Title

The diversity and evolution of phenazine biosynthesis pathways in Enterobacterales

Date of Award

5-2021

Degree Type

Honors College Thesis

Academic Program

Biological Sciences BS

Department

Biological Sciences

First Advisor

Dmitri Mavrodi, Ph.D.

Advisor Department

Biological Sciences

Abstract

Enterobacterales is an order of Gram-negative bacteria that encompasses plant and animal pathogens and organisms of industrial importance. Some of these bacteria produce secondary metabolites classified as phenazines (Phz). Studies in other groups of microorganisms revealed that phenazines are redox-active and exhibit broad antibacterial, antifungal, and antiparasitic activity. Enterobacterales are known to produce phenazines, but details about the diversity, biochemistry, and function of phenazine metabolites in these organisms are missing. In this work, we screened the National Center for Biotechnology Information (NCBI) GenBank for genome sequences of phenazine-producing (Phz+) Enterobacterales. Additionally, genomes of Phz+ strains Pectobacterium carotovorum cc303 and P. betavasculorum Ecb168 were sequenced, assembled, annotated, and used in downstream analyses. Scaffolds containing phz clusters were extracted and analyzed for the presence of the core biosynthesis, phenazine modifying, and resistance genes. These deoxyribonucleic acid (DNA) sequences were analyzed for the presence of site-specific recombinases and transposases. The evolution of phz pathways was analyzed by comparing phylogenies of the core phenazine biosynthesis and housekeeping genes. The results of this study revealed an unexpected and widespread presence of phenazine genes in Enterobacterales. We identified at least six distinct types of phenazine clusters in Escherichia coli, Shigella, Klebsiella, Enterobacter, Pantoeae, Brenneria, Serratia, Xenorhabdus, Photorhabdus, and Providencia. In many strains, phz genes formed parts of genomic islands or were associated with plasmids, suggesting their spread via horizontal gene transfer and contribution to the competition for the ecological niche between closely related taxa.

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