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NORTH CAROLINA RESEARCHERS
DISCUSS LYME'S 25 PLASMIDS

PLASMIDS ARE GENES SHARED AMOUNG LYME SPIROCHETES
WHICH INCREASE SURVIVAL AND RESISTENCE TO ANTIBIOTICS

First, you should know the definition of a plasmid:
A plasmid is a strand or loop of DNA material that exists independently of the chromosome in bacteria and yeast. In addition it is capable of genetic replication. Further, it used by some bacteria to spread antibiotic resistance genes and by biologists to insert foreign genes into cells.

Role of Borrelia burgdorferi linear plasmid 25 in infection of Ixodes scapularis ticks.

Department of Microbiology and Immunology, CB no. 7290, University of North Carolina, Chapel Hill, NC 27599, USA.

The tick-borne bacterium Borrelia burgdorferi has over 20 different circular and linear plasmids. Some B. burgdorferi plasmids are readily lost during in vitro culture or genetic manipulation. Linear plasmid 25, which is often lost in laboratory strains, is required for the infection of mice. Strains missing linear plasmid 25 (lp25(-)) are able to infect mice if the BBE22 gene on lp25 is provided on a shuttle vector. In this study, we examined the role of lp25 and BBE22 in tick infections. We tested the hypothesis that complementation with BBE22 in spirochetes lacking lp25 would restore the ability of spirochetes to infect ticks. A natural tick infection cycle was performed by feeding larvae on mice injected with the parental, lp25(-), or lp25(-) BBE22-complemented spirochete strains. In addition, larvae and nymphs were artificially infected with different strains to study tick infections independent of mouse infections. B. burgdorferi missing lp25 was significantly impaired in its ability to infect larval and nymphal ticks. When an lp25(-) strain was complemented with BBE22, the ability to infect ticks was partially restored. Complementation with BBE22 allowed spirochetes lacking lp25 to establish short-term infections in ticks, but in most cases the infection prevalence was lower than that of the wild-type strain. In addition, the number of infected ticks decreased over time, suggesting that another gene(s) on lp25 is required for long-term persistence in ticks and completion of a natural infection cycle.

JOURNAL OF BACTERIOLOGY. 2005 Aug;187(16):5776-81.
Strother KO, de Silva A.
PMID: 16077125 [PubMed - indexed for MEDLINE]


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