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Free S higa toxin 1‐encoding bacteriophages are less prevalent than S higa toxin 2 phages in extraintestinal environments
Author(s) -
GrauLeal Ferran,
Quirós Pablo,
MartínezCastillo Alexandre,
Muniesa Maite
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13053
Subject(s) - lytic cycle , biology , infectivity , microbiology and biotechnology , bacteriophage , extracellular , escherichia coli , bacteria , gene , virology , genetics , virus
Summary S tx bacteriophages are involved in the pathogenicity of S tx‐producing E scherichia coli . Induction of the S tx phage lytic cycle increases S tx expression and releases S tx phages that reach extracellular environments. S tx phage family comprises different phages that harbour any stx subtype. S tx2 is closely related with severe disease and therefore previous studies focused on free S tx2 phages in extraintestinal environments. To provide similar information regarding S tx1 phages, we evaluate free S tx1 phages in 357 samples of human and animal wastewater, faeces, river water, soil, sludge and food. Our method, based on quantification of stx 1 in the DNA from the viral fraction, was validated using electron microscopy counting of phages and infectivity. The overall prevalence of S tx1 phages was very low: 7.6% of positive samples and values below 3 × 10 3 GC (gene copies) ml −1 . These results contrast starkly with the abundance of S tx2 phages in the samples (68.4%). This environmental scarcity of free S tx1 phages is attributed to their lower rates of induction and the fact that S tx1 does not require phage induction to be expressed because it possesses an independent promoter. The implications of the low prevalence of free S tx1 phages for the emergence of new pathogenic strains in the environment are discussed.