Virus Infection of Aspergillus fumigatus Compromises the Fungus in Intermicrobial Competition.

Hasan Nazik,Ioly Kotta-Loizou,Gabriele Sass,David A Stevens,Robert H A Coutts

doi:10.3390/v13040686

Abstract

Aspergillus and Pseudomonas compete in nature, and are the commonest bacterial and fungal pathogens in some clinical settings, such as the cystic fibrosis lung. Virus infections of fungi occur naturally. Effects on fungal physiology need delineation. A common reference Aspergillus fumigatus strain, long studied in two (of many) laboratories, was found infected with the AfuPmV-1 virus. One isolate was cured of virus, producing a virus-free strain. Virus from the infected strain was purified and used to re-infect three subcultures of the virus-free fungus, producing six fungal strains, otherwise isogenic. They were studied in intermicrobial competition with Pseudomonas aeruginosa. Pseudomonas culture filtrates inhibited forming or preformed Aspergillus biofilm from infected strains to a greater extent, also seen when Pseudomonas volatiles were assayed on Aspergillus. Purified iron-chelating Pseudomonas molecules, known inhibitors of Aspergillus biofilm, reproduced these differences. Iron, a stimulus of Aspergillus, enhanced the virus-free fungus, compared to infected. All infected fungal strains behaved similarly in assays. We show an important consequence of virus infection, a weakening in intermicrobial competition. Viral infection may affect the outcome of bacterial–fungal competition in nature and patients. We suggest that this occurs via alteration in fungal stress responses, the mechanism best delineated here is a result of virus-induced altered Aspergillus iron metabolism.

Highlights

Viruses naturally infecting Aspergillus wild-type strains have been known since1970 [1]
Effect of virus infection on A. fumigatus physiology in the context of the assays to be performed: To assist in interpretation of possible P. aeruginosa effects on A. fumigatus in the assays selected to test such effects, we needed to assess A. fumigatus function in the absence of P. aeruginosa, which is the A. fumigatus control we would use for assessing P. aeruginosa effects
Seven experiments assessing A. fumigatus biofilm metabolism were performed in the milieu to be used for later testing P. aeruginosa effects: RPMI 1640, in the plates, temperature, etc., described

Summary

Introduction

Viruses naturally infecting Aspergillus wild-type strains have been known since. These viruses have double-stranded (ds) or single-stranded (ss) RNA genomes and may be conventionally encapsidated. They do not have an extracellular phase in their replication cycle but can be transmitted horizontally via hyphal fusion and vertically via spore production. Little is known about how they affect Aspergillus physiology or virulence. The virus family Polymycoviridae was initially reported in 2015 [2] and was officially recognized by the International Committee on Taxonomy of Viruses in 2020 Polymycoviridae currently accommodate one genus Polymycovirus and 10 species, including Aspergillus fumigatus polymycovirus

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