Research Seminar – Jess Boulton

The UNC-CH Department of Marine Sciences presents a research seminar from graduate student, Jess Boulton. This event will be held on Monday, November 23rd, at 12:00 pm. However, this seminar is remote only and can be viewed online via Zoom (Meeting ID: 974 6573 2747).

Seminar Title: Transcriptional markers of organic substrate availability in a coastal marine bacterium

Abstract: Bacterial metabolism strongly influences the cycling of dissolved organic carbon (DOC) through the ocean. Marine cycling of organic matter is essential for ocean ecosystem function, and affects ocean carbon sequestration. Our understanding of the processes and mechanisms involved in organic matter cycling in the ocean (as well as how these processes may change) is limited by a lack of information about the composition of the DOC pool. This pool of carbon is difficult to measure chemically, due to the high diversity of carbon compounds, low concentrations of individual compounds, and high temporal and spatial variability. One proposed method towards understanding more about the dissolved organic carbon pool is to use environmental metatranscriptomics to identify which carbon compounds a bacterial community is consuming in situ. However, there is a lack of experimentally validated information about which transcripts correlate to the presence of carbon substrates. In this study, we sought to increase the utility of metatranscriptomics data by quantitatively linking gene expression to availability of defined carbon substrates. Cells of a model organism, Ruegeria pomeroyi DSS3, were grown in 18 carbon-limited continuous cultures to test their response to 4 carbon sources: glucose, benzoate, glycerol, and acetate. We found complex patterns of gene upregulation in response to all four substrates. Glucose treatments showed no significant differences in gene expression between high and low glucose concentrations. Genes upregulated in glucose treatments included galM, a glucokinase, an alcohol dehydrogenase, and a putative xyl operon. 3 genes were enriched in all Benzoate treatments: 2 were Aromatic benzoate oxidation (Box) genes, the third was a hypothetical protein. An 11- gene operon centered around the Box genes was enriched in high-concentration benzoate treatments only. Few genes for glycerol degradation pathways were enriched in glycerol treatments of any concentration. Instead, upregulation of HK97 phage genes and amino acid synthesis/degradation pathway genes were observed. Growth on acetate did not significantly alter transcription of upper-level degradation pathway genes.