imbalanced N:P stoichiometry appears to raise the potential for aerobic methane production via metabolism of phosphonate compounds by P-limited microbes. These data highlight the importance of not only absolute N and P levels in aquatic ecosystems, but also their stoichiometric balance, and they call attention to potential management implications of high N:P ratios.

[...] there is improved clarity about the threshold concentration of tenofovir that is likely to protect against HIV, the goal in future clinical trials of this drug should be to attain the highest tolerable drug concentrations in the vagina. [...] new PrEP formulations, such as intravaginal rings and injectables, will need to be carefully assessed to work out whether the drug concentrations achieved at the site of viral exposure are likely to be high enough to prevent HIV infection.

Marine microbial communities rely on dissolved organic phosphorus (DOP) remineralisation to meet phosphorus (P) requirements. We extensively surveyed the genomic and metagenomic distribution of genes directing phosphonate biosynthesis, substrate-specific catabolism of 2-aminoethylphosphonate (2-AEP, the most abundant phosphonate in the marine environment), and broad-specificity catabolism of phosphonates by the C-P lyase (including methylphosphonate, a major source of methane). We developed comprehensive enzyme databases by curating publicly available sequences and then screened metagenomes from TARA Oceans and Munida Microbial Observatory Time Series (MOTS) to assess spatial and seasonal variation in phosphonate metabolism pathways. Phosphonate cycling genes were encoded in diverse gene clusters by 35 marine bacterial and archaeal classes. More than 65% of marine phosphonate cycling genes mapped to Proteobacteria with production demonstrating wider taxonomic diversity than catabolism. Hydrolysis of 2-AEP was the dominant phosphonate catabolism strategy, enabling microbes to assimilate carbon and nitrogen alongside P. Genes for broad-specificity catabolism by the C-P lyase were far less widespread, though enriched in the extremely P-deplete environment of the Mediterranean Sea. Phosphonate cycling genes were abundant in marine metagenomes, particularly from the mesopelagic zone and winter sampling dates. Disparity between prevalence of substrate-specific and broad-specificity catabolism may be due to higher resource expenditure from the cell to build and retain the C-P lyase. This study is the most comprehensive metagenomic survey of marine microbial phosphonate cycling to date and provides curated databases for 14 genes involved in phosphonate cycling.

Four bacterial strains from glyphosate- or alkylphosphonates-contaminated soils were tested for ability to utilize different organophosphonates. All studied strains readily utilized methylphosphonic acid and a number of other phosphonates, but differed in their ability to degrade glyphosate. Only strains Ochrobactrum anthropi GPK 3 and Achromobacter sp. Kg 16 utilized this compound after isolation from enrichment cultures with glyphosate. Achromobacter sp. MPK 7 from the same enrichment culture, similar to Achromobacter sp. MPS 12 from methylphosphonate-polluted source, required adaptation to growth on GP. Studied strains varied significantly in their growth parameters, efficiency of phosphonates degradation and characteristic products of this process, as well as in their energy metabolism. These differences give grounds to propose a possible model of interaction between these strains in microbial consortium in phosphonate-contaminated soils.

The metabolic stress-sensing enzyme AMP-activated protein kinase (AMPK) is responsible for regulating metabolism in response to energy supply and demand. Drugs that activate AMPK may be useful in the treatment of metabolic diseases including type 2 diabetes. We have determined the crystal structure of AMPK in complex with its activator 5-(5-hydroxyl-isoxazol-3-yl)-furan-2-phosphonic acid (C2), revealing two C2-binding sites in the γ-subunit distinct from nucleotide sites. C2 acts synergistically with the drug A769662 to activate AMPK α1-containing complexes independent of upstream kinases. Our results show that dual drug therapies could be effective AMPK-targeting strategies to treat metabolic diseases. AMPK regulates the metabolism and so drugs that activate AMPK might have potential for the treatment of metabolic disease. Here, the authors report the structure of AMPK bound to an activating compound, revealing two binding sites and indicating that dual therapy might be a good drug strategy.

In Escherichia coli , the 14-cistron phn operon encoding carbon-phosphorus lyase allows for utilisation of phosphorus from a wide range of stable phosphonate compounds containing a C-P bond. As part of a complex, multi-step pathway, the PhnJ subunit was shown to cleave the C-P bond via a radical mechanism, however, the details of the reaction could not immediately be reconciled with the crystal structure of a 220 kDa PhnGHIJ C-P lyase core complex, leaving a significant gap in our understanding of phosphonate breakdown in bacteria. Here, we show using single-particle cryogenic electron microscopy that PhnJ mediates binding of a double dimer of the ATP-binding cassette proteins, PhnK and PhnL, to the core complex. ATP hydrolysis induces drastic structural remodelling leading to opening of the core complex and reconfiguration of a metal-binding and putative active site located at the interface between the PhnI and PhnJ subunits. Here, authors analyse the structural organisation of the large carbon-phosphorus lyase enzyme from bacteria using electron microscopy and discover that it contains two ATP-binding cassette dimers of PhnK and PhnL and opens upon ATP hydrolysis.