Plasmid systems in Lyme
By Linda on Feb 1, 2011 in Infections | comments(0)
Excerpt:
The restriction-modification (R-M) systems of many bacteria present a
barrier to the stable introduction of foreign DNA. The Lyme disease
spirochete Borrelia burgdorferi has two plasmid-encoded putative R-M genes,
bbe02 and bbq67, whose presence limits transformation by shuttle vector DNA
from E. coli. We show that both the bbe02 and bbq67 loci in recipient B.
burgdorferi limit transformation with shuttle vector DNA from E. coli,
irrespective of its dam, dcm, or hsd methylation status. However, plasmid
DNA purified from B. burgdorferi transformed naive B. burgdorferi much more
efficiently than plasmid DNA from E.
coli, particularly when the bbe02 and bbq67 genotypes of the B. burgdorferi
DNA source matched that of the recipient. We detected adenine methylation of
plasmid DNA prepared from B. burgdorferi that carried bbe02 and bbq67. These
results indicate that the bbe02 and bbq67 loci of B. burgdorferi encode
distinct R-M enzymes that methylate endogenous DNA and cleave foreign DNA
lacking the same sequence-specific modification. Our findings have basic
implications for horizontal gene transfer among B. burgdorferi strains with
distinct plasmid contents. Further characterization and identification of
the nucleotide sequences recognized by BBE02 and BBQ67 will facilitate
efficient genetic manipulation of this pathogenic spirochete.
