Center for Marine Biodiversity and Conservation

Although the green revolution adapted a handful of crops to homogeneous and high-input industrialized agriculture, much of the global population still relies on the local production of variable crop cultivars by low-input smallholder farms. This diversity of unhomogenized crops1, like that of the grain and bioenergy crop sorghum2, 3, 4–5, offers raw materials for genetic gain and cultivar improvement. However, breeding efforts can be constrained by highly specialized traits and breeding targets6. Here, to bridge this diversity, we constructed a 33-member pangenome reference and a diversity panel across 1,984 cultivars and landraces. We leveraged these resources to explore the complex interplay among historical contingency, ongoing adaptation and previously uncharacterized structural diversity. Specifically, our analyses conclusively demonstrated multiple nested and deeply diverged structural variants in the domestication gene SHATTERING1, which distinguish the previously established multicentric origin of sorghum. We then applied landscape genomics to reveal how gene flow and secondary contact created the complex genetic mosaic in contemporary breeding networks. As proof of concept for pangenome-accelerated trait discovery, we connected biosynthetic gene cluster structural variation to phenotypic leaf concentration of the cyanogenic glucoside dhurrin. Combined, these approaches will accelerate breeding and trait discovery and provide a framework for similar applications in other crops.

Cyanobacteria are prolific producers of biologically active compounds that are important in influencing ecology, behavior of interacting organisms, and as leads in drug discovery efforts. Here we discuss the challenges faced by all natural product researchers, especially those that focus on cyanobacteria, and then describe progress that has been made in these areas. We also propose some solutions, paths forward, and thoughts for consideration on these challenges.

The interdisciplinary nature of microbiome research, coupled with the generation of complex multi-omics data, makes knowledge sharing challenging. The Strengthening the Organization and Reporting of Microbiome Studies (STORMS) guidelines provide a checklist for the reporting of study information, experimental design and analytical methods within a scientific manuscript on human microbiome research. Here, in this Consensus Statement, we present the standards for technical reporting in environmental and host-associated microbiome studies (STREAMS) guidelines. The guidelines expand on STORMS and include 67 items to support the reporting and review of environmental (for example, terrestrial, aquatic, atmospheric and engineered), synthetic and non-human host-associated microbiome studies in a standardized and machine-actionable manner. Based on input from 248 researchers spanning 28 countries, we provide detailed guidance, including comparisons with STORMS, and case studies that demonstrate the usage of the STREAMS guidelines. STREAMS, like STORMS, will be a living community resource updated by the Consortium with consensus-building input of the broader community.

The detrimental effects on human health sometimes observed during blooms of Lingulaulax polyedra have been formerly attributed to the yessotoxin analogs this species produces. In this paper we show that natural concentrations of yessotoxin analogs present in seawater and sea spray aerosols during an unprecedented L. polyedra bloom in 2020 in Southern California did not induce inflammation in mammal macrophage cells, questioning the role played by yessotoxin in causing respiratory irritations. This bloom was associated with unprecedented levels of particulate dimethylsulfoniopropionate (2.74 ± 1.63 to 10.11 ± 1.39 µM), gonyol and several new structural analogs ofgonyol . We profiled the metabolic content of dinoflagellate cells and recorded increasing amounts of quaternary amines of the betaine family (carnitine, actinin, ectoine) as the bloom progressed. Being precursors of sulfur and nitrogenous small volatile compounds, we hypothesize that, in addition to their recognized role in climate processes, these sulfur and nitrogenous osmolytes may also play a key role in health-related issues reported during intense L. polyedra blooms.

Kahalalide F is a cyclic depsipeptide with notable anticancer properties, initially discovered from the green alga Bryopsis sp. and its molluscan predator Elysia rufescens. Recent studies have pinpointed a bacterial endosymbiont of the green alga, Candidatus Endobryopsis kahalalidefaciens, as the true producer of kahalalide F. In the present work, we characterize a closely related kahalalide F analog, kahalalide Z₅, from the marine cyanobacterium Limnoraphis sp. collected in the Las Perlas Islands, Panama, and propose the structures of several related compounds by detailed MS analysis. To uncover novel metabolites and prioritize them for targeted isolation from this organism, we employed a robust metabolomics strategy combining LC-MS/MS with SMART NMR and DeepSAT, artificial intelligence platforms trained to infer chemical structures from ¹H-¹³C HSQC NMR data. This integrated approach annotated a compound with structural similarities to kahalalide F, which we subsequently characterized using a suite of spectroscopic techniques and chemical degradation studies. Whole-genome sequencing of the producing strain further revealed a NRPS biosynthetic gene cluster that aligns with the structural features of kahalalide Z₅. This study identifies the marine cyanobacterium Limnoraphis sp. as an independent source of kahalalide F-like molecules. This work broadens the phylogenetic spectrum of organisms capable of producing these bioactive compounds, reveals marine cyanobacteria as producers of an increased repertoire of unique natural products, and illustrates the potential of AI-enhanced metabolomic and genomic analyses to streamline the discovery and characterization of complex biomedically relevant natural products.

The spatial structure and dynamics of populations are important considerations when defining management units in organisms that are harvested as natural resources. In the Eastern Pacific, Pacific Sardine range from Chile to Alaska, the northernmost state of the United States (U.S.), and once supported an expansive and productive fishery. Along its North American range, it is hypothesized to comprise three subpopulations: a northern and southern subpopulation, which primarily occur off the coast of the U.S. and Baja California, Mexico (M.X.), respectively, and a third in the Gulf of California, M.X. We used low coverage whole genome sequencing to generate genotype likelihoods for millions of SNPs in 317 individuals collected from the Gulf of California, M.X., to Oregon, U.S., to assess population structure in Pacific Sardine. Differentiation across the genome was driven by variation at several putative chromosomal inversions ranging in size from ~21 MB to 0.89 MB, although none of the putative inversions showed any evidence of geographic differentiation. Our results support panmixia across an impressive ~4000 km range.

Decaying barrels on the seafloor linked to DDT contamination have raised concerns about the public health implications of decades old industrial waste dumped off the coast of Los Angeles. To explore their contents, we collected sediment cores perpendicular to five deep-sea barrels. The concentration of DDT and its breakdown products were highly elevated relative to control sites yet did not vary with distance from the barrels, suggesting that they were not associated with the contamination. Sediment cores collected through white halos surrounding three barrels were enriched in calcite and had elevated pH. The associated microbial communities were low diversity and dominated by alkalophilic bacteria with metagenome-assembled genomes adapted to high pH. A solid concretion sampled between a white halo and barrel was composed of brucite, a magnesium hydroxide mineral that forms at high pH. Based on these findings, we postulate that leakage of containerized alkaline waste triggered the formation of mineral concretions that are slowly dissolving and raising the pH of the surrounding sediment pore water. This selects for taxa adapted to extreme alkalinity and drives the precipitation of "anthropogenic" carbonates forming white halos, which serve as a visual identifier of barrels that contained alkaline waste. Remarkably, containerized alkaline waste discarded >50 years ago represents a persistent pollutant creating localized mineral formations and microbial communities that resemble those observed at some hydrothermal systems. These formations were observed at one-third of the visually identified barrels in the San Pedro Basin and have unforeseen, long-term consequences for benthic communities in the region.

Halogenated indole natural products have been isolated from a variety of organisms, including plants, marine algae, marine invertebrates, and bacteria. Aquatic cyanobacteria, in particular, are rich producers of brominated indoles, but their cognate biosynthetic enzymes have only been successfully linked in a limited number of natural products, such as the eagle-killing toxin aetokthonotoxin (AETX). The biosynthetic pathway for AETX involves five enzymes, two of which were previously undescribed due to incomplete annotations as hypothetical proteins. Our recent elucidation of AETX biosynthesis established functions of the two previously unknown proteins as enzymes responsible for tryptophan halogenation (AetF) and nitrile synthesis (AetD). Given their sequence novelty, we queried metagenomic data sets for these two enzymes and identified two new cyanobacterial haloindole biosynthetic gene clusters (BGCs) from marine sediment in Moorea, French Polynesia, and soil-derived samples in Maunawili Falls, Hawaii. We characterized the recovered BGCs by biochemically validating a new AetF homologue that exclusively halogenates free indole, rather than tryptophan as observed in AETX biosynthesis, and a new AetD homologue that harbors distinct substrate preferences, expanding the scope of nitrile biosynthesis. Additional characterization of core and accessory enzymes within these AETX-like BGCs highlights the breadth and diversity of haloindole biosynthetic machinery in cyanobacteria.

Sorghum bicolor, an important global crop, adapted to thrive in hotter and drier conditions than maize or rice, has deep roots that interact with a stratified soil microbiome that plays a crucial role in plant health, growth, and carbon storage. Microbiome studies on agricultural soils, particularly fields growing S. bicolor, have been mostly limited to surface soils (<30 cm). Here we investigated the abiotic factors of soil properties, field location, depth, and the biotic factors of sorghum type across 38 genotypes of the soil microbiome. Utilizing 16S rRNA gene amplicon sequencing, our analysis reveals significant changes in microbial composition and decreasing diversity at increasing soil depths within S. bicolor fields, regardless of genotype or field, with microbial richness and diversity declining to a minimum at the 60-90 cm layer and increasing beyond the 90 cm depth. Notably, specific microbial families, such as Thermogemmatisporaceae and an unclassified family within the ABS-6 order, were enriched in deeper soil layers beyond 30 cm. These findings highlight the importance of soil depth in agricultural soil microbiome studies.IMPORTANCESorghum bicolor is a valuable model for studying the microbiome in deep soils, which is crucial for enhancing carbon sequestration in agricultural systems. As we look to crops with deeper roots for improved carbon storage, it is essential to move beyond the traditional focus on surface soils in agricultural settings. This study shifts that focus by investigating microbial dynamics at greater soil depths, revealing significant changes in microbial composition and diversity with increasing depth, revealing the critical role of deep-soil microbiomes in nutrient cycling and carbon sequestration in agricultural fields with the deep-rooted crop S. bicolor. By exploring these processes beyond surface soils, this research supports the development of sustainable agricultural practices that can better harness the potential of deep-rooted crops for long-term carbon storage.

Microbiome research is revolutionizing human and environmental health, but the value and reuse of microbiome data are significantly hampered by the limited development and adoption of data standards. While several ongoing efforts are aimed at improving microbiome data management, significant gaps still remain in terms of defining and promoting adoption of consensus standards for these datasets. The Strengthening the Organization and Reporting of Microbiome Studies (STORMS) guidelines for human microbiome research have been endorsed and successfully utilized by many research organizations, publishers, and funding agencies, and have been recognized as a consensus community standard. No equivalent effort has occurred for environmental, synthetic, and non-human host-associated microbiomes. To address this growing need within the microbiome research community, we convened the Microbiome Data Management in Action Workshop (June 12–13, 2024, in Atlanta, GA, USA), to bring together key decision makers in microbiome science including researchers, publishers, funders, and data repositories. The 50 attendees, representing the diverse and interdisciplinary nature of microbiome research, discussed recent progress and challenges, and brainstormed actionable recommendations and paths forward for coordinated environmental microbiome data management and the modifications necessary for the STORMS guidelines to be applied to environmental, non-human host, and synthetic microbiomes. The outcomes of this workshop will form the basis of a formalized data management roadmap to be implemented across the field. These best practices will drive scientific innovation now and in years to come as these data continue to be used not only in targeted reanalyses but in large-scale models and machine learning efforts.