NETWORK ANALYSIS REVEALS CONSERVED PROTEIN CLUSTERS AND RHIZOSPHERE-DRIVEN BIOGEOGRAPHY IN BRADYRHIZOBIUM PHAGES
Date
2025-05
Authors
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Publisher
University of Delaware
Abstract
Bradyrhizobia are nitrogen-fixing bacteria that form symbiotic nodules on the
roots of leguminous plants, supplying their hosts with fixed nitrogen in exchange for
photosynthetic products. This symbiosis reduces the need for chemical fertilizers,
which in excess can lead to eutrophication and toxic algal blooms, ultimately
contribute to climate change. Consequently, the Bradyrhizobium-legume relationship
is recognized for its economic, ecological, and agricultural significance. However,
bacteriophages can shape this mutualistic relationship by regulating host bacterial
populations. The impact of bacteriophages on soil nutrient cycles and food web
interactions remains poorly understood, therefore contributing to the need for further
investigation into soil viral populations and their ecological roles.
In this study, we used previously isolated and sequenced Bradyrhizobium
phage (bradyphage) population representative genomes from Delaware soybean field
soil samples as references. Through metagenomic analysis, we identified uncultivated
viral genomes (UViGs) in environmental samples that share significant protein
homology with these bradyphages. Our results reveal conserved functional gene
groups, especially those involved in phage infection and replication, indicating the
essential roles of structural and DNA synthesis proteins. We also found bradyphages
to exhibit strong genomic similarity to UViGs from soil and rhizosphere
environments, suggesting adaptation to similar ecological niches. By identifying
conserved gene clusters and characterizing genome features of bradyphages, this work
provides a foundation for future research on viral-host interactions, with implications
for engineering phages to enhance nitrogen fixation in sustainable agriculture. Our
findings expand the known diversity of soil viruses and highlight the importance of
phage research in understanding and managing soil microbial communities.