| Summary: | Fragilariopsis cylindrus is an ecologically significant diatom inhabiting sea ice and water column assemblages in the Southern Ocean (SO). Microbial growth in SO microbial communities has been demonstrated to be periodically limited or co-limited by vitamin B12. In this dissertation, I examine the molecular consequences of B12 deprivation in F. cylindrus, with a focus on alterations to protein expression and metabolite production. Despite unchanged growth rates, B12-deprived F. cylindrus cells display responses that can impact the production of growth stimulating compounds, including induction of a putative B12 remodeling pathway and differential production of DMSP and thiamine related compounds. My findings highlight that assessments of marine phytoplankton’s responses to stressors beyond growth rate should be considered in order to generate accurate predictions of community interactions in micronutrient deprived environments. These results have implications for our understanding the relationship between B12 availability and community composition and nutrient cycling in a changing ocean.
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