Excellence in Research: From genomics to ecophysiology: the adaptive metabolic strategy of heterotrophic marine Cyclobacterium species

The majority of microbial biodiversity in the ocean lies within the realm of the rare biosphere. These rare microbes are essential for ecosystem dynamics and play a central role in the carbon cycle from assimilation, storage, transformation, export, and remineralization of the largest pool of organic carbon on the planet. The members of bacteroidetes, are emerging as key players in the degradation of high molecular weight dissolved organic carbon (DOM).

In this research project, Cyclobacterium marinum Atlantic-IS, a member of bacteroidetes and part of the rare biosphere, will be studied to determine how C. marinum Atlantic-IS adjusts its growth in response to different DOM present in the marine environment. This project will examine how C. marinum Atlantic-IS adjust its growth in response to different DOM present in the marine environment and thus will enhance the understanding of microbial degradation of complex carbohydrates and the molecular processes involved in the usage of different organic carbons.

This research has implications for understanding functional ecological significance of rare bacterial taxa in ocean ecosystems. This study actively engages undergraduate students of color. Students will gain knowledge and skillsets spanning molecular biology methods, microbial physiology, and quantitative data analysis.

This training will contribute to student retention in STEM, increase diversity, and workforce development. This project will strengthen research capabilities of the principal investigator and build research capacity at a historically Black College and University (HBCU). A partnership between the HBCU and Woods Hole Oceanographic Institution will be established.

The annotated draft genome of C. marinum Atlantic-IS, which was collected from benthic water of the Atlantic Ocean, contains higher than expected number of polysaccharide utilization genes, hydrolases, and transport-related proteins that would allow the bacterium to survive under famine conditions and bloom when DOM is abundant. In addition, it contains a large number of regulatory genes, which could be pivotal for the generation of swift and adaptable metabolic responses to changing DOM in the environment.

The principal investigator will test the hypothesis that C. marinum with its large number of polysaccharide utilization genes, transporters, and regulatory genes is able to adapt to changing carbon sources in oligotrophic oceans. This hypothesis will be tested by combining transcriptomics, proteomics, and physiological approaches to understand the expression of various transporters and regulatory networks that trigger the use of select polysaccharides and polymeric glycans thought to be abundant in the ocean.

In particular, the expression of numerous transporter systems in response to different carbon sources and the speed of response to changing carbon sources will be determined. Ultimately, this research will enhance the understanding of heterotrophic bacteria in the ocean and their ecophysiology.

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.