title: Haemolysin E- and enterohaemolysin-derived haemolytic activity of O55/O157 strains and other Escherichia coli lineages.
abstract: Among three haemolysins identified thus far in Escherichia coli, alpha-haemolysin (HlyA) is encoded on the pathogenicity islands of extraintestinal pathogenic strains, while enterohaemolysin (EhxA) is encoded on the virulence plasmids of enterohaemorrhagic E. coli (EHEC) strains. In contrast, the gene for haemolysin E (HlyE) is located on the E. coli chromosome backbone and is therefore widely distributed among E. coli strains. However, because hlyE gene expression is repressed by the H-NS protein and because the gene has been disrupted in many strains, its haemolytic activity cannot be detected in wild-type strains by routine screening on blood agar plates. In this study, we found that the HlyE-derived haemolytic activity of enteropathogenic E. coli (EPEC) O55 : H7 can be detected after anaerobic cultivation on a washed blood agar plate (EHX plate) that is used to detect the production of EhxA. We also found that the haemolytic activity of EHEC O157 : H7 observed on EHX plates under aerobic and anaerobic growth conditions is derived from EhxA and HlyE, respectively; this differential expression of the two haemolysins occurs at the transcriptional level. Our analysis of 60 E. coli strains of various pathotypes and phylogenies for their repertoires of haemolysin genes, haemolytic phenotypes and hlyE gene sequences revealed that HlyE activity can generally be detected on EHX plates under anaerobic growth conditions if the gene is intact. Furthermore, our results indicate that hlyE gene inactivation occurred in three of the five E. coli lineages (phylogroups A, B1 and B2), which demonstrates phylogroup-specific gene disruption patterns.
authors.affiliation: Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Murase
authors.affiliation: Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Tadasuke
authors.initials: T
authors.lastname: Ooka
authors.affiliation: Division of Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iguchi
authors.affiliation: Division of Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.|Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Yoshitoshi
authors.initials: Y
authors.lastname: Ogura
authors.affiliation: Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nakayama
authors.affiliation: Division of Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Md
authors.initials: M
authors.lastname: Asadulghani
authors.affiliation: Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Md Rakibul
authors.initials: MR
authors.lastname: Islam
authors.affiliation: Laboratory of Genomic Research on Pathogenic Bacteria, International Research Center for Infectious Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Hiyoshi
authors.affiliation: Department of Bacterial Infections, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kodama
authors.affiliation: National Reference Laboratory for Escherichia coli, Department of Biological Safety, Federal Institute for Risk Assessment (BfR), Diedersdorfer Weg 1, D-12277 Berlin, Germany.
authors.forename: Lothar
authors.initials: L
authors.lastname: Beutin
authors.affiliation: Division of Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.|Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hayashi
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism*; D006461:Hemolysis; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; C119944:hlyE protein, E coli