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1. Potential Phosphorus Uptake Mechanisms in the Deep Sedimentary Biosphere

   https://doi.org/10.3389/fmars.2022.907527  

   Defforey, Delphine; Tully, Benjamin J.; Sylvan, Jason B.; Cade-Menun, Barbara J.; Kiel Reese, Brandi; Zinke, Laura; Paytan, Adina (June 2022, Frontiers in Marine Science)

   Our understanding of phosphorus (P) dynamics in the deep subseafloor environment remains limited. Here we investigate potential microbial P uptake mechanisms in oligotrophic marine sediments beneath the North Atlantic Gyre and their effects on the relative distribution of organic P compounds as a function of burial depth and changing redox conditions. We use metagenomic analyses to determine the presence of microbial functional genes pertaining to P uptake and metabolism, and solution 31 P nuclear magnetic resonance spectroscopy ( 31 P NMR) to characterize and quantify P substrates. Phosphorus compounds or compound classes identified with 31 P NMR include inorganic P compounds (orthophosphate, pyrophosphate, polyphosphate), phosphonates, orthophosphate monoesters (including inositol hexakisphosphate stereoisomers) and orthophosphate diesters (including DNA and phospholipid degradation products). Some of the genes identified include genes related to phosphate transport, phosphonate and polyphosphate metabolism, as well as phosphite uptake. Our findings suggest that the deep sedimentary biosphere may have adapted to take advantage of a wide array of P substrates and could play a role in the gradual breakdown of inositol and sugar phosphates, as well as reduced P compounds and polyphosphates. 

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2. Two-sided effects of the organic phosphorus phytate on a globally important marine coccolithophorid phytoplankton

   https://doi.org/10.1128/spectrum.01255-23  

   Li, Jiashun; Zhang, Kaidian; Li, Ling; Wang, Yujie; Wang, Cong; Lin, Senjie (October 2023, Microbiology Spectrum)

   Re, Angela (Ed.)

   ABSTRACT Dissolved organic phosphorus (DOP) is a potential source of aquatic eutrophication and pollution because it can potentially stimulate growth in some species and inhibit growth in other species of algae, the foundation of the marine ecosystem. Inositol hexaphosphate (also named phytic acid or PA), an abundant organophosphate, is presumably ubiquitous in the marine environment, but how it affects marine primary producers is poorly understood. Here, we investigated the bioavailability of this DOP to the cosmopolitan coccolithophoreEmiliania huxleyi. Our results showed thatE.huxleyicells can take up PA and dissolved inorganic phosphorus (DIP) simultaneously. Absorbed PA can efficiently support algal growth, producing cell yield between DIP and phosphorus (P)-depleted conditions. Accordingly, PA supply as the sole P source highly influences cellular metabolism and nutrient stoichiometry. Particularly, PA-grown cultures exhibited enhanced carbon fixation, increased lipid content, activated energy metabolism, and induced nitrogen assimilation. However, our data suggest that PA may also exert some levels of toxic effects onE. huxleyi. This study provides novel insights into the variable effects of a DOP on marine phytoplankton, which will inform new inquiries about how the complex DOP constituencies in the ocean will shape phytoplankton community structure and function. IMPORTANCEThe dissolved organic phosphorus (DOP) utilization in phytoplankton plays vital roles in cellular P homeostasis, P-nutrient niche, and the dynamics of community structure in marine ecosystems, but its mechanisms, potentially varying with species, are far from clear. In this study, we investigated the utilization of a widespread DOP species, which is commonly produced by plants (land plants and marine macrophytes) and released into coastal areas, in a globally distributed bloom-forming coccolithophore species in various phosphorus environments. Using a combination of physiological and transcriptomic measurements and analyses, our experimental results revealed the complex mechanism and two-sided effects of DOP (major algal growth-supporting and minor toxic effects) in this species, providing a novel perspective on phytoplankton nutrient regulation. 

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3. Trading acyls and swapping sugars: metabolic innovations in Solanum trichomes

   https://doi.org/10.1093/plphys/kiae279  

   Fiesel, Paul_D; Kerwin, Rachel_E; Jones, A_Daniel; Last, Robert_L (May 2024, Plant Physiology)

   Abstract Solanaceae (nightshade family) species synthesize a remarkable array of clade- and tissue-specific specialized metabolites. Protective acylsugars, one such class of structurally diverse metabolites, are produced by ACYLSUGAR ACYLTRANSFERASE (ASAT) enzymes from sugars and acyl-coenzyme A esters. Published research has revealed trichome acylsugars composed of glucose and sucrose cores in species across the family. In addition, acylsugars have been analyzed across a small fraction of the >1,200 species in the phenotypically megadiverse Solanum genus, with a handful containing inositol and glycosylated inositol cores. The current study sampled several dozen species across subclades of Solanum to get a more detailed view of acylsugar chemodiversity. In depth characterization of acylsugars from the clade II species brinjal eggplant (Solanum melongena) led to the identification of eight unusual structures with inositol or inositol glycoside cores and hydroxyacyl chains. Liquid chromatography-mass spectrometry analysis of 31 additional species in the Solanum genus revealed striking acylsugar diversity, with some traits restricted to specific clades and species. Acylinositols and inositol-based acyldisaccharides were detected throughout much of the genus. In contrast, acylglucoses and acylsucroses were more restricted in distribution. Analysis of tissue-specific transcriptomes and interspecific acylsugar acetylation differences led to the identification of the brinjal eggplant ASAT 3-LIKE 1 (SmASAT3-L1; SMEL4.1_12g015780) enzyme. This enzyme is distinct from previously characterized acylsugar acetyltransferases, which are in the ASAT4 clade, and appears to be a functionally divergent ASAT3. This study provides a foundation for investigating the evolution and function of diverse Solanum acylsugar structures and harnessing this diversity in breeding and synthetic biology. 

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4. A Global Survey of Hypervirulent Aeromonas hydrophila (vAh) Identified vAh Strains in the Lower Mekong River Basin and Diverse Opportunistic Pathogens from Farmed Fish and Other Environmental Sources

   https://doi.org/10.1128/spectrum.03705-22  

   Xu, Tingbi; Rasmussen-Ivey, Cody R.; Moen, Francesco S.; Fernández-Bravo, Ana; Lamy, Brigitte; Beaz-Hidalgo, Roxana; Khan, Chan Dara; Castro Escarpulli, Graciela; Yasin, Ina Salwany; Figueras, Maria J.; et al (April 2023, Microbiology Spectrum)

   Iwanowicz, Luke R. (Ed.)

   ABSTRACT Hypervirulent Aeromonas hydrophila (vAh) has emerged as the etiologic agent of epidemic outbreaks of motile Aeromonas septicemia (MAS) in high-density aquaculture of farmed carp in China and catfish in the United States, which has caused millions of tons of lost fish. We conducted a global survey to better understand the evolution, geographical distribution, and phylogeny of vAh. Aeromonas isolates were isolated from fish that showed clinical symptoms of MAS, and pure cultures were screened for the ability to utilize myo -inositol as the sole carbon source. A total of 113 myo- inositol-utilizing bacterial strains were included in this study, including additional strains obtained from previously published culture collections. Based on a gyrB phylogeny, this collection included 66 A. hydrophila isolates, 48 of which were vAh. This collection also included five new vAh isolates from diseased Pangas catfish ( Pangasius pangasius ) and striped catfish ( Pangasianodon hypophthalmus ) obtained in Cambodia and Vietnam, respectively. Genome sequences were generated from representative vAh and non-vAh isolates to evaluate the potential for lateral genetic transfer of the myo- inositol catabolism pathway. Phylogenetic analyses of each of the nine genes required for myo -inositol utilization revealed the close affiliation of vAh strains regardless of geographic origin and suggested lateral genetic transfer of this catabolic pathway from an Enterobacter species. Prediction of virulence factors was conducted to determine differences between vAh and non-vAh strains in terms of virulence and secretion systems. Core genome phylogenetic analyses on vAh isolates and Aeromonas spp. disease isolates (55 in total) were conducted to evaluate the evolutionary relationships among vAh and other Aeromonas sp. isolates, which supported the clonal nature of vAh isolates. IMPORTANCE This global survey of vAh brought together scientists that study fish disease to evaluate the evolution, geographical distribution, phylogeny, and hosts of vAh and other Aeromonas sp. isolates. In addition to vAh isolates from China and the United States, four new vAh isolates were isolated from the lower Mekong River basin in Cambodia and Vietnam, indicating the significant threat of vAh to modern aquaculture and the need for improved biosecurity to prevent vAh spread. 

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5. Adsorption and precipitation of myo ‐inositol hexakisphosphate onto kaolinite

   https://doi.org/10.1111/ejss.12849  

   Hu, Zhen; Jaisi, Deb_P; Yan, Yupeng; Chen, Hongfeng; Wang, Xiaoming; Wan, Biao; Liu, Fan; Tan, Wenfeng; Huang, Qiaoyun; Feng, Xionghan (July 2019, European Journal of Soil Science)

   Abstract Sorption ofmyo‐inositol hexakisphosphate (IHP), a common type of organic phosphorus in soils, largely controls its mobility and bioavailability. Research on the interaction between IHP and phyllosilicate minerals such as kaolinite, which is commonly present in highly weathered soils, has often been neglected, probably due to the common assumption that negatively charged phyllosilicate minerals have low sorption capacity and binding affinity to IHP and thus do not play any significant role in its fate. Here, the interaction between IHP and poorly crystallized kaolinite (KGa‐2) was investigated in batch experiments using Zeta (ζ) potential measurement and³¹P nuclear magnetic resonance (NMR) spectroscopy. The results showed that dissolved Al(III) concentration at the adsorption initiation stage increased with increasing IHP concentration at pH 4.0. From pH 2.5 to 9.0, IHP presented a maximum sorption capacity (50 μmol g⁻¹) at pH 4.0 at 24 hr. With IHP sorption, theζpotential of kaolinite first decreased sharply to a negative value, then gradually increased with resorption of Al(III) released from kaolinite dissolution at acidic pH, and finally approached the original value of the pure kaolinite.³¹P NMR spectroscopy andζpotential analyses revealed that IHP formed inner‐sphere surface complexes and aluminium phytate precipitated on kaolinite at low pH (2.5 and 4.0), whereas the formation of inner‐sphere surface complexes was the dominant sorption mechanism at pH ≥ 5.5. This study implies that various mechanisms, depending on ambient pH condition, can dominate the IHP sorption onto kaolinite, which impacts the mobility and bioavailability of phosphorus in highly weathered soils. HighlightsIHP promotes the dissolution of kaolinite mainly through the formation of aluminium phytate complex.IHP sorption presents a sharp maximum at pH 4.0.IHP forms inner‐sphere complexes at the surface of kaolinite.Formation of aluminium phytate surface precipitates is favourable at relatively low pH. 

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