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bioRxiv · 10.1101/2024.08.08.607087

Hydrocarbon Metabolism and Petroleum Seepage as Ecological and Evolutionary Drivers for Cycloclasticus

Arrington, E. C.·Tarn, J.·Kivenson, V.·Nunn, B. L.·Liu, R. M.·Paul, B. G.·Valentine, D. L.
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Abstract

Aqueous-soluble hydrocarbons dissolve into the oceans interior and structure deep-sea microbial populations influenced by natural oil seeps and spills. n-Pentane is a seawater-soluble, volatile compound abundant in petroleum products and reservoirs and will partially partition 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 using 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 open ocean adapted variant 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 analysis and read-recruitment of sequences 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.

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Arrington, E. C., Tarn, J., Kivenson, V., Nunn, B. L., Liu, R. M., Paul, B. G., Valentine, D. L.. 2024-08-09. Hydrocarbon Metabolism and Petroleum Seepage as Ecological and Evolutionary Drivers for Cycloclasticus. https://doi.org/10.1101/2024.08.08.607087

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