Spontaneous chromosome rearrangements in the protozoan Giardia lamblia: estimation of mutation rates

Nucleic Acids Res. 1992 Sep 11;20(17):4539-45. doi: 10.1093/nar/20.17.4539.

Abstract

Subcloned lines of the WB strain of Giardia lamblia contain polymorphic ribosomal RNA (rRNA) encoding chromosomes (Le Blancq et al., Nucl. Acids Res. 1991, 19, 4405-4412). We show that in a continuously propagated culture of G.lamblia trophozoites the proportion of trophozoites with rearranged rRNA encoding chromosomes gradually increases, consistent with the high mutation rate of about 1% per cell per division cycle. This conclusion is based on the finding in one experiment that after about 8 division cycles 20% of the population consisted of independent mutants, while after approximately 100 division cycles 87.5% of the population were independent mutants. In a second experiment, approximately 38% and 71.5% of the trophozoites were independent mutants after approximately 9 and approximately 100 division cycles, respectively. The data show that the genome of the WB strain of G.lamblia has a highly recombinogenic phenotype. Extensive karyotype heterogeneity has also been observed among recently isolated G.lamblia strains obtained from a defined geographic area (Korman et al., J. Clin. Invest. 1992, 89, 1725-1733) suggesting that a high mutation rate might also occur in vivo.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Chromosomes / metabolism*
  • DNA Probes / genetics
  • DNA, Protozoan / metabolism*
  • DNA, Ribosomal / metabolism*
  • Electrophoresis, Gel, Pulsed-Field
  • Giardia lamblia / genetics*
  • Mathematics
  • Mutation / genetics
  • RNA, Ribosomal / genetics
  • Recombination, Genetic / genetics*

Substances

  • DNA Probes
  • DNA, Protozoan
  • DNA, Ribosomal
  • RNA, Ribosomal