Genomic characterization of Helicobacter hepaticus: ordered cosmid library and comparative sequence analysis.
Helicobacter hepaticus is an important pathogen in laboratory mice and induces the development of liver tumors and gastrointestinal disease in susceptible strains of mice. In this study, a miniset of 36 cosmid clones from a genomic library of H. hepaticus was ordered and grouped into four large contigs representing approximately 1 Mb of the H. hepaticus genome using PCR, DNA sequencing, Southern and dot-blot hybridization and pulsed-field gel electrophoresis. From the 200-300 terminal nucleotide sequences of 38 cosmid clones, 56 coding regions were predicted, of which 51 were found to have orthologs in the public databases and five appeared to be unique to H. hepaticus. Of these 51 genes, 36 have orthologs in Helicobacter pylori and 25 display the highest sequence similarity to H. pylori. However, chromosomal positions of these genes are not conserved between these two helicobacters. In addition, 10 H. hepaticus genes had the highest sequence similarity to orthologs in Campylobacter jejuni. The GC content in a randomly selected 21-kb H. hepaticus genomic sequence was 35.8%, which approximates the average between H. pylori (39%) and C. jejuni (30.6%). These results demonstrate that: (1) H. hepaticus is more closely related to H. pylori than C. jejuni; (2) significant genomic alterations exist between H. hepaticus and H. pylori, including gene organization, protein sequences and GC content, probably in part due to specific adaptation to distinct ecological niches.
Ge
Z
Z
Division of Comparative Medicine, Massachusetts Institute of Technology, 16-873, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. zge@mit.edu
Feng
Y
Y
White
D A
DA
Schauer
D B
DB
Fox
J G
JG
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D020451:Contig Mapping; D003360:Cosmids / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D019143:Evolution, Molecular; D016680:Genome, Bacterial; D015698:Genomic Library; D016998:Helicobacter / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins