Download 93134006蔡家妮 期中作業二

期中作業二
第一篇
作者：William S. Jermyn and E. Fidelma Boyd
題目：Molecular evolution of Vibrio pathogenicity island-2 (VPI-2): mosaic
structure among Vibrio cholerae and Vibrio mimicus natural isolates
出處： Microbiology 卷數？頁數？
年份：２００５
摘要：Vibrio cholerae is a Gram-negative rod that inhabits the aquatic environment
and is the aetiological agent of cholera, a disease that is endemic in much of Southern
Asia. The 57·3 kb Vibrio pathogenicity island-2 (VPI-2) is confined predominantly to
toxigenic V. cholerae O1 and O139 serogroup isolates and encodes 52 ORFs
(VC1758 to VC1809), which include homologues of an integrase (VC1758), a
restriction modification system, a sialic acid metabolism gene cluster (VC1773–
VC1783), a neuraminidase (VC1784) and a gene cluster that shows homology to Mu
phage. In this study, a 14·1 kb region of VPI-2 comprising ORFs VC1773 to VC1787
was identified by PCR and Southern blot analyses in all 17 Vibrio mimicus isolates
examined. The VPI-2 region in V. mimicus was inserted adjacent to a serine tRNA
similar to VPI-2 in V. cholerae. In 11 of the 17 V. mimicus isolates examined, an
additional 5·3 kb region encoding VC1758 and VC1804 to VC1809 was present
adjacent to VC1787. The evolutionary history of VPI-2 was reconstructed by
comparative analysis of the nanH (VC1784) gene tree with the species gene tree,
deduced from the housekeeping gene malate dehydrogenase (mdh), among V.
cholerae and V. mimicus isolates. Both gene trees showed an overall congruence; on
both gene trees V. cholerae O1 and O139 serogroup isolates clustered together,
whereas non-O1/non-O139 serogroup isolates formed separate divergent branches
with similar clustering of strains within the branches. One exception was noted: on the
mdh gene tree, V. mimicus sequences formed a distinct divergent lineage from V.
cholerae sequences; however, on the nanH gene tree, V. mimicus clustered with V.
cholerae non-O1/non-O139 isolates, suggesting horizontal transfer of this region
between these species.
第二篇
作者：W. M. A. von Krügera,1, S. Humphreysb,2 and J. M. Ketley1
題目：A role for the PhoBR regulatory system homologue in the Vibrio cholerae
phosphate-limitation response and intestinal colonization
出處： Microbiology 卷數？頁數？
年份：１９９９
摘要：To survive and multiply in different environments, Vibrio cholerae has to coordinately regulate the expression of genes involved in adaptive responses. In many
pathogens, adaptive responses, including pathogenic responses, are regulated by twocomponent regulator (TCR) systems. It is likely that members of a TCR family play a
role in the regulation of processes involved in intestinal colonization, and therefore
pathogenesis, in V. cholerae. We have identified and characterized a TCR system of V.
cholerae: this system is a homologue of Escherichia coli PhoBR. The presence of a
putative Pho box suggests that the V. cholerae phoBR operon is regulated by
inorganic phosphate levels. The phoR and phoB genes are organized the same way as
in E. coli. Mutation of the V. cholerae phoB gene affected the expression of the
putative Pho regulon, including PhoA, but did not affect the production of cholera
toxin. V. cholerae phoB mutants are less able to colonize rabbit intestine than wildtype V. cholerae. The addition of inorganic phosphate at a high concentration to the
inoculum only partially restored the ability of the mutants to colonize the intestine,
suggesting that the V. cholerae Pho regulon in vivo may not be regulated by inorganic
phosphate levels alone.
第三篇
作者：M. Farfán1, D. Miñana1, M. C. Fusté1 and J. G. Lorén1
題目：Genetic relationships between clinical and environmental Vibrio cholerae
isolates based on multilocus enzyme electrophoresis
出處： Microbiology 卷數？頁數？
年份：２０００
摘要：A total of 107 isolates of Vibrio cholerae, including 29 strains belonging to
serogroup O139, were studied using multilocus enzyme electrophoresis (MLEE) to
determine allelic variation in 15 housekeeping enzyme loci. All loci were
polymorphic and 99 electrophoretic types (ETs) were identified from the total sample.
No significant clustering of isolates was detected in the dendrogram generated from a
matrix of coefficients of distances with respect to serogroup, biotype or country of
isolation. The mean genetic diversity of this V. cholerae population (H=0·50) was
higher than reported previously. Linkage disequilibrium analysis of the MLEE data
showed a clonal structure for the entire population, but not in some of the population
subgroups studied. This suggests an epidemic population structure. The results
showed that the O139 strains were not clustered in a unique ET, in contrast to previous
MLEE studies. This higher genetic variation of the O139 serogroup is concordant with
ribotyping studies. The results also confirm that the O139 and O1 ElTor isolates are
genetically more closely related to each other than to all the other subpopulations of V.
cholerae stud
第四篇
作者：Sanjib Banerjee and Rukhsana Chowdhury
題目：An orphan DNA (cytosine-5-)-methyltransferase in Vibrio cholerae
出處： Microbiology 卷數？頁數？
年份：２００６
摘要：5-Methyl cytosine (m5C) was detected in genomic DNA of the enteric
pathogen Vibrio cholerae by HPLC analysis and immunoblotting with m5C-specific
antibody. Although cleavage with the restriction endonuclease EcoRII revealed the
absence of a Dcm homologue in V. cholerae, analysis of the genome sequence
indicated the presence of a gene, designated in this study as vchM, which encodes a
DNA (cytosine-5-)-methyltransferase (m5C-MTase) designated M.Vch. M.Vch is not
associated with a restriction endonuclease or a mismatch very short patch repair (Vsr)like endonuclease and is hence an ‘orphan’ or solitary MTase, although analysis of a
phylogenetic tree indicated that related cytosine MTases are all components of
restriction-modification systems. M.Vch recognizes and methylates the first 5' C in
the degenerate sequence 5'-RCCGGY-3'. RT-PCR analysis suggested that vchM gene
expression is increased during the stationary phase of growth. During stationary phase,
the spontaneous mutation frequency in the V. cholerae wild-type strain was
significantly higher than in the corresponding vchM mutant strain, suggesting that the
presence of M.Vch and the absence of a very short patch (VSP) repair-like system
imposes upon V. cholerae a mutator phenotype.
第五篇
作者：ME Kovach, MD Shaffer and KM Peterson
題目：A putative integrase gene defines the distal end of a large cluster of ToxRregulated colonization genes in Vibrio cholerae
出處： Microbiology
年份：１９９６
摘要：A large cluster of virulence genes encoding proteins involved in Vibrio
cholerae accessory colonization factor (ACF) expression and toxin- coregulated pilus
(TCP) biogenesis is flanked by sequences that resemble bacteriophage attachment (att)
half-sites. Adjacent to the attL-like site is a gene (int) that encodes a protein related to
the integrase family of site-specific recombinases. The putative vibrio integrase
appears to be most closely related to the Escherichia coli cryptic prophage (CP4-57)
integrase protein (52% identity, 73% similarity). Genomic analysis of numerous V.
cholerae strains (O1, non- O1 and O139) revealed that only vibrios capable of
causing epidemic Asiatic cholera possess the TCP-ACF colonization gene cluster in
association with the integrase. The fact that the integrase gene is absent in avirulent
strains suggests that epidemic strains of V. cholerae obtained the TCP-ACF
colonization gene cluster via horizontal transfer.