# Host and nonhost bacteria support bacteriophage dissemination along mycelia and abiotic dispersal networks

## TL;DR

This study shows how bacteriophages spread through soil using fungal networks and bacterial carriers, even without moving on their own.

## Contribution

The study demonstrates that both host and nonhost bacteria can help bacteriophages spread through fungal highways in soil.

## Key findings

- Bacteriophages spread more effectively on fungal highways with over 20 connecting hyphae.
- Host bacteria are five times more effective at transporting bacteriophages than nonhost bacteria.
- Abiotic networks alone limit bacteriophage diffusion, but fungal highways enhance it significantly.

## Abstract

Bacteriophages play a crucial role in shaping bacterial communities, yet the mechanisms by which nonmotile bacteriophages interact with their hosts remain poorly understood. This knowledge gap is especially pronounced in structured environments like soil, where spatial constraints and air-filled zones hinder aqueous diffusion. In soil, hyphae of filamentous microorganisms form a network of ‘fungal highways’ (FHs) that facilitate the dispersal of other microorganisms. We propose that FHs also promote bacteriophage dissemination. Viral particles can diffuse in liquid films surrounding hyphae or be transported by infectable (host) or uninfectable (nonhost) bacterial carriers coexisting on FH networks. To test this, two bacteriophages that infect Pseudomonas putida DSM291 (host) but not KT2440 (nonhost) were used. In the absence of carriers, bacteriophages showed limited diffusion on 3D-printed abiotic networks, but diffusion was significantly improved in Pythium ultimum-formed FHs when the number of connecting hyphae exceeded 20. Transport by both host and nonhost carriers enhanced bacteriophage dissemination. Host carriers were five times more effective in transporting bacteriophages, particularly in FHs with over 30 connecting hyphae. This study enhances our understanding of bacteriophage dissemination in nonsaturated environments like soils, highlighting the importance of biotic networks and bacterial hosts in facilitating this process.

Demonstration of the important positive role of host carriers and fungal highways in the dissemination of bacteriophages in soil.