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Abstract Aqueous-soluble hydrocarbons dissolve into the ocean’s interior and structure deep-sea microbial populations influenced by natural oil seeps and spills. Among these hydrocarbons, n-pentane, is a seawater-soluble, volatile compound abundant in petroleum products and reservoirs, which partially partitions to the deep-water column following release from the seafloor. In this study, we explore the ecology and niche partitioning of two free-living Cycloclasticus strains recovered from seawater incubations with n-pentane and distinguish them as an open ocean variant and a seep-proximal variant, each with distinct capabilities for hydrocarbon catabolism. Comparative metagenomic analysis indicates the variant more frequently observed further from natural seeps encodes more general pathways for hydrocarbon consumption, including short-chain alkanes, aromatics, and long-chain alkanes, and also possesses redox versatility in the form of respiratory nitrate reduction and thiosulfate oxidation; in contrast, the seep variant specializes in short-chain alkanes and relies strictly on oxygen as the terminal electron acceptor. Both variants observed in our work were dominant ecotypes of Cycloclasticus observed during the Deepwater Horizon disaster, a conclusion supported by 16S rRNA gene analysis and read-recruitment of sequences collected from the submerged oil plume during active flow. A comparative genomic analysis of Cycloclasticus across various ecosystems suggests distinct strategies for hydrocarbon transformations among each clade. Our findings suggest Cycloclasticus is a versatile and opportunistic consumer of hydrocarbons and may have a greater role in the cycling of sulfur and nitrogen, thus contributing broad ecological impact to various ecosystems globally. 

ABSTRACT Teleost fishes are a highly diverse, ecologically essential group of aquatic vertebrates that include coho salmon (Oncorhynchus kisutch). Coho are semelparous and all ovarian follicles develop synchronously. Owing to their ubiquitous distribution, teleosts provide critical sources of food worldwide through subsistence, commercial fisheries, and aquaculture. Enhancement of hatchery practices requires detailed knowledge of teleost reproductive physiology. Despite decades of research on teleost reproductive processes, an in‐depth proteome of teleost ovarian development has yet to be generated. We have described a coho salmon ovarian proteome of over 5700 proteins, generated with data independent acquisition, revealing the proteins that change through the transition from primary to secondary ovarian follicle development. This transition is critical during the onset of puberty and for determining egg quality and embryonic development. Primary follicle development was marked by differential abundances of proteins in carbohydrate metabolism, protein turnover, and the complement pathway, suggesting elevated metabolism as the follicles develop through stages of oogenesis. The greatest proteomic shift occurred during the transition from primary to secondary follicle growth, with increased abundance of proteins underlying cortical alveoli formation, extracellular matrix reorganization, iron binding, and cell–cell signaling. This work provides a foundation for identifying biomarkers of salmon oocyte stage and quality. 

Abstract Diatoms are important primary producers in the world's oceans, yet their growth is constrained in large regions by low bioavailable iron (Fe). Low‐Fe stress‐induced limitation of primary production is due to requirements for Fe in components of essential metabolic pathways including photosynthesis and other chloroplast plastid functions. Studies have shown that under low‐Fe stress, diatoms alter plastid‐specific processes, including components of electron transport. These physiological changes suggest changes of protein content and in protein abundances within the diatom plastid. While in silico predictions provide putative information on plastid‐localized proteins, knowledge of diatom plastid proteins remains limited in comparison to well‐studied model photosynthetic organisms. To address this, we employed shotgun proteomics to investigate the proteome of subcellular plastid‐enriched fractions fromThalassiosira pseudonanato gain a better understanding of how the plastid proteome is remodeled in response to Fe limitation. Using mass spectrometry‐based peptide identification and quantification, we analyzedT. pseudonanagrown under Fe‐replete and ‐limiting conditions. Through these analyses, we inferred the relative quantities of each protein, revealing that Fe limitation regulates major metabolic pathways in the plastid, including the Calvin cycle. Additionally, we observed changes in the expression of light‐harvesting proteins. In silico localization predictions of proteins identified in this plastid‐enriched proteome allowed for an in‐depth comparison of theoretical versus observed plastid‐localization, providing evidence for the potential of additional protein import pathways into the diatom plastid.