Project description:Organic substrate transfer between photoautotrophic and heterotrophic microbes in the surface ocean is a central but poorly understood process in the global carbon cycle. This study developed a co-culture system of marine diatom Thalassiosira pseudonana and heterotrophic bacterium Ruegeria pomeroyi, and addressed diel changes in phytoplankton endometabolite production using nuclear magnetic resonance (NMR) and bacterial metabolite consumption using gene expression. Here we deposit data for NMR analysis from the study. Samples were collected every 6 hours over two days under a diel light cycle. During the course of the study, we observed an increase in some phytoplankton endometabolites presumably due to the effects of the associated bacteria. We introduced an additional experiment and tested this possibility by comparing phytoplankton endometabolite accumulation between axenic treatments and bacteria coculture treatments.
Project description:Phytoplankton-derived metabolites fuel a large fraction of heterotrophic bacterial production in the global ocean, yet methodological challenges have limited our knowledge of organic molecules transferred between these two microbial groups. In an experimental bloom study in which the diatom Thalassiosira pseudonana was co-cultured with three heterotrophic marine bacteria, we concurrently measured diatom endometabolites (i.e., potential exometabolite supply) by nuclear magnetic resonance (NMR) spectroscopy and bacterial gene expression (i.e., potential exometabolite uptake) by metatranscriptomic sequencing.
Project description:We isolate the cultivable microbiome of a diatom and show that different bacteria have commensal, antagonistic, or synergistic effects on the diatom. One synergistic bacterium enhances growth of the diatom by production of auxin, a phytohormone. The diatom and its synergistic bacterium appear to use auxin and tryptophan as signaling molecules that drive nutrient exchange. Detection of auxin molecules and biosynthesis gene transcripts in the Pacific Ocean suggests that these interactions are widespread in marine ecosystems.
Project description:Alternative splicing (AS) generates isoform diversity critical for cellular identity and homeostasis, yet characterization of this diversity in single cells remains limited. We developed Expedition, a computational framework to categorize and visualize the heterogeneity of AS from single-cell transcriptomes. Expedition consists of (i) outrigger, a de novo splice graph transversal algorithm to detect AS from single cell RNA-seq; (ii) anchor, a Bayesian approach to assign splicing modalities and (iii) bonvoyage, using non-negative matrix factorization to visualize modality changes. By applying Expedition to single iPSCs undergoing neuron differentiation, we discover that 25% of AS exons exhibit bimodality and are flanked by longer and more conserved introns harboring distinct cis-regulatory motifs. Bimodal exons are highly dynamic during cellular transitions, preserve translatability, enriched in recently emerged genes and have conserved AS in mammals. Applying Expedition (http://github.com/YeoLab/Expedition) in single cells redefines our estimates and understanding of AS in evolution and biology.
