Guanidine fuels rapid resurrection of desert cyanobacteria.

July 28, 2026| Source: Proceedings of the National Academy of Sciences of the United States of America

In desert ecosystems, microbial activity is driven by brief hydration pulses but is severely limited by persistent nutrient scarcity. Cyanobacteria serve as essential pioneer photoautotrophs, maintaining biogeochemical cycles and ecosystem stability in these arid landscapes. However, their ability to quickly reactivate after rehydration is critically restricted by nitrogen availability. Although the nitrogen demand can be met later by biological nitrogen fixation, it is ineffective and irrelevant during early rehydration due to the high energy costs and delayed activation of nitrogenase, creating a critical metabolic bottleneck. Here we demonstrate that the desert cyanobacterium Nostoc flagelliforme overcomes this limitation by activating a previously overlooked guanidine carboxylase pathway, which sustains the rapid remobilization of internal nitrogen reserves upon rehydration. Transcriptional analysis using a luciferase reporter system reveals that pathway activity is tightly coupled to both hydration and nitrogen status. Disruption of the guanidine-specific riboswitch abolishes induction of the guanidine carboxylase pathway, underscoring its essential role in recovery from desiccation. Furthermore, comparative genomics reveals that the genes encoding this pathway, along with its cognate riboswitch, are widespread among terrestrial cyanobacteria. Phylogenetic analysis indicates they were acquired via horizontal gene transfer from nonphotosynthetic bacteria. Our findings establish an ecological role for guanidine in desert ecosystems and uncover a conserved mechanism that aids cyanobacterial resilience in xeric environments.

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Reversing vegetable biodiversity loss to diversify diets.

Vegetables are a critical component of diets, with inadequate intake of this essential food group leading to poor dietary quality and malnutrition. Food system assessments identify insufficient production, comparatively high prices, and sociocultural barriers as key constraints to vegetable consumption. We argue that vegetable biodiversity, spanning vegetable species and their varieties, as well as their wild relative species, is a central yet underutilized lever for enhancing vegetable consumpt

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Sediment accumulation rate predicts the temporal resolution of marine fossil assemblages.

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EnvironmentJuly 28, 2026

Geometry controls momentum flux in the sprinkler problem.

Hydro- and aero-mechanical devices convert fluid flows into useful motions, force, and power. The operating principles can involve subtle and poorly understood physics, as epitomized by open questions about systems that aspirate flows through curving tubular arms. Since its introduction by Mach and popularization by Feynman, the so-called reverse sprinkler problem has evoked many competing theories and fluid mechanical effects that have not to date been distinguished by experiments. Here we cond

EnvironmentJuly 28, 2026

The unique Efg1 fungal virulence regulon in the catheterized bladder environment.

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EnvironmentJuly 28, 2026

A unified machine-learning framework for ab initio multiscale modeling of liquids.

Understanding and predicting the behavior of liquid matter across length scales-using only the microscopic interactions encoded in the Schrödinger equation-remains a central challenge in the physical sciences. Achieving this goal requires not only an accurate and efficient description of intermolecular forces but also a consistent framework that bridges the micro-, meso-, and macroscales. Here, by combining machine-learned interatomic potentials (MLIPs) with neural classical density functio