Genomic Insights into the Marine Microbial Response to Oil Spills: Biogeographic Priming, Cryptic Hydrocarbon Cycling, and Substrate Specialization

• Main Author: Arrington, Eleanor C
• Other Authors: Valentine, David L
• Format: Thesis
• Language: English
• Published: eScholarship, University of California 2021
• Subjects: Microbiology; Ecology; Aquatic sciences; Genomics; Metaproteomics; Oil; Petroleum; Phylogenetics; North Atlantic
• Online Access: https://escholarship.org/uc/item/7ws3n1v5; https://escholarship.org/content/qt7ws3n1v5/qt7ws3n1v5.pdf

Our seas, oceans, and coastal zones are under great stress and pollution, particularly by crude oil, which fuels the global economy. Subsurface petroleum reservoirs originate from geo-thermo-chemical reactions on biological debris over millions of years, resulting in a complex heterogeneous mixture of hydrocarbons, with major components consisting of alkanes with different chain lengths and branch points, cycloalkanes, branched cycloalkanes, mono-aromatic, and polycyclic aromatic hydrocarbons. Populations of hydrocarbon-degrading bacteria, including many species that cannot utilize other carbon sources, are present in all marine systems and play an important role in turnover and fate of these compounds. In this dissertation, the microbial response to petroleum components is probed in multiple environments to understand the role different chemical fractions play in eliciting different niches of oil consumers, and to identify factors controlling basal seed populations of hydrocarbon degraders poised to bloom to petroleum disasters. Through study in the subtropical North Atlantic Ocean, a cryptic long-chain alkane cycle has been confirmed, originating from cyanobacteria, dwarfing the quantity of other petroleum inputs to the ocean. In Chapter 1, I demonstrate waters in the mesopelagic underlying the photic zone hosted n-alkane degrading bacteria that bloomed rapidly when fed pentadecane, exhibiting exponential oxygen loss due to respiration within a week. Parallel experiments performed with sinking particles collected in situ from beneath the deep chlorophyll maximum—representing an export flux of particulate-phase pentadecane and its microbial consumers from the euphotic zone—exhibited similarly rapid bloom timing with pentadecane, but with greater oxygen decline. Notably, bloom onset timing for other petroleum compounds with no biogenic origin in the mesopelagic is an order of magnitude slower compared to biogenic alkanes. Metagenomic analyses of pentadecane blooms exposes the metabolic pathways used for ...