Molecular ecological characterisation of high-latitude bacterioplankton

• Main Author: Priest, Taylor
• Other Authors: Eren, A. Murat, Fuchs, Bernhard, Acinas, Silvia González
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2022
• Subjects: marine bacteria; Arctic Ocean; metagenomics; metagenome-assembled genomes; microbial communities; long-read metagenomics; microbial ecology; 500; 500 Science; ddc:500; Arctic; Fram Strait; Sea ice
• Online Access: https://media.suub.uni-bremen.de/handle/elib/6672; https://doi.org/10.26092/elib/2032; https://nbn-resolving.org/urn:nbn:de:gbv:46-elib66729

The Arctic Ocean is undergoing irreversible perturbations as a result of accelerated climate warming. Of major significance is the expanding influence of Atlantic water that expedites sea-ice decline, alters stratification and vertical mixing of the water column and facilitates northward expansion of temperate biota. Our understanding on how these processes will impact biological communities is severely limited. The Fram Strait is the primary entry route for Atlantic water into the Arctic Ocean and exit point for polar water and sea-ice. With the presence of two major current systems combined with horizontal mixing processes, the Fram Strait is characterised by a longitudinal gradient of hydrographic regimes reflective of Arctic, mixed and Atlantic conditions. This provides an invaluable opportunity to study the ecology of microbes over an environmental gradient and under changing conditions. Furthermore, given its high-latitude position, it also facilitates investigations on how dramatic seasonal transformations in conditions, such as sea-ice cover and light availability, influence microbes in the context of water mass history. This thesis provides an ecological characterisation of microbial communities over temporal and spatial scales in the Fram Strait in an effort to address these topics. In Chapter II, we employed metagenomics from short- and long-read sequencing platforms to gain insights into microbial community composition across water masses in the Fram Strait. As that study incorporated the first PacBio HiFi (long-read) metagenomes from the marine environment, it was necessary to perform a methodological comparison. We show that using PacBio HiFi metagenomes, we are able to recover more metagenome-assembled genomes (MAGs) that, on average, are more complete, less fragmented and more frequently contain complete rRNA gene operons compared to using short-read metagenomes. This not only influenced our investigative toolkit throughout the remainder of this thesis but provides valuable data for future ...