Controlled motility in the cyanobacterium Trichodesmium regulates aggregate architecture

in Science (2023), 380(6647), 830-835

The ocean’s nitrogen is largely fixed by cyanobacteria, including Trichodesmium, which forms aggregates comprising hundreds of filaments arranged in organized architectures. Aggregates often form upon ... [more ▼]

The ocean’s nitrogen is largely fixed by cyanobacteria, including Trichodesmium, which forms aggregates comprising hundreds of filaments arranged in organized architectures. Aggregates often form upon exposure to stress and have ecological and biophysical characteristics that differ from those of single filaments. Here, we report that Trichodesmium aggregates can rapidly modulate their shape, responding within minutes to changes in environmental conditions. Combining video microscopy and mathematical modeling, we discovered that this reorganization is mediated by “smart reversals” wherein gliding filaments reverse when their overlap with other filaments diminishes. By regulating smart reversals, filaments control aggregate architecture without central coordination. We propose that the modulation of gliding motility at the single-filament level is a determinant of Trichodesmium’s aggregation behavior and ultimately of its biogeochemical role in the ocean. [less ▲]

The exposome and health: Where chemistry meets biology

in Science (2020), 367(6476), 392--396

Despite extensive evidence showing that exposure to specific chemicals can lead to disease, current research approaches and regulatory policies fail to address the chemical complexity of our world. To ... [more ▼]

Despite extensive evidence showing that exposure to specific chemicals can lead to disease, current research approaches and regulatory policies fail to address the chemical complexity of our world. To safeguard current and future generations from the increasing number of chemicals polluting our environment, a systematic and agnostic approach is needed. The \textquotedblleftexposome\textquotedblright concept strives to capture the diversity and range of exposures to synthetic chemicals, dietary constituents, psychosocial stressors, and physical factors, as well as their corresponding biological responses. Technological advances such as high-resolution mass spectrometry and network science have allowed us to take the first steps toward a comprehensive assessment of the exposome. Given the increased recognition of the dominant role that nongenetic factors play in disease, an effort to characterize the exposome at a scale comparable to that of the human genome is warranted. [less ▲]

Wavelike charge density fluctuations and van der Waals interactions at the nanoscale

in Science (2016), 351(6278), 1171-1176

Recent experiments on noncovalent interactions at the nanoscale have challenged the basic assumptions of commonly used particle- or fragment-based models for describing van der Waals (vdW) or dispersion ... [more ▼]

Recent experiments on noncovalent interactions at the nanoscale have challenged the basic assumptions of commonly used particle- or fragment-based models for describing van der Waals (vdW) or dispersion forces. We demonstrate that a qualitatively correct description of the vdW interactions between polarizable nanostructures over a wide range of finite distances can only be attained by accounting for the wavelike nature of charge density fluctuations. By considering a diverse set of materials and biological systems with markedly different dimensionalities, topologies, and polarizabilities, we find a visible enhancement in the nonlocality of the charge density response in the range of 10 to 20 nanometers. These collective wavelike fluctuations are responsible for the emergence of nontrivial modifications of the power laws that govern noncovalent interactions at the nanoscale. [less ▲]

Reproducibility in density functional theory calculations of solids

in Science (2016), 351

PINK1 loss-of-function mutations affect mitochondrial complex I activity via NdufA10 ubiquinone uncoupling.

in Science (2014), 344(6180), 203-7

Under resting conditions, Pink1 knockout cells and cells derived from patients with PINK1 mutations display a loss of mitochondrial complex I reductive activity, causing a decrease in the mitochondrial ... [more ▼]

Under resting conditions, Pink1 knockout cells and cells derived from patients with PINK1 mutations display a loss of mitochondrial complex I reductive activity, causing a decrease in the mitochondrial membrane potential. Analyzing the phosphoproteome of complex I in liver and brain from Pink1(-/-) mice, we found specific loss of phosphorylation of serine-250 in complex I subunit NdufA10. Phosphorylation of serine-250 was needed for ubiquinone reduction by complex I. Phosphomimetic NdufA10 reversed Pink1 deficits in mouse knockout cells and rescued mitochondrial depolarization and synaptic transmission defects in pink(B9)-null mutant Drosophila. Complex I deficits and adenosine triphosphate synthesis were also rescued in cells derived from PINK1 patients. Thus, this evolutionary conserved pathway may contribute to the pathogenic cascade that eventually leads to Parkinson's disease in patients with PINK1 mutations. [less ▲]

Three-dimensional structural view of the central metabolic network of Thermotoga maritima.

in Science (2009), 325(5947), 1544-1549

Metabolic pathways have traditionally been described in terms of biochemical reactions and metabolites. With the use of structural genomics and systems biology, we generated a three-dimensional ... [more ▼]

Metabolic pathways have traditionally been described in terms of biochemical reactions and metabolites. With the use of structural genomics and systems biology, we generated a three-dimensional reconstruction of the central metabolic network of the bacterium Thermotoga maritima. The network encompassed 478 proteins, of which 120 were determined by experiment and 358 were modeled. Structural analysis revealed that proteins forming the network are dominated by a small number (only 182) of basic shapes (folds) performing diverse but mostly related functions. Most of these folds are already present in the essential core (approximately 30%) of the network, and its expansion by nonessential proteins is achieved with relatively few additional folds. Thus, integration of structural data with networks analysis generates insight into the function, mechanism, and evolution of biological networks. [less ▲]

Changes in surface water supply across Africa with predicted climate change

in Science (2006), 311(5769), 1917-1921

Across Africa, perennial drainage density as a function of mean annual rainfall defines three regimes separated by threshold values of precipitation. This nonlinear response of drainage to rainfall will ... [more ▼]

Across Africa, perennial drainage density as a function of mean annual rainfall defines three regimes separated by threshold values of precipitation. This nonlinear response of drainage to rainfall will most seriously affect regions in the intermediate, unstable regime. A 10% decrease in precipitation in regions on the upper regime boundary (1000 millimeters per year) would reduce drainage by 17%, whereas in regions receiving 500 millimeters per year, such a drop would cut 50% of surface drainage. By using predicted precipitation changes, we calculate that a decrease in perennial drainage will significantly affect present surface water access across 25% of Africa by the end of this century. [less ▲]

Sequence interpretation. Functional annotation of mouse genome sequences.

in Science (2001), 291(5507), 1251-5