Still, oceanographers did not recognize their central role in N 2 fixation until the 1960s (e.g. Fitting with this long-term recognition, scientists defined six morphologically described species in the late 1800s. Trichodesmium filaments can aggregate in natural communities, forming 1–4 mm colonies of essentially two morphologies (i.e., radial tufts or spherical puffs ) that are visible to the naked eye and thus aided these early observations. as ‘sea-saw dust’ for hundreds of years because of the massive surface blooms they can form resembling small, water-suspended wood shavings. Mariners have known filamentous Trichodesmium spp. ), the filamentous, colony-forming cyanobacterium Trichodesmium is still considered a critical oceanic nitrogen fixer. While our understanding of nitrogen-fixing organisms in the oceans is evolving to include non-autotrophic diazotrophs and other unexpected physiologies (e.g. In the warm, oligotrophic open ocean, these low nitrogen concentrations select for nitrogen-fixing organisms that can efficiently convert atmospheric N 2 to bioavailable forms. Low bioavailable concentrations of nitrogen can limit primary productivity in many oceanic euphotic zones (e.g.
erythraeum does not, identifies Trichodesmium as an ecologically important CRISPR-Cas model system, and highlights the need for more research on phage- Trichodesmium interactions. thiebautii maintaining CRISPR-Cas systems, while T. thiebautii, could put this outcome in question. erythraeum is expected to be a ‘winner’ of anthropogenic climate change, their genomic dearth of known phage resistance mechanisms, compared to T. Additionally, the system was expressed in metaproteomic and transcriptomic datasets and CRISPR spacer sequences with 100% identical hits to field-assembled, putative phage genome fragments were identified. thiebautii, and correlated with increased signatures of horizontal gene transfer. erythraeum genomes, vertically inherited by T. Surprisingly, this CRISPR-Cas system was absent in all T. thiebautii MAGs are enriched in COG defense mechanisms and encode a vertically inherited Type III-B Clustered Regularly Interspaced Short Palindromic Repeats and associated protein-based immunity system (CRISPR-Cas).
thiebautii dominating the colony-specific reads. Phylogenomics identified ~four N 2 fixing clades of Trichodesmium across the transect, with T.
To address these questions, we describe Trichodesmium pangenomic potential via significantly improved genomic assemblies from two isolates and 15 new >50% complete Trichodesmium metagenome-assembled genomes from hand-picked, Trichodesmium colonies spanning the Atlantic Ocean. Despite this central biogeochemical role, many questions about their evolution, physiology, and trophic interactions remain unanswered. are considered one of the most important nitrogen-fixing genera in the warm, low nutrient ocean. The colony-forming cyanobacteria Trichodesmium spp.
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