Phage Morons Play an Important Role in Pseudomonas aeruginosa Phenotypes

Abstract

The viruses that infect bacteria, known as phages, play a critical role in controlling bacterial populations in many diverse environments, including the human body. This control stems not only from phages killing bacteria but also from the formation of lysogens. In this state, the phage replication cycle is suppressed, and the phage genome is maintained in the bacterial cell in a form known as a prophage. Prophages often carry genes that benefit the host bacterial cell, since increasing the survival of the host cell by extension also increases the fitness of the prophage. These highly diverse and beneficial phage genes, which are not required for the life cycle of the phage itself, have been referred to as "morons," as their presence adds "more on" the phage genome in which they are found. While individual phage morons have been shown to contribute to bacterial virulence by a number of different mechanisms, there have been no systematic investigations of their activities. Using a library of phages that infect two different clinical isolates of , PAO1 and PA14, we compared the phenotypes imparted by the expression of individual phage morons. We identified morons that inhibit twitching and swimming motilities and observed an inhibition of the production of virulence factors such as rhamnolipids and elastase. This study demonstrates the scope of phage-mediated phenotypic changes and provides a framework for future studies of phage morons. Environmental and clinical isolates of the bacterium frequently contain viruses known as prophages. These prophages can alter the virulence of their bacterial hosts through the expression of nonessential genes known as "morons." In this study, we identified morons in a group of phages and characterized the effects of their expression on bacterial behaviors. We found that many morons confer selective advantages for the bacterial host, some of which correlate with increased bacterial virulence. This work highlights the symbiotic relationship between bacteria and prophages and illustrates how phage morons can help bacteria adapt to different selective pressures and contribute to human diseases.

Two Lineages of Pseudomonas aeruginosa Filamentous Phages: Structural Uniformity over Integration Preferences

“…In general, prophages’ accessory or additional genes are those dispensable for their life cycles, hence, acronymized as “morons”—derived simply from “more on” meaning or called “lysogenic conversion genes” ( Brüssow et al. 2004 ; Tsao et al. 2018 ).…”

Pf Bacteriophage and Their Impact on Pseudomonas Virulence, Mammalian Immunity, and Chronic Infections

“…Accessory genes flank the core Pf genome (Figure 2) and are known as morons (they add more genes on) (81). While the functions of Pf phage morons are not well-characterized, other phage morons have been shown to reduce virulence factor production and inhibit Pa motility (82). Due to the presence of these accessory genes, the overall size of the Pf genome is variable amongst different Pf strains, ranging from ∼7-12 kb.…”

Transcriptomic determinants of the response of ST-111 Pseudomonas aeruginosa AG1 to ciprofloxacin identified by a top-down systems biology approach

“…Although general information on PaeAG1 phages is scarce, there is evidence to suggest that JBD44 is one of the most prevalent in P. aeruginosa 95 . Effects of JBD44 induction on growth have been previously described in P. aeruginosa PAO1, showing that JBD44 expression significantly decreased the growth of PAO1, unlike other phages 96 . Similarly, SOS-mediated phage induction has been reported in P. aeruginosa PAO1 12 , 26 and LESB58 97 .…”