Open AccessThe Size and Structure of the DNA Genome of Symbiont Xenosome Particles in the Ciliate Parauronema acutum
Author(s) -
A. T. Soldo,
S. A. Brickson,
F. S. Larin
Publication year - 1983
Publication title -
microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.019
H-Index - 179
eISSN - 1465-2080
pISSN - 1350-0872
DOI - 10.1099/00221287-129-5-1317
Subject(s) - ciliate , genome , genome size , dna , biology , extant taxon , bacteria , biophysics , chemistry , gene , genetics , evolutionary biology
The size and structure of the DNA genome of xenosomes, bacterial endosymbionts of the marine hymenostome ciliate, Parauronema acutum 110-3, were investigated. Renaturation kinetic measurements, determined optically and by hydroxyapatite chromatography, suggested a genome size of 0.34 x 10(9) daltons. Sedimentation rate measurements of DNA gently released from the symbionts yielded molecules of comparable size. The analytical complexity, determined chemically, was 3.03 x 10(9) daltons. Consistent with these and other data is a model for the structure of the symbiont genome in which the DNA exists in the form of nine circularly permuted, double-stranded DNA molecules of unique sequence, each of molecular weight 0.34 x 10(9). It is suggested that xenosomes and certain symbionts found in ciliated protozoa may be extant forms of once free-living bacteria that have adapted to the intracellular environment.