Formation of phage lysis patterns and implications on co-propagation of phages and motile host bacteria.

Xiaochu Li,Birgit E Scharf,Jing Chen,Nathaniel Esteves,Floricel Gonzalez,Benjamin Althouse

doi:10.1371/journal.pcbi.1007236

Abstract

Coexistence of bacteriophages, or phages, and their host bacteria plays an important role in maintaining the microbial communities. In natural environments with limited nutrients, motile bacteria can actively migrate towards locations of richer resources. Although phages are not motile themselves, they can infect motile bacterial hosts and spread in space via the hosts. Therefore, in a migrating microbial community coexistence of bacteria and phages implies their co-propagation in space. Here, we combine an experimental approach and mathematical modeling to explore how phages and their motile host bacteria coexist and co-propagate. When lytic phages encountered motile host bacteria in our experimental set up, a sector-shaped lysis zone formed. Our mathematical model indicates that local nutrient depletion and the resulting inhibition of proliferation and motility of bacteria and phages are the key to formation of the observed lysis pattern. The model further reveals the straight radial boundaries in the lysis pattern as a telltale sign for coexistence and co-propagation of bacteria and phages. Emergence of such a pattern, albeit insensitive to extrinsic factors, requires a balance between intrinsic biological properties of phages and bacteria, which likely results from coevolution of phages and bacteria.

Highlights

Viruses that target bacteria, bacteriophages or phages, are critical components of the microbial world
In a migrating microbial community, coexistence between phages and host bacteria implies that they co-propagate in space
We report a novel phage lysis pattern that is indicative of this co-propagation

Summary

Introduction

Viruses that target bacteria, bacteriophages or phages, are critical components of the microbial world They are found in almost every natural environment, including soil, waters, oceans, and bodies of macroorganisms (e.g., human guts) [1,2,3]. They are the most abundant organisms in the biosphere [2]. Through their interactions with bacteria, phages constantly regulate the ecology, evolution, and physiology of microbial communities [1, 2] Because of their antimicrobial activity, the application of phages in food processing, agriculture, and medicine has exploded in recent years [4,5,6]. Development of these applications benefits from fundamental knowledge about how phages interact with bacteria in a microbial community and how they are dispersed in their microenvironment

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