Elizabeth Mann

I am a microbial ecologist with a broad interest in using interdisciplinary approaches to determine how microbes respond to multiple environmental stresses. More specifically, my research focuses on how marine microbial populations respond to either limiting or toxic concentrations of metals and how these responses are shaped by other environmental factors such as nutrient and light availability as well as the presence of other species. The scope of my projects has ranged from quantifying basic ecological information such as how fast a species is growing in the field to determining how relationships among intracellular regulatory pathways influence gene expression. All of my projects are multidisciplinary and would not be possible without collaborations with chemists, bioinformatics specialists and modelers.

An active area of marine research is the limitation of ecosystem productivity by iron. Nearly all organisms on Earth require iron to thrive, but the supply of this metal falls short of demand in vast areas of the oceans, including the Southern Ocean, Equatorial Pacific and subarctic Pacific. As a result, the growth rates and productivity of even the smallest marine algae – the cyanobacteria, are significantly limited by iron. Iron limitation of marine heterotrophic bacteria also has substantial biogeochemical implications since iron limitation reduces the efficiency with which microbes incorporate carbon dioxide into cellular material. Marine bacteria also impact iron in seawater through the production of siderophores – compounds specifically produced by microbes to harvest iron by forming strong bonds with this metal. Understanding how bacteria respond to low iron concentrations is important outside of marine science as well, since the ability to acquire sufficient iron to support rapid growth is one prerequisite for establishing an infection.

One current project focuses on how iron limitation affects carbon utilization and siderophore production in marine bacteria. Possible links between iron regulatory networks and carbon utilization were investigated by defining the genes controlled by the iron responsive, small regulatory RNA RyhB. RyhB facilitates the degradation of mRNA coding for non-essential iron containing enzymes when iron is in short supply and also acts to increase the availability of siderophore precursors. The RyhB regulon in the marine bacterium Vibrio fischeri was defined by directly comparing gene expression patterns in normal cells with those of mutants lacking RyhB using global transcriptome analyses (RNA-Seq) and qRT-PCR assays. Based on these results, iron limitation may affect the regulation of genes governing amino acid and carbohydrate metabolism as well as transport.

Other research projects follow the same general theme, investigating how microorganisms respond to metals in the environment using field research and molecular methods. These studies have focused on how iron and light co-limitation could structure phytoplankton populations in suboxic water columns and on the differences in the ability of microbes to tolerate copper and arsenate.

To learn more, visit https://www.researchgate.net/profile/Elizabeth_Mann5

Contact Elizabeth at elizabeth <dot> mann at ronininstitute /dot/ org