Open AccessThe large‐sized plasmids of enterohemorrhagic Escherichia coli O157 strains encode hemolysins which are presumably members of the E. coli α‐hemolysin family
Author(s) -
Schmidt Herbert,
Karch Helge,
Beutin Lothar
Publication year - 1994
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1994.tb06763.x
Subject(s) - hemolysin , plasmid , escherichia coli , microbiology and biotechnology , biology , genetics , virulence , dna , gene
Most enterohemorrhagic Escherichia coli O157:H7 strains harbor a large‐sized (90 kb) plasmid designated pO157 and show an enterohemolytic phenotype. In this study the hemolytic activity of E. coli O157:H7 strain EDL933 was investigated. Curing of strain EDL933 from pO157 resulted in loss of its hemolytic activity. By transformation with Tn801‐tagged pO157 (pSK3), the hemolysin‐negative E. coli K‐12 strains C600 and DH5 became positive for hemolysin production. By transformation of recombinant plasmids carrying a 11.9 kb Bam HI fragment and a 5.3 kb Sal I fragment of pSK3 hemolytic activity is revealed when tranformed in E. coli C600 or DH5α DNA‐hybridization of pO157 and subclones with the α‐hemolysin specific DNA probe was only found under conditions of low stringency. No hybridization was found with enterohemolysin I (EHly1) and enterohemolysin II (EHly2) probes. Our results indicate that a hitherto not described hemolysin belonging to the α‐hemolysin family is encoded by the 90 kb plasmid of E. coli O157 strains.