Independent host- and bacterium-based determinants protect a model symbiosis from phage predation

• Published in: Cell reports (Cambridge) 2022-02, Vol.38 (7), p.110376-110376, Article 110376
• Main Authors: Lynch, Jonathan B., Bennett, Brittany D., Merrill, Bryan D., Ruby, Edward G., Hryckowian, Andrew J.
• Format: Article
• Language: English
• Subjects: Aliivibrio fischeri - virology; Animals; bacterial genetics; bacteriophages; Bacteriophages - genetics; Bacteriophages - isolation & purification; Bacteriophages - physiology; Bacteriophages - ultrastructure; Decapodiformes - microbiology; Extracellular Polymeric Substance Matrix - metabolism; genomic analysis; Host-Pathogen Interactions - physiology; microbe-host interactions; model systems; Models, Biological; Mutation - genetics; Plankton - metabolism; symbiosis; Symbiosis - physiology
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2022.110376

Bacteriophages (phages) are diverse and abundant constituents of microbial communities worldwide, capable of modulating bacterial populations in diverse ways. Here, we describe the phage HNL01, which infects the marine bacterium Vibrio fischeri. We use culture-based approaches to demonstrate that mutations in the exopolysaccharide locus of V. fischeri render this bacterium resistant to infection by HNL01, highlighting the extracellular matrix as a key determinant of HNL01 infection. Additionally, using the natural symbiosis between V. fischeri and the squid Euprymna scolopes, we show that, during colonization, V. fischeri is protected from phages present in the ambient seawater. Taken together, these findings shed light on independent yet synergistic host- and bacterium-based strategies for resisting symbiosis-disrupting phage predation, and we present important implications for understanding these strategies in the context of diverse host-associated microbial ecosystems. [Display omitted] •A Vibrio fischeri-infecting bacteriophage, HNL01, is isolated and characterized•HNL01 does not disrupt the mutualism between V. fischeri and Euprymna scolopes•HNL01-resistant V. fischeri mutants rapidly emerge in vitro•When HNL01 is present, squid colonization by HNL01-resistant V. fischeri is favored Lynch et al. isolate and characterize a bacteriophage that infects the marine bacterium Vibrio fischeri. They show that the mutualism between V. fischeri and the Hawaiian bobtail squid Euprymna scolopes is not disrupted by phages present in the environment and highlight both bacterium- and squid-based determinants of protecting this mutualism against phage predation.