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Restriction–modification system differences in Helicobacter pylori are a barrier to interstrain plasmid transfer
Author(s) -
Ando Takafumi,
Xu Qing,
Torres Melaine,
Kusugami Kazuo,
Israel Dawn A.,
Blaser Martin J.
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.02049.x
Subject(s) - biology , helicobacter pylori , plasmid , helicobacter , microbiology and biotechnology , genetics , gene
Helicobacter pylori cells are naturally competent for the uptake of both plasmid and chromosomal DNA. However, we demonstrate that there are strong barriers to transformation of H. pylori strains by plasmids derived from unrelated strains. We sought to determine the molecular mechanisms underlying these barriers. Transformation efficiency was assessed using pHP1, an Escherichia coli – H. pylori shuttle vector conferring kanamycin resistance. Transformation of 33 H. pylori strains was attempted with pHP1 purified from either E. coli or H. pylori , and was successfully introduced into only 11 strains. Digestion of H. pylori chromosomes with different restriction endonucleases (REs) showed that DNA methylation patterns vary substantially among strains. The strain most easily transformed, JP26, was found to have extremely low endogenous RE activity and to lack a restriction–modification (R–M) system, homologous to Mbo I, which is highly conserved among H. pylori strains. When we introduced this system to JP26, pHP1 from Mbo I.M + JP26, but not from wild‐type JP26, transformed Mbo I R − M + JP26 and heterologous Mbo I R − M + wild‐type H. pylori strains. Parallel studies with pHP1 from dam + and dam − E. coli strains confirmed these findings. These data indicate that the endogenous REs of H. pylori strains represent a critical barrier to interstrain plasmid transfer among H. pylori .