Catechin, a novel root exudate of Centaurea stoebe, exhibits pleiotropic effects on the soil microbial community and individual soil isolates, and undergoes chemical changes with numerous abiotic factors from soil
Allelopathy has been studied for (±)-catechin, a root exudate of spotted knapweed, as a plausible mechanism that facilitates knapweed invasion in North America. Phytotoxic effects are observed in invaded fields as well as greenhouse experiments when employing catechin or growing spotted knapweed, demonstrating similar effects on native plant species. However, many studies ignore the impact of catechin on microbial populations in soil. Understanding the impact of catechin on microbial processes will greatly aid our understanding of how spotted knapweed invasion can alter soil chemistry and biological processes. Chapter 2 will address the impact of soil and media parameters on catechin stability and extraction from soil. My results show catechin to be a highly reactive compound and that redox metals, the pH of the surrounding environment, and the aerobicity of the system can greatly alter catechin auto-oxidation rates. Chapter 3 expands on these findings by testing the impact of catechin-metal complexes on catechin phytotoxicity reported in the current literature. I demonstrate metals that lower the amount "pure" catechin in the system have differential effects on native plant species. I further reveal that conditions of increased environmental stress can further exacerbate this phytotoxic phenomenon. Chapter 4 addresses the impact of catechin on soil bacterial communities as well as individual bacterial populations. I confirm that catechin is not bacteriocidal, but instead should be categorized as bacteriostatic. In chapter 5, I extend the findings in chapter 4 to include a repressive effect to various bacterial genera but show that species capable of altering catechin stability can overcome this bacteriostatic effect. More importantly, I reveal that two simple organic acids were capable of restoring previously inhibited bacterial species. Chapter 6 focuses on the ability of catechin to prevent endospore formation, germination, and to alter cell morphology in many gram-positive endospore-forming bacteria commonly found in soil. The significance of this body of work is outlined in chapter 7 along with directions that future research might take to explore some of my more obscure findings.
bacteriostatic, catechin, filament, microbial, polyphenol, sporostatic
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