ABSTRACT

Planktonic marine bacteria significantly impact global elemental cycling, productivity, and water quality. Recent evidence shows that abundant and diverse marine bacterioplankton require external vitamin B1 or precursors (B1 herein) to survive, and addition of these nutrients stimulates bacterial production. This suggests that it is favorable for most marine bacteria to rely on supplied B1, making B1 dynamics an environmentally relevant test case to study nutrient exchanges within the planktonic microbiome. Notably though, links between extracellular B1 availability and the composition, function, and fitness of marine bacteria are poorly understood. This project sheds light on 1) which activities and interactions are modulated by B1 availability, and 2) the benefits of exogenous B1 use by ubiquitous marine bacterioplankton. Experiments are being conducted to address uncertainty regarding B1 limitation of natural bacterioplankton, help predict plankton responses to natural or anthropogenic increases in B1 and reveal more on the rules governing nutrient exchange between plankton. Greater knowledge of the advantages of bacterial B1 use will benefit fields beyond oceanography, such as synthetic biology which focuses on streamlined microbial product generation. B1-deficiency in animals is a current concern in marine ecosystems. Greater knowledge of costs and quotas at the microbial level will position the larger community to ask deficiency questions at other trophic levels. The teaching and training components of this project include support for graduate students and a post-doctoral scholar. The major outreach component is a newly conceived Mobile Aquatic Microbial Laboratory (MAML) that seeks to improve public awareness of aquatic microbes and their ecosystem impact, as well as convey concepts of nutrient limitation and why cells need vitamins. Pre- and post-assessment and social distancing measures are integrated into MAML, as are incentives for participants to share images via social media and contribute to the program.

This project investigates the impact of vitamin B1 and B1 congeners on bacterioplankton in marine ecosystems where vitamin limitation is poorly understood. The work is conducted in the Neuse River estuary, the second largest estuary in the lower USA, and in the offshore coastal ocean. Nutrient amendment experiments are being conducted to test whether B1/congeners modulate bacterioplankton growth, composition, and gene transcription (reflecting putative function). Complementary lab-based experiments with wildtype and genetically engineered bacterioplankton are being conducted to test whether use of exogenous B1/congener significantly improves cell fitness and to address why reliance upon exogenous B1/congener is so prevalent among wild bacterioplankton. Additional lab experiments with isolates are being conducted to examine the protein-related cost of B1 de novo biosynthesis versus exogenous B1/congener use as well as cell quotas of B1 and precursors using mass spectrometry techniques. The work reaches beyond recent genome-based extrapolations to address how exogenous B1/congener availability shapes bacterioplankton metabolism, community structure, microbial interactions, and fitness.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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