Biochemicals produced by organisms perform a diverse array of functions in the surrounding environment. Concentrations are decreased through biodegradation, the action of extracellular enzymes, and chemical reactions with dissolved and particulate-bound geochemicals.
Hypotheses: (1) Iron and manganese (hydr)oxides, prevalent in soils and sediments, are major sinks for excreted biochemicals. (2) Pathways and rates of these chemical reactions can be predicted based on knowledge of the identity, number, and arrangement of reactive functional groups within the biochemical structure.
Objective: develop an understanding of relationships between biochemical structure and chemical reactivity that can serve as the basis for predicting pathways and rates of reaction.
To illustrate our approach, consider the antibiotics penicillic acid, produced by fungi, and patulin, produced by mold. For these chemicals to persist long enough in soils to kill pathogenic or competitor bacteria, they must be resistant to oxidation by iron and manganese (hydr)oxides. In addition to studying the two biochemicals directly, we will also examine substructures Y1 and Y2 to learn more about how the arrangement of functional groups affect pathways and rates of oxidation by iron and manganese (hydr)oxides. Quorum-sensing (QS) signal compounds and QS inhibitor compounds are important aspects of this work. Oxidation and hydrolysis reactions involving Fe(OH)3(ferrihydrite) and FeOOH(goethite) will be emphasized.
Intellectual Merit: The proposed work serves as a bridge between geochemistry, physical organic chemistry, and microbiology/ecology. It facilitates a new activity: predicting pathways and rates of chemical transformation for newly-discovered biochemicals as a function of their structure/functional groups and prevalent geochemical conditions. Greater appreciation for the geochemical context for particular extracellular biochemicals, in turn, will encourage molecular biologists to seek novel natural products and regulatory mechanisms.
Broader Impacts: The nature of the proposed work entices students to cross traditional disciplinary boundaries, and engages them in new lines of inquiry. Undergraduates have changed their professional trajectories while in the PI's laboratory, e.g. from Chemical Engineering to Plant Science, from Chemistry to Environmental Engineering, from Geography to Environmental Chemistry. Nine of the PI's thirteen PhD graduates are women. One is now performing postdoctoral work in Molecular Biology. For this project, we seek recruits from underrepresented backgrounds that have these professional trajectories in mind.
One goal for the proposed work is to write tutorials at different levels, one for high school students and the general public, one for undergraduates, one for graduate students and researchers. In this way, individuals will have access to information that had not been available to them previously, and will be inspired to branch out and explore new fields.
