Comparative analysis reveals host-dependent diversity in 16 novel Bradyrhizobium bacteriophages
Date
2024
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Bacteriophages, or phages for short, are a group of viruses that infect bacteria. They are the most abundant biological entity on the planet, outnumbering their bacterial hosts 10-fold in some ecosystems. Phages shape ecosystems by controlling host abundance, driving host evolution via horizontal gene transfer and aiding in the cycling of nutrients. Bradyrhizobium is an important genus of bacteria, due to the ability of some species to nodulate the roots of soybean (Glycine max), where it supplies its host with a direct source of biologically fixed nitrogen. Optimizing this symbiosis can reduce or eliminate the use of polluting synthetic nitrogen fertilizers, making agriculture more sustainable and environmentally friendly. The presence of phages in soil ecosystems likely impacts the symbiotic relationship between soybean and its Bradyrhizobium partners by altering competition between strains of Bradyrhizobium for root nodulation sites. Studying these phages could eventually help farmers harness their abilities to control nodulation competition to promote nodulation and nitrogen fixation by more symbiotically effective strains and thereby sustainably enhance soybean yields. ☐ My research characterized sixteen virulent phages isolated from ten Delaware soils that infect Bradyrhizobium strains symbiotic with soybean. These phages were examined for their host range and morphology, and by full genome DNA sequencing and analysis. These analyses revealed host-specific diversity in phage morphotypes and genomic composition and identified four distinct and novel phage species. All phages isolated against B. elkanii, regardless of the bacterial strain against which they were isolated, had very similar morphologies and host ranges and were grouped together into one species based on their nucleotide identity. The phages isolated against B. diazoefficiens were more diverse and, based on nucleotide identity, represented three unique species of phage. The B. elkanii phages studied could be of future interest due to their broad host ranges and ability to lyse less symbiotically efficient Bradyrhizobium strains, therefore making these phages potential candidates for enhancing soybean yield by controlling nodulation in favor of highly effective N-fixers.
Description
Keywords
Bacteriophages, Genomics, Lytic cycle, Virulent phages, Viruses