Maria Hadjifrangiskou, Ph.D., is a professor at Vanderbilt University Medical Center and serves as Senior Assistant Dean for Biomedical Research Education and Training. She came to the United States in 1996 on a Fulbright Scholarship to pursue undergraduate studies in molecular biology. Falling in love with bacterial physiology, she continued her education at the University of Texas-Houston.

Under the tutelage of Theresa Koehler, Ph.D., Hadjifrangiskou delineated transcriptional mechanisms that control the expression of the anthrax toxin genes. During her doctoral work, she developed a passion for bacterial gene regulation, cell signaling and community behavior.

Hadjifrangiskou joined the Hultgren group as a post-doctoral researcher, where she elucidated determinants that influence biofilm formation and bacterial “decision-making.”

Hadjifrangiskou is fascinated with how bacterial pathogens change their transcriptional programs in response to unique micro-environments they encounter in the host. The urinary tract poses a unique niche for such studies: Bacteria encounter pressure changes, nutritional fluxes, oxygen concentration oscillations and other microbes depending on where they are “geographically” found in the urinary tract. Understanding these molecular “tag-and-pulls” is critical for homing in on pathogen programs that facilitate pathogen persistence. Since joining Vanderbilt, Hadjifrangiskou has established a vibrant research group and educational environment that addresses these questions.

Seasonality of Archaea from North Carolina’s Coastal Estuaries and into the Gulf Stream

Though once thought to be the ‘Domain of Life’ containing extremophiles exclusively, Archaea are now known to inhabit nearly every biome on Earth. Of these ‘nonextremophilic’ Archaea, Thaumarchaeota are among the most abundant organisms on the planet and play a key role in the nitrogen cycle, oxidizing ammonia to nitrite as the first step in nitrification. Although typically viewed as a single entity, subgroups within Thaumarchaeota (Phylum Thermoproteota, Class Nitrososphaeria) have predictable abundance patterns based on environment (e.g., depth, salinity, pH), and thus have been termed ‘ecotypes’. Distinct ecotypes are found in freshwater, marine, soil, and hot spring environments; in North Carolina, Thaumarchaeota are both abundant and active in aquatic environments spanning the coast-to-offshore continuum. My laboratory’s research focuses on how Thaumarchaeota diversity, abundance, and activity are affected by environmental factors using a combination of molecular biology and geochemical techniques. Through this interdisciplinary approach, we have found that these archaea ‘bloom’ seasonally in the Cape Fear River Estuary, actively transform nitrogen within invertebrate hosts along the NC coast (including sea squirts and oysters), and inhabit distinct water masses in the Atlantic Ocean from Wilmington into the Gulf Stream. These datasets complement laboratory-based cultivation of Thaumarchaeota and experiments mimicking environmental change. Taken together, this combination of field and laboratory studies across a variety of aquatic ecosystems improve our understanding of this important archaeal group and their impact.