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Extracellular Enzymes in Aquatic Environments University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 8-2020 Extracellular Enzymes in Aquatic Environments: Possible Role of Non-Specific eptidasesP in Microcystin Degradation and Effects of Assay Protocol on Calculated Activities Christopher Cook University of Tennessee Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Recommended Citation Cook, Christopher, "Extracellular Enzymes in Aquatic Environments: Possible Role of Non-Specific Peptidases in Microcystin Degradation and Effects of Assay Protocol on Calculated Activities. " Master's Thesis, University of Tennessee, 2020. https://trace.tennessee.edu/utk_gradthes/6073 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Christopher Cook entitled "Extracellular Enzymes in Aquatic Environments: Possible Role of Non-Specific eptidasesP in Microcystin Degradation and Effects of Assay Protocol on Calculated Activities." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Geology. Andrew Steen, Major Professor We have read this thesis and recommend its acceptance: Annette Engel, Steven Wilhelm Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) EXTRACELLULAR ENZYMES IN AQUATIC ENVIRONMENTS: POSSIBLE ROLE OF NON-SPECIFIC PEPTIDASES IN MICROCYSTIN DEGRADATION AND EFFECTS OF ASSAY PROTOCOL ON CALCULATED ACTIVITIES A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Christopher Lee Cook August 2020 Copyright © 2020 by Christopher Lee Cook All rights reserved. ii DEDICATION I dedicate this work to my dog and friend of sixteen years. Farewell, Godzilla. iii ACKNOWLEDGEMENTS I would first like to thank my advisor, Drew Steen. He is an extremely helpful mentor who is truly invested in each of his graduate students. I could not have asked for a better advisor. I would also like to thank my committee members, Steve Wilhelm and Annette Engel. I am grateful to the Wilhelm research group, especially Lauren Krausfeldt, for training me to perform microbiology laboratory work. This research was funded in part by the Office of Research Interdisciplinary Research Seed Program – Novel pathways for microcystin degradation in aquatic environments. I would like to thank my fellow graduate students. They helped share the load during stressful times. I would especially like to thank the Royalty family. Taylor, Brittany, and Dylan Royalty have been great resources and friends since my arrival as a graduate student. Taylor, another member of the Steen research group, taught me how to endure the academic lifestyle. Finally, I would like to thank my family for all of their support throughout my two years in graduate school. iv ABSTRACT Extracellular enzyme assays are widely used methods to probe the interactions between microbes and complex organic matter. Microbes produce extracellular enzymes to degrade macromolecules into smaller molecules that can be transported across cell membranes. Enzyme assays provide a quantitative understanding of the rates and specificities of extracellular enzymes toward these macromolecules. This study explored 1) the biodegradation pathways of microcystin-LR (MC-LR), a cyanobacterial peptide toxin, by measuring the activities of extracellular peptidases produced by putative MC- LR degraders and 2) the effects of enzyme assay protocol on activity measurements, which involved the creation of ezmmek, an R package designed to analyze enzyme assay data reproducibly under different protocols. Lactobacillus rhamnosus GG, an MC-LR degrader that employs an unknown pathway, produces L-Leucine aminopeptidases. Future work can test whether these same peptidases are capable of degrading MC-LR. Two enzyme assay protocols were applied to the same freshwater sample, but resulted in significantly different activity measurements when analyzed with ezmmek. Widespread adoption of ezmmek could standardize enzyme analytical pathways performed by other researchers, and will make results more comparable among MC-LR and other organic matter degradation studies. v TABLE OF CONTENTS INTRODUCTION ......................................................................................... 1 Microcystin-LR ............................................................................................................... 1 Impacts on Human and Ecosystem Health ................................................................. 1 Production and Degradation Mechanisms .................................................................. 2 Biodegradation by Non-Specific Pathways ................................................................ 2 Extracellular Enzyme Assays ......................................................................................... 3 Michaelis-Menten Kinetics ......................................................................................... 3 Application to Ecosystem Studies .............................................................................. 4 References ....................................................................................................................... 6 Appendix ....................................................................................................................... 10 PEPTIDASES PRODUCED BY PUTATIVE MICROCYSTIN-LR DEGRADERS................................................................................................................... 15 Abstract ......................................................................................................................... 16 Introduction ................................................................................................................... 16 Extracellular Peptidases in Freshwater Systems ....................................................... 16 Evidence for Non-Specific Degradation ................................................................... 17 Testing for Non-specific Degradation ...................................................................... 18 Methods......................................................................................................................... 18 Incubation Parameters ............................................................................................... 18 Enzyme Assays ......................................................................................................... 19 Results and Discussion ................................................................................................. 20 Enzyme Assay Data Analysis ................................................................................... 20 Combining Enzyme Assays with MC-LR Degradation Experiments ...................... 20 Conclusions ................................................................................................................... 21 References ..................................................................................................................... 23 Appendix ....................................................................................................................... 26 ezmmek: AN R PACKAGE TO ANALYZE EXTRACELLULAR ENZYME ACTIVITIES ON SYNTHETIC SUBSTRATES ........................................... 34 Abstract ......................................................................................................................... 35 Introduction ................................................................................................................... 35 Optimization of Extracellular Enzyme Assays ......................................................... 35 Protocol Descriptions ................................................................................................ 36 Methods......................................................................................................................... 39 Design of ezmmek .................................................................................................... 39 Sample and Site Description ..................................................................................... 40 Enzyme Assay Procedure ......................................................................................... 41 Results and Discussion ................................................................................................. 43 ezmmek Performance................................................................................................ 43 Enzyme Assay Method Analysis .............................................................................. 43 Conclusions ................................................................................................................... 46 References ..................................................................................................................... 48 Appendix ....................................................................................................................... 51 CONCLUSION
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