論文 - 井口 純
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Iguchi A., Iyoda S., Seto K., Ohnishi M.
Journal of Clinical Microbiology 49 ( 10 ) 3678 - 3680 2011年10月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Clinical Microbiology
This is the first report of the isolation of Shiga toxin-producing Escherichia coli (STEC) strains whose O antigens were genetically and serologically identical to those of Shigella boydii type 10, from human feces. The novel STEC O serogroup may be widespread in Japan and associated with diarrhea and hemorrhagic colitis. Copyright © 2011, American Society for Microbiology. All Rights Reserved.
DOI： 10.1128/JCM.01197-11
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Wide distribution of O157-antigen biosynthesis gene clusters in Escherichia coli
Iguchi A., Shirai H., Seto K., Ooka T., Ogura Y., Hayashi T., Osawa K., Osawa R.
PLoS ONE 6 ( 8 ) 2011年8月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：PLoS ONE
Most Escherichia coli O157-serogroup strains are classified as enterohemorrhagic E. coli (EHEC), which is known as an important food-borne pathogen for humans. They usually produce Shiga toxin (Stx) 1 and/or Stx2, and express H7-flagella antigen (or nonmotile). However, O157 strains that do not produce Stxs and express H antigens different from H7 are sometimes isolated from clinical and other sources. Multilocus sequence analysis revealed that these 21 O157:non-H7 strains tested in this study belong to multiple evolutionary lineages different from that of EHEC O157:H7 strains, suggesting a wide distribution of the gene set encoding the O157-a ntigen biosynthesis in multiple lineages. To gain insight into the gene organization and the sequence similarity of the O157-antigen biosynthesis gene clusters, we conducted genomic comparisons of the chromosomal regions (about 59 kb in each strain) covering the O-antigen gene cluster and its flanking regions between six O157:H7/non-H7 strains. Gene organization of the O157-antigen gene cluster was identical among O157:H7/non-H7 strains, but was divided into two distinct types at the nucleotide sequence level. Interestingly, distribution of the two types did not clearly follow the evolutionary lineages of the strains, suggesting that horizontal gene transfer of both types of O157-antigen gene clusters has occurred independently among E. coli strains. Additionally, detailed sequence comparison revealed that some positions of the repetitive extragenic palindromic (REP) sequences in the regions flanking the O-antigen gene clusters were coincident with possible recombination points. From these results, we conclude that the horizontal transfer of the O157-antigen gene clusters induced the emergence of multiple O157 lineages within E. coli and speculate that REP sequences may involve one of the driving forces for exchange and evolution of O-antigen loci. © 2011 Iguchi et al.
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Iguchi A., Umekawa N., Maegawa T., Tsuruta H., Odamaki T., Xiao J., Osawa R.
Antonie van Leeuwenhoek, International Journal of General and Molecular Microbiology 99 ( 3 ) 457 - 471 2011年3月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Antonie van Leeuwenhoek, International Journal of General and Molecular Microbiology
The polymorphism of ORFs encoding putative cell-surface adhesins was investigated in Bifidobacterium longum subsp. longum. Firstly, we performed a PCR assay targeting 15 ORFs encoding putative adhesion proteins, which included 8 ORFs with a sortase targeting LPXTG motif, in 42 strains of different pulsotypes isolated from fecal samples from 12 human individuals. We found a variability in the presence of an ORF, BL0675, which encodes a putative fimbrial subunit protein. We sequenced ORFs corresponding to BL0675 in the 42 strains and adjacent ORFs corresponding to BL0674 and BL0676. The results indicated that ORFs corresponding to BL0675 were highly polymorphic with five variant types (i.e. A-, B-, C-, D-, and E-types). Meanwhile, BL0674 and BL0676, which encode an additional putative fimbrial subunit protein and a fimbrial-associated sortase-like protein, were highly conserved. Subsequent quantitative polymerase chain reaction (qPCR) assays targeting the variant types in 89 human fecal samples revealed that A-type was the most commonly distributed (74.2%), followed by B-type (59.6%), D-type (31.5%), E-type (32.6%) and C-type (5.6% prevalence). Since BL0675 is considered to be a fimbrial protein with glycoprotein-binding ability, the proteins encoded by the five variant types of BL0675 may have specific binding properties to various carbohydrate structures expressed on the human intestinal wall, thereby allowing B. longum to colonize the intestine in a host-specific manner. © 2010 Springer Science+Business Media B.V.
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Nlec, a type III secretion protease, compromises NF-kB activation by targeting p65/rela
Yen H., Ooka T., Iguchi A., Hayashi T., Sugimoto N., Tobe T.
PLoS Pathogens 6 ( 12 ) 2010年12月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：PLoS Pathogens
The NF-kB signaling pathway is central to the innate and adaptive immune responses. Upon their detection of pathogen associated molecular patterns, Toll-like receptors on the cell surface initiate signal transduction and activate the NF-kB pathway, leading to the production of a wide array of inflammatory cytokines, in attempt to eradicate the invaders. As a countermeasure, pathogens have evolved ways to subvert and manipulate this system to their advantage. Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are closely related bacteria responsible for major food-borne diseases worldwide. Via a needle-like protein complex called the type three secretion system (T3SS), these pathogens deliver virulence factors directly to host cells and modify cellular functions, including by suppressing the inflammatory response. Using gain- and loss-of-function screenings, we identified two bacterial effectors, NleC and NleE, that down-regulate the NF-kB signal upon being injected into a host cell via the T3SS. A recent report showed that NleE inhibits NF-kB activation, although an NleE-deficient pathogen was still immune-suppressive, indicating that other antiinflammatory effectors are involved. In agreement, our present results showed that NleC was also required to inhibit inflammation. We found that NleC is a zinc protease that disrupts NF-kB activation by the direct cleavage of NF-kB's p65 subunit in the cytoplasm, thereby decreasing the available p65 and reducing the total nuclear entry of active p65. More importantly, we showed that a mutant EPEC/EHEC lacking both NleC and NleE (ΔnleC ΔnleE) caused greater inflammatory response than bacteria carrying ΔnleC or ΔnleE alone. This effect was similar to that of a T3SS-defective mutant. In conclusion, we found that NleC is an anti-inflammatory bacterial zinc protease, and that the cooperative function of NleE and NleC disrupts the NF-kB pathway and accounts for most of the immune suppression caused by EHEC/EPEC. © 2010 Yen et al.
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Ogura Y., Ooka T., Iguchi A., Toh H., Asadulghani M., Oshima K., Kodama T., Abe H., Nakayama K., Kurokawa K., Tobe T., Hattori M., Hayashi T.
Proceedings of the National Academy of Sciences of the United States of America 106 ( 42 ) 17939 - 17944 2009年10月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Proceedings of the National Academy of Sciences of the United States of America
Among the various pathogenic Escherichia coli strains, enterohemorrhagic E. coli (EHEC) is the most devastating. Although serotype O157:H7 strains are the most prevalent, strains of different serotypes also possess similar pathogenic potential. Here, we present the results of a genomic comparison between EHECs of serotype O157, O26, O111, and O103, as well as 21 other, fully sequenced E. coli/Shigella strains. All EHECs have much larger genomes (5.5-5.9 Mb) than the other strains and contain surprisingly large numbers of prophages and integrative elements (IEs). The gene contents of the 4 EHECs do not follow the phylogenetic relationships of the strains, and they share virulence genes for Shiga toxins and many other factors. We found many lambdoid phages, IEs, and virulence plasmids that carry the same or similar virulence genes but have distinct evolutionary histories, indicating that independent acquisition of these mobile genetic elements has driven the evolution of each EHEC. Particularly interesting is the evolution of the type III secretion system (T3SS). We found that the T3SS of EHECs is composed of genes that were introduced by 3 different types of genetic elements: an IE referred to as the locus of enterocyte effacement, which encodes a central part of the T3SS; SpLE3-like IEs; and lambdoid phages carrying numerous T3SS effector genes and other T3SS-related genes. Our data demonstrate how E. coli strains of different phylogenies can independently evolve into EHECs, providing unique insights into the mechanisms underlying the parallel evolution of complex virulence systems in bacteria.
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Ooka T., Terajima J., Kusumoto M., Iguchi A., Kurokawa K., Ogura Y., Asadulghani M., Nakayama K., Murase K., Ohnishi M., Iyoda S., Watanabe H., Hayashi T.
Journal of Clinical Microbiology 47 ( 9 ) 2888 - 2894 2009年9月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Clinical Microbiology
Enterohemorrhagic Escherichia coli O157 (EHEC O157) is a food-borne pathogen that has raised worldwide public health concern. The development of simple and rapid strain-typing methods is crucial for the rapid detection and surveillance of EHEC O157 outbreaks. In the present study, we developed a multiplex PCR-based strain-typing method for EHEC O157, which is based on the variability in genomic location of IS629 among EHEC O157 strains. This method is very simple, in that the procedures are completed within 2 h, the analysis can be performed without the need for special equipment or techniques (requiring only conventional PCR and agarose gel electrophoresis systems), the results can easily be transformed into digital data, and the genes for the major virulence markers of EHEC O157 (the stx1, stx2, and eae genes) can be detected simultaneously. Using this method, 201 EHEC O157 strains showing different XbaI digestion patterns in pulsed-field gel electrophoresis (PFGE) analysis were classified into 127 types, and outbreak-related strains showed identical or highly similar banding patterns. Although this method is less discriminatory than PFGE, it may be useful as a primary screening tool for EHEC O157 outbreaks. Copyright © 2009, American Society for Microbiology. All Rights Reserved.
DOI： 10.1128/JCM.00792-09
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Leopold S., Magrini V., Holt N., Shaikh N., Mardis E., Cagno J., Ogura Y., Iguchi A., Hayashi T., Mellmanng A., Karch H., Besser T., Sawyer S., Whittam T., Tarr P.
Proceedings of the National Academy of Sciences of the United States of America 106 ( 21 ) 8713 - 8718 2009年5月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Proceedings of the National Academy of Sciences of the United States of America
Single nucleotide polymorphisms (SNPs) in stable genome regions provide durable measurements of species evolution. We systematically identified each SNP in concatenations of all backbone ORFs in 7 newly or previously sequenced evolutionarily instructive pathogenic Escherichia coli O157:H7, O157:H -, and O55:H7. The 1,113 synonymous SNPs demonstrate emergence of the largest cluster of this pathogen only in the last millennium. Unexpectedly, shared SNPs within circumscribed clusters of organisms suggest severely restricted survival and limited effective population sizes of pathogenic O157:H7, tenuous survival of these organisms in nature, source-sink evolutionary dynamics, or, possibly, a limited number of mutations that confer selective advantage. A single large segment spanning the rfb-gnd gene cluster is the only backbone region convincingly acquired by recombination as O157 emerged from O55. This concatenomic analysis also supports using SNPs to differentiate closely related pathogens for infection control and forensic purposes. However, constrained radiations raise the possibility of making false associations between isolates.
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Asadulghani M., Ogura Y., Ooka T., Itoh T., Sawaguchi A., Iguchi A., Nakayama K., Hayashi T.
PLoS Pathogens 5 ( 5 ) 2009年5月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：PLoS Pathogens
Bacteriophages are major genetic factors promoting horizontal gene transfer (HGT) between bacteria. Their roles in dynamic bacterial genome evolution have been increasingly highlighted by the fact that many sequenced bacterial genomes contain multiple prophages carrying a wide range of genes. Enterohemorrhagic Escherichia coli O157 is the most striking case. A sequenced strain (O157 Sakai) possesses 18 prophages (Sp1-Sp18) that encode numerous genes related to O157 virulence, including those for two potent cytotoxins, Shiga toxins (Stx) 1 and 2. However, most of these prophages appeared to contain multiple genetic defects. To understand whether these defective prophages have the potential to act as mobile genetic elements to spread virulence determinants, we looked closely at the Sp1-Sp18 sequences, defined the genetic defects of each Sp, and then systematically analyzed all Sps for their biological activities. We show that many of the defective prophages, including the Stx1 phage, are inducible and released from O157 cells as particulate DNA. In fact, some prophages can even be transferred to other E. coli strains. We also show that new Stx1 phages are generated by recombination between the Stx1 and Stx2 phage genomes. The results indicate that these defective prophages are not simply genetic remnants generated in the course of O157 evolution, but rather genetic elements with a high potential for disseminating virulence-related genes and other genetic traits to other bacteria. We speculate that recombination and various other types of inter-prophage interactions in the O157 prophage pool potentiate such activities. Our data provide new insights into the potential activities of the defective prophages embedded in bacterial genomes and lead to the formulation of a novel concept of inter-prophage interactions in defective prophage communities. © 2009 Asadulghani et al.
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Iguchi A., Thomson N., Ogura Y., Saunders D., Ooka T., Henderson I., Harris D., Asadulghani M., Kurokawa K., Dean P., Kenny B., Quail M., Thurston S., Dougan G., Hayashi T., Parkhill J., Frankel G.
Journal of Bacteriology 91 ( 1 ) 347 - 354 2009年1月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Bacteriology
Enteropathogenic Escherichia coli (EPEC) was the first pathovar of E. coli to be implicated in human disease; however, no EPEC strain has been fully sequenced until now. Strain E2348/69 (serotype O127:H6 belonging to E. coli phylogroup B2) has been used worldwide as a prototype strain to study EPEC biology, genetics, and virulence. Studies of E2348/69 led to the discovery of the locus of enterocyte effacement-encoded type III secretion system (T3SS) and its cognate effectors, which play a vital role in attaching and effacing lesion formation on gut epithelial cells. In this study, we determined the complete genomic sequence of E2348/69 and performed genomic comparisons with other important E. coli strains. We identified 424 E2348/69-specific genes, most of which are carried on mobile genetic elements, and a number of genetic traits specifically conserved in phylogroup B2 strains irrespective of their pathotypes, including the absence of the ETT2-related T3SS, which is present in E. coli strains belonging to all other phylogroups. The genome analysis revealed the entire gene repertoire related to E2348/69 virulence. Interestingly, E2348/69 contains only 21 intact T3SS effector genes, all of which are carried on prophages and integrative elements, compared to over 50 effector genes in enterohemorrhagic E. coli O157. As E2348/69 is the most-studied pathogenic E. coli strain, this study provides a genomic context for the vast amount of existing experimental data. The unexpected simplicity of the E2348/69 T3SS provides the first opportunity to fully dissect the entire virulence strategy of attaching and effacing pathogens in the genomic context. Copyright © 2009, American Society for Microbiology. All Rights Reserved.
DOI： 10.1128/JB.01238-08
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Ogura Y., Abe H., Katsura K., Kurokawa K., Asadulghani M., Iguchi A., Ooka T., Nakayama K., Yamashita A., Hattori M., Tobe T., Hayashi T.
Journal of Bacteriology 190 ( 21 ) 6948 - 6960 2008年11月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Bacteriology
Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) are diarrheagenic pathogens that colonize the intestinal tract through the formation of attaching and effacing lesions, induced by effectors translocated via a type III secretion system (T3SS) encoded on the locus of enterocyte effacement (LEE). In EHEC O157, numerous virulence factors, including around 40 T3SS effectors, have been identified. Most of them are encoded on genomic islands (GEIs) such as prophages and integrative elements. For EPEC, however, no systematic search of GEIs and virulence-related genes carried therein has been done, and only a limited number of virulence factors have been identified so far. In this study, we performed a systemic and genome-wide survey of the GEIs in strain B171-8, one of the prototype strains of EPEC, by the combined use of whole-genome PCR scanning and fosmid mapping and identified 22 large GEIs, including nine lambda-like prophages, three P2-like prophages, the LEE, and three additional integrative elements. On these prophages and integrative elements, we found genes for a set of T3SS proteins, a total of 33 T3SS effectors or effector homologues, and 12 other virulence factors which include five nonfimbrial adhesins. Most of the T3SS effector families identified are also present in EHEC O157, but B171-8 possesses a significantly smaller number of effectors. Not only the presence or absence of Shiga toxin genes but also the difference in the T3SS effector repertoire should be considered in analyzing the pathogenicity of EPEC and EHEC strains. Copyright © 2008, American Society for Microbiology. All Rights Reserved.
DOI： 10.1128/JB.00625-08
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Iguchi A., Ooka T., Ogura Y., Asadulghani, Nakayama K., Frankel G., Hayashi T.
Microbiology 154 ( 2 ) 559 - 570 2008年2月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Microbiology
Typical enteropathogenic Escherichia coli (EPEC) O55:H7 is regarded as the closest relative of enterohaemorrhagic E. coli (EHEC) O157:H7. Both serotypes usually express the γ1 intimin subclass and trigger actin polymerization by the Tir-TccP pathway. However, atypical O55:H7 strains capable of triggering actin polymerization via the Tir-Nck pathway have recently been identified. In this study, we investigated the genotypic differences and phylogenetic relationships between typical and atypical O55:H7 strains. We show that the atypical O55:H7 strains, which express the θ intimin subclass and lack both tccP and tccP2, belong to an E. coli lineage distinct from the typical O55:H7 and from the EPEC O55:H6, which also uses the Tir-Nck actin polymerization pathway. We conducted genomic comparisons of the chromosomal regions covering the O-antigen gene cluster and its flanking regions between the three O55 lineages by RFLP analysis of PCR products and DNA sequencing analysis of about 65 kb chromosomal regions. This unexpectedly revealed that horizontal transfer of large fragments (≥40 kb) encoding the O55-antigen gene cluster and part of the neighbouring colanic acid gene cluster was involved in the emergence of the three O55 E. coli lineages. The data provide new insights into the mechanisms involved in the generation of a wide variety of O-serotypes in Gram-negative bacteria. © 2008 SGM.
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Iguchi A., Iyoda S., Watanabe H., Osawa R.
Current Microbiology 54 ( 1 ) 14 - 19 2007年1月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Current Microbiology
We investigated the relationship between expression of the O side chain of outer membrane lipopolysaccharide (LPS) and infection by a Shiga toxin 2 (Stx2)-converting phage in normal and benign strains of Escherichia coli. Of 19 wild-type E. coli strains isolated from the feces of healthy subjects, those with low-molecular-weight LPS showed markedly higher susceptibility to lytic and lysogenic infection by Stx2 phages than those with high-molecular-weight LPS. All lysogens produced infectious phage particles and Stx2. The Stx-negative E. coli O157:H7 strain ATCC43888 with an intact O side chain was found to be resistant to lysis by an Stx2 phage and lysogenic infection by a recombinant Stx2 phage, whereas a rfbE mutant deficient in the expression of the O side chain was readily infected by the phage and yielded stable lysogens. The evidence suggests that an O side chain deficiency leads to the creation of new pathotypes of Shiga toxin-producing E. coli (STEC) within the intestinal microflora. © 2006 Springer Science+Business Media, Inc.
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Iguchi A., Iyoda S., Terajima J., Watanabe H., Osawa R.
Gene 372 ( 1-2 ) 199 - 207 2006年5月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Gene
It is known that XbaI-digested chromosomal DNAs of strains of Escherichia coli O157:H7 exhibit a wide variety in pulsed-field gel electrophoresis (PFGE) fragment patterns, which is used for epidemiological surveillance of this important pathogen. The variety in the restriction enzyme-digestion patterns suggests a wide genomic diversity, however, only a few studies have been conducted to investigate involvement of large-scale chromosomal rearrangements in development of the diversity. In this study, through rounds of subculturing E. coli O157:H7 strain EDL933, naturally occurring genome variation in the isolated derivatives was investigated. By comparing the PFGE patterns among clonally related derivatives, we found five types of large-scale inversions taking place within the chromosome. The five inversions found were across the replication axis and ranged from 250-kb to 1.4-Mb long, and all the corresponding recombination sites were associated with prophages or phage-like regions. Four inversions out of the five were resulted from recombination between pairs of lambda-like prophages disturbing the symmetry of the origin and terminus of the replication axis. These observations indicate that those prophage regions represent some of the hot spots for intrachromosomal recombination within the E. coli O157:H7 chromosome, where recombination between the prophage regions results not only in the large chromosomal inversions but might also in generation of chimeric phages. © 2006 Elsevier B.V. All rights reserved.
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Okura M., Osawa R., Iguchi A., Takagi M., Arakawa E., Terajima J., Watanabe H.
Microbiology and Immunology 48 ( 10 ) 787 - 790 2004年
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Microbiology and Immunology
A PCR-based assay to identify pandemic group Vibrio parahaemolyticus has been developed. The assay employs an oligonucleotide primer pair derived from the group-specific sequence of an arbitrarily primed-PCR fragment, which is located in the genome encoding a "hypothetical protein," approximately 80% homologous to the Mn2+ and Fe2+ transporter of the NRAMP family of V. vulnificus. The assay distinguished the pandemic group from other V. parahaemolyticus strains by yielding a 235-bp specific amplicon, and can be a useful diagnostic tool for identification of pandemic group strains.
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Okura M., Osawa R., Iguchi A., Arakawa E., Terajima J., Watanabe H.
Journal of Clinical Microbiology 41 ( 10 ) 4676 - 4682 2003年10月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Clinical Microbiology
A total of 54 Vibrio parahaemolyticus strains including pandemic O3:K6 strains and newly emerged O4:K68, O1:K25, O1:K26, and O1:K untypeable strains (collectively referred to as the "pandemic group") were examined for their pulsed-field gel electrophoresis (PFGE) and arbitrarily primed PCR (AP-PCR) profiles and for the presence or absence of genetic marker DNA sequences, toxRS/new or orf8, that had been reported elsewhere to be specific for the pandemic group. Both PFGE and AP-PCR analyses indicated that all strains of the pandemic group formed a distinct genotypic cluster, suggesting that they originated from the same clone. In addition to the pandemic group, four O3:K6 strains that did not possess the thermostable direct hemolysin (tdh) gene also belonged to this cluster and possessed the toxRS/new sequence. However, three O3:K6 strains that clearly belonged to the pandemic group by PFGE and AP-PCR did not possess the orf8 sequence. The evidence suggests that neither the toxRS/new nor the orf8 sequence is a reliable gene marker for definite identification of the pandemic group. We therefore developed a novel multiplex PCR assay specific for the pandemic group. The assay successfully distinguished pandemic group strains from other V. parahaemolyticus strains by yielding two distinct PCR products for tdh (263 bp) and the toxRS/new sequence (651 bp).
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Sata S., Fujisawa T., Osawa R., Iguchi A., Yamai S., Shimada T.
Applied and Environmental Microbiology 69 ( 3 ) 1858 - 1860 2003年3月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Applied and Environmental Microbiology
An enrichment broth was developed for the efficient isolation of Escherichia coli O157 from radish sprouts. The broth was buffered peptone water containing 0.5% sodium thioglycolate (STG-BPW), which was designed to allow growth of E. coli O157 in starved and unstarved states. However, this medium suppressed the growth of non-carbohydrate-fermenting obligate aerobes whose colonial appearance on sorbitol MacConkey agar containing cefixime and tellurite (CT-SMAC) resembled that of E. coli O157. Both starved and unstarved cells of E. coli O157 experimentally inoculated into radish sprouts were successfully recovered with STG-BPW enrichment in all cases, most of which showed marked disappearance of E. coli O157-like colonies on CT-SMAC.
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Iguchi A., Osawa R., Kawano J., Shimizu A., Terajima J., Watanabe H.
Current Microbiology 46 ( 3 ) 224 - 227 2003年3月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Current Microbiology
Escherichia coli K-12 lysogens of three different Shiga toxin 2 (Stx2)-encoding bacteriophages were examined for variability in their pulsed-field gel electrophoresis (PFGE) fragment patterns. The PFGE fragment patterns could be classified into three types (i.e., PFGE types B, C, and D). For the PFGE type D, a 255-kbp fragment present in the original K-12 strain was apparently shifted by the size of Stx 2-encoding phage genomic DNA (ca. 65 kbp) to the position at 320 kbp. In contrast, the types B and C showed the above fragment shift plus further 6- and 10-fragment differences, respectively, from the original K-12 strain. The evidence suggests that even a single genetic event like lysogeny can cause marked genotypic modification of the host strain.
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Iguchi A., Osawa R., Kawano J., Shimizu A., Terajima J., Watanabe H.
Journal of Clinical Microbiology 40 ( 8 ) 3079 - 3081 2002年8月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Clinical Microbiology
Three clinical strains of enterohemorrhagic Escherichia coli O157:H7 which were subcultured repeatedly or stored at room temperature over a 25-week period showed appreciable variations in their pulsed-field gel electrophoresis fragment patterns. The variations could be explained by a couple of spontaneous genetic events at most and thus did not invalidate the genetic lineage of the strains.