生物
原噬菌体
志贺毒素
遗传学
GenBank公司
溶酶原
基因组
多位点序列分型
基因
毒力
噬菌体
大肠杆菌
基因型
作者
Stefanía B. Pascal,Ramiro Lorenzo,María Victoria Nieto Farias,John W. A. Rossen,Paula María Alejandra Lucchesi,Alejandra Krüger
出处
期刊:AIMS microbiology
[American Institute of Mathematical Sciences]
日期:2023-01-01
卷期号:9 (3): 570-590
标识
DOI:10.3934/microbiol.2023030
摘要
<abstract> <p>Shiga toxin-producing <italic>E. coli</italic> (STEC) are diarrheagenic strains that can cause bloody diarrhea and hemolytic-uremic syndrome. Their main virulence factor, the Shiga toxin (Stx), is encoded by phages integrated into the bacterial chromosome. Stx phages are widely diverse and carry many genes with limited or unknown function. As the toxin subtype Stx2a is associated with highly pathogenic strains, this study was mainly focused on the characterization of the <italic>stx</italic> flanking region of Stx2a phages. Of particular interest was a sialate O-acetylesterase (NanS-p), which has been described previously to be encoded downstream <italic>stx</italic> in some phage genomes and may confer a growth advantage for STEC. Complete DNA sequences of Stx2a phages and prophages were retrieved from the GenBank database, and the genomic regions from anti-terminator Q to holin S genes were bioinformatically analyzed. Predicted NanSp sequences from phages encoding other Stx subtypes were also studied. Additionally, expression of <italic>nan</italic>S-p was quantified by qPCR in strains selected from our laboratory collection. The analysis of Stx2a phage genomes showed that all carried the <italic>Q</italic>, <italic>stx</italic><sub>2a</sub>, <italic>nan</italic>S-p and <italic>S</italic> genes, but with allele diversity and other sequence differences. In particular, sequence differences were detected in each of the three domains of NanS-p esterases encoded by Stx2a phages and other Stx phages; however, <italic>nan</italic>S-p was not identified in the Stx2e, Stx2f and Stx2g phages analyzed. The expression of <italic>nan</italic>S-p increased in most <italic>stx</italic><sub>2a</sub>-positive strains under phage inducing conditions, as was previously shown for <italic>stx</italic><sub>2a</sub>. As the present work showed diversity at the Q-S region among Stx phages, and particularly in the encoded NanS-p enzyme, future studies will be necessary to evaluate if NanS-p variants differ in their activity and to assess the impact of the absence of <italic>nan</italic>S-p in certain Stx phages.</p> </abstract>
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