Undergraduate Honors Thesis Projects

Date of Award

Spring 2026

Document Type

Honors Paper

Degree Name

Biochemistry and Molecular Biology-BS

Department

Biology & Earth Science

Advisor

Dr. Jennifer Bennett

First Committee Member

Dr. John Tansey

Second Committee Member

Louise Captein MFA

Keywords

Streptomyces, Development, Cyclic Di-GMP, Signaling

Subject Categories

Biochemistry | Biology | Higher Education | Molecular Biology

Abstract

Cyclic di-GMP is a ubiquitous bacterial second messenger that governs critical developmental transitions in Streptomyces coelicolor, including transitions from vegetative growth to aerial hyphae formation and sporulation. This study integrates computational, metabolic, and transcriptomic approaches to elucidate the regulatory architecture of the c-di-GMP signaling pathway, with a focus on the diguanylate cyclase CdgC and the phosphodiesterases RmdA and RmdB. Using Struc2Net-based structural homology modeling, we predict a high-confidence signaling hub centered on CdgA, RmdA, and RmdB with protein pairs having interaction scores higher than 0.8 respectively. CdgC also demonstrated strong predicted interactions with these regulators, having scores between 0.71 and 0.75 along with a moderate self-interaction propensity of 0.548. These predictions are being experimentally validated using the bacterial adenylate cyclase two-hybrid system to assess CdgC homodimerization and heterocomplex formation in vivo. Parallel phenotypic characterization of RmdA and RmdB mutants via Biolog Microbial Phenotype Assays revealed metabolic reprogramming consistent with elevated intracellular c-di-GMP levels. Both mutants exhibited hyper-metabolism of complex carbohydrates, increased utilization of purines, and altered nitrogen metabolism, reflecting a sustained vegetative state driven by c-di-GMP-stabilized BldD-mediated repression of sporulation. Osmolyte sensitivity profiles diverged between the two mutants, suggesting non-overlapping stress adaptation functions. Complementary RNA-seq analysis will profile genome-wide transcriptional changes in these mutants to identify differentially expressed genes and downstream pathways influenced by RmdA and RmdB activity. These findings provide mechanistic insight into the molecular regulation of development in these industrially important antibiotic-producing bacteria, with the potential implications for optimizing secondary metabolite production.

Licensing Permission

Copyright, all rights reserved. Fair Use

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