Molecular biomarkers of nitrogen status in diatoms and other microbes from Monterey Bay, CA

Gene expression in natural microbial communities is highly variable and is known to respond to factors including diel cycles, nutrient status, and microbial interactions. Because of this variability, there is great promise for using transcript and protein levels as bioindicators for microbial physiological states in situ. However, a major challenge in using molecular biomarkers (transcripts, proteins) to obtain insight into microbial cell states is that it is difficult to accurately interpret the highly dynamic signals. Accurate interpretation requires strong foundational knowledge to ground-truth putative genes, transcripts, or proteins that could serve as molecular physiological indicators. We used the most recent knowledge of how genes respond to variation in nitrogen source (nitrate, nitrite, ammonium) and overall nitrogen status (replete, deplete) in a model diatom, to infer the in situ physiological state of diatoms and other microbes from the Monterey Bay, in response to experimental nitrogen manipulations. The advantages and disadvantages of different putative molecular biomarkers for nitrogen status will be presented.