Summary
A bioRxiv preprint maps bacterial host factors involved in infection by single-stranded RNA and DNA bacteriophages. The study identifies conserved requirements for F-pilus-dependent infection and links an E. coli capsule architecture to selective phage access.
A genome-wide study has mapped bacterial genes and cellular systems involved in infection by single-stranded RNA and single-stranded DNA bacteriophages. The bioRxiv preprint, posted on September 18, 2026, reports genetic screens in Escherichia coli that identify shared and group-specific host requirements, including factors involved in viral entry and the condition of the bacterial cell envelope.
The work focuses on phages that use the F pilus, a filament-like structure on the bacterial surface, to reach the cell. The authors describe the resulting map as a framework for studying poorly characterised phage-host interactions and for guiding future diagnostic, protein-antibiotic and biocontrol technologies.
Shared entry machinery, with an important exception
Bacteriophages are viruses that infect bacteria. In this study, the researchers examined single-stranded RNA phages spanning all four genogroups of the class Leviviricetes, alongside filamentous single-stranded DNA phages. Genetic screens track how changes in bacterial genes affect the success of infection, allowing researchers to identify host factors that a phage requires or that interfere with its life cycle.
Across the RNA phages, the screens found a highly conserved network of host dependencies. Structural components of the F pilus were required across the tested lineages, as was DsbA-mediated disulfide-bond formation, a process that helps maintain the pilus's structure. These findings point to a shared requirement for an intact F pilus even among phage groups with other biological differences.
The F-plasmid gene traD was a notable exception. Although the phages use the same primary receptor, traD was essential for entry in some genogroups but not others. This group-specific dependence indicates that interaction with a common receptor can still lead to different requirements during the next stages of infection.
The gene-dosage screens also identified potential barriers to infection. Increasing the copy number of hslU, which encodes a protease component, or stpA, an RNA chaperone, restricted infection in the tested systems. The result shows that the amount of a host factor can influence phage infection, not just whether the corresponding gene is present.
For the filamentous single-stranded DNA phages, the assays produced host-factor profiles consistent with earlier work while revealing additional variations in dependency. The phages required the host TolQRA complex for entry after engagement with the pilus. TolQRA is a membrane-associated system that can transfer energy across the bacterial envelope; in this infection pathway, the study places it downstream of pilus contact.
An E. coli host that filters which phages can enter
The study also examined why its isolation host, E. coli HSF, is selective for particular phages. The researchers traced this selectivity to a capsule architecture acquired horizontally from Klebsiella. A bacterial capsule is a surface layer that can act as a physical barrier to virus attachment.
In the reported experiments, this capsule excluded a large panel of double-stranded DNA phages isolated on different E. coli strains. At the same time, single-stranded RNA and DNA phages could engage the extended F pilus and bypass the barrier through native pilus retraction. The finding links the surface architecture of the host to the kinds of phages that can be recovered using it.
The assays also showed prominent negative fitness signatures in groups of genes involved in cellular homeostasis. The authors associate these signatures with the physiological burden of continuous, non-lytic virion extrusion, in which filamentous phages leave the cell without immediately rupturing it and place stress on the bacterial envelope.
The immediate result is a comparative genetic map of phage infection in an E. coli system. The authors propose that such maps could help expand access to uncultured viral diversity and provide design principles for tools intended to detect, inhibit or control bacterial processes such as horizontal gene transfer. Those applications are future uses of the study's findings rather than technologies demonstrated in the preprint.
The evidence is a bioRxiv preprint based on bacterial genetic screens and phage-host experiments. Its conclusions therefore describe the tested E. coli systems; how broadly the identified dependencies transfer to other bacterial species remains a research question.