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Unpacking drivers of heterotrophic N2 fixation across aquatic redox gradients: A mathematical model with bioenergetic and stoichiometric constraints
No full textN2 fixation by aquatic organoheterotrophs supplies bioavailable nitrogen to the biosphere and thereby supports ecosystem production; yet the factors which drive this activity are poorly understood. Here, we present a generalized chemostat model to investigate stoichiometric and energetic constraints on free-living heterotrophic diazotrophs across gradients in redox state, resource quantity/quality, and resource stoichiometry. The model couples nutrient uptake and allocation functions to predict elemental fluxes with an energy dissipation model to calculate growth efficiency. After constraining model parameters with relevant culturing (e.g., Azotobacter) and environmental literature, we assessed model sensitivity to these parameters using Latin Hypercube Sampling and the statistical Partial Rank Correlation Coefficient technique. Consistent with the limited observational data available, the results showed energy acquisition and respiratory efficiency as two major controls on N2 fixation. The model predicted the presence of N2 fixation under both N-limiting and N-replete conditions, as seen in nature. N2 fixation under N-replete conditions increased with increasing resource C:N, and was least sensitive to exogenous N under eutrophic conditions with an energy-rich C source. While N2 fixation under N-replete conditions represented a relatively small (\u3c4 %) contribution to community N demand, absolute rates under these conditions were on par with field observations under N-limitation due to higher overall heterotrophic production rates. Resolving physiological, stoichiometric, and energetic constraints on diazotrophic growth, this model unpacks drivers of N2 fixation by metabolically diverse heterotrophs
Musico Stilo: Aspects of the Poetry of Ennodius [book review]
No full textFranca Ela Consolino: Musico stilo. Aspects of the Poetry of Ennodius. Turnhout: Brepols 2024 (Studi e testi tardoantichi 24). 309 p., 4 tables. € 80.00. ISBN: 978-2-503-61112-9
Collateral damages: Tracing the debts and displacements of the Iraq War [book review]
No full textCollateral damages: Tracing the debts and displacements of the Iraq War By Nadia El-Shaarawi, Oakland: University of California Press. 2025. 239 pp
La última guerra del Siglo de las Luces: Revolución Liberal y republicanismo popular en Ecuador [book review]
No full textLa última guerra del Siglo de las Luces: Revolución Liberal y republicanismo popular en Ecuador. By Valeria Coronel. Serie Atrio. Quito: Editorial FLACSO Ecuador, 2022. Photographs. Figure. Notes. Bibliography. xiv, 417 pp. Paper
Five-In-One Antibacterial Strategy: A Mn(I) Complex Lights Up the Fight Against Tuberculosis
No full textTuberculosis, which the WHO describes as the “world\u27s top infectious killer,” demands novel combating strategies rather than conventional ones, as the situation of Mycobacterium tuberculosis (Mtb) resistance to therapeutic drugs is continuous, leading to millions of deaths each year. In a recent study, Lai et al. report a manganese(I)-based photoactivatable carbon monoxide-releasing molecule (Mn-PTP) that unifies photodynamic therapy, transition metal reactivity, and carbon monoxide (CO) delivery into a single light-activated therapeutic platform. Upon white-light irradiation, Mn-PTP releases CO, generates both type I and type II reactive oxygen species (ROS), liberates a toxic antibacterial ligand (PTP), and forms catalytically active manganese oxides (MnOx) species that decompose intracellular hydrogen peroxide (H2O2), thereby alleviating hypoxia and amplifying ROS generation. Mn-PTP demonstrates high selectivity for Mycobacterium smegmatis with, potent in vitro antibacterial activity (MIC90 = 3.11 μM), robust biofilm disruption of M. smegmatis, and minimal cytotoxicity to normal cells. In in vivo, the compound significantly accelerates wound healing in infected mice, outperforming isoniazid. This highlight discusses Mn-PTP as a powerful “one-for-all” agent which, upon irradiation, releases five key components that, much like the five fingers through coordinated action, form a fist that effectively combats and eliminates bacterial infections, offering a powerful blueprint for next-generation metal-based therapeutics against persistent mycobacterial infections
