Affiliation:
1. BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, Michigan, USA
2. Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
Abstract
ABSTRACT
In 2016, Michigan experienced the largest outbreak of shigellosis, a type of bacillary dysentery caused by
Shigella
spp., since 1988. Following this outbreak, we isolated 16 novel
Shigella
-infecting bacteriophages (viruses that infect bacteria) from environmental water sources. Most well-known bacteriophages infect the common laboratory species
Escherichia coli
and
Salmonella enterica
, and these phages have built the foundation of molecular and bacteriophage biology. Until now, comparatively few bacteriophages were known to infect
Shigella
spp., which are close relatives of
E. coli
. We present a comprehensive analysis of these phages' host ranges, genomes, and structures, revealing genome sizes and capsid properties that are shared by very few previously described phages. After sequencing, a majority of the
Shigella
phages were found to have genomes of an uncommon size, shared by only 2% of all reported phage genomes. To investigate the structural implications of this unusual genome size, we used cryo-electron microscopy to resolve their capsid structures. We determined that these bacteriophage capsids have similarly uncommon geometry. Only two other viruses with this capsid structure have been described. Since most well-known bacteriophages infect
Escherichia
or
Salmonella
, our understanding of bacteriophages has been limited to a subset of well-described systems. Continuing to isolate phages using nontraditional strains of bacteria can fill gaps that currently exist in bacteriophage biology. In addition, the prevalence of
Shigella
phages during a shigellosis outbreak may suggest a potential impact of human health epidemics on local microbial communities.
IMPORTANCE
Shigella
spp. bacteria are causative agents of dysentery and affect more than 164 million people worldwide every year. Despite the need to combat antibiotic-resistant
Shigella
strains, relatively few
Shigella
-infecting bacteriophages have been described. By specifically looking for
Shigella
-infecting phages, this work has identified new isolates that (i) may be useful to combat
Shigella
infections and (ii) fill gaps in our knowledge of bacteriophage biology. The rare qualities of these new isolates emphasize the importance of isolating phages on “nontraditional” laboratory strains of bacteria to more fully understand both the basic biology and diversity of bacteriophages.
Funder
MoSTR | National Science Foundation
American Association for the Advancement of Science
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
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