21097629
not annotated - annotated - LINNAEUS only
Genome copy numbers and gene conversion in methanogenic archaea.
Previous studies revealed that one species of methanogenic archaea, Methanocaldococcus jannaschii, is polyploid, while a second species, Methanothermobacter thermoautotrophicus, is diploid. To further investigate the distribution of ploidy in methanogenic archaea, species of two additional genera-Methanosarcina acetivorans and Methanococcus maripaludis-were investigated. M. acetivorans was found to be polyploid during fast growth (t(D) = 6 h; 17 genome copies) and oligoploid during slow growth (doubling time = 49 h; 3 genome copies). M. maripaludis has the highest ploidy level found for any archaeal species, with up to 55 genome copies in exponential phase and ca. 30 in stationary phase. A compilation of archaeal species with quantified ploidy levels reveals a clear dichotomy between Euryarchaeota and Crenarchaeota: none of seven euryarchaeal species of six genera is monoploid (haploid), while, in contrast, all six crenarchaeal species of four genera are monoploid, indicating significant genetic differences between these two kingdoms. Polyploidy in asexual species should lead to accumulation of inactivating mutations until the number of intact chromosomes per cell drops to zero (called "Muller's ratchet"). A mechanism to equalize the genome copies, such as gene conversion, would counteract this phenomenon. Making use of a previously constructed heterozygous mutant strain of the polyploid M. maripaludis we could show that in the absence of selection very fast equalization of genomes in M. maripaludis took place probably via a gene conversion mechanism. In addition, it was shown that the velocity of this phenomenon is inversely correlated to the strength of selection.
Ann file
T1 Species 43 63 methanogenic archaea
N1 Reference T1 Taxonomy:198240
T2 Species 112 132 methanogenic archaea
N2 Reference T2 Taxonomy:198240
T3 Species 134 163 Methanocaldococcus jannaschii
N3 Reference T3 Taxonomy:2190
T4 Species 203 242 Methanothermobacter thermoautotrophicus
N4 Reference T4 Taxonomy:145262
T5 Species 309 329 methanogenic archaea
N5 Reference T5 Taxonomy:198240
T6 Species 364 390 Methanosarcina acetivorans
N6 Reference T6 Taxonomy:2214
T7 Species 395 420 Methanococcus maripaludis
N7 Reference T7 Taxonomy:39152
T8 Species 440 454 M. acetivorans
N8 Reference T8 Taxonomy:2214
T9 Species 606 620 M. maripaludis
N9 Reference T9 Taxonomy:39152
T10 Species 1487 1501 M. maripaludis
N10 Reference T10 Taxonomy:39152
T11 Species 1586 1600 M. maripaludis
N11 Reference T11 Taxonomy:39152
#1 AnnotatorNotes T1 TODO check
#2 AnnotatorNotes T2 TODO check
#3 AnnotatorNotes T5 TODO check