Mycoplasma Genomes Research Articles

Pulsed-field electrophoresis indicates larger-than-expected sizes for mycoplasma genomes.

The sizes of large DNA fragments produced from genomes of members of the Mycoplasmataceae by digestion with restriction endonucleases having infrequent (1 to 3) cleavage sites within the genome were estimated from their mobility in contour-clamped homogeneous electric field (CHEF) agarose gel electrophoresis by comparison with yeast chromosomal DNA markers. The estimates of total genome size for 7 strains of 6 species ranged from approximately 900 kilo base pairs (kb) for Ureaplasma urealyticum 960T to 1330 kb for M. mycoides subsp. mycoides, GC-1176. The values derived from this new method are considerably higher than those of approximately 500 Mdaltons or 750 kb previously reported for genome sizes in members of the Mycoplasmataceae.

Repetitive DNA sequences in Mycoplasma pneumoniae.

Two types of different repetitive DNA sequences called RepMP1 and RepMP2 were identified in the genome of Mycoplasma pneumoniae. The number of these repeated elements, their nucleotide sequence and their localization on a physical map of the M. pneumoniae genome were determined. The results show that RepMP1 appears at least 10 times and RepMP2 at least 8 times in the genome. The repeated elements are dispersed on the chromosome and, in three cases, linked to each other by a homologous DNA sequence of 400 bp. The elements themselves are 300 bp (for RepMP1) and 150 bp (for RepMP2) long showing a high degree of homology. One copy of RepMP2 is a translated part of the gene for the major cytadhesin protein P1 which is responsible for the adsorption of M. pneumoniae to its host cell.

Novel codon-anticodon recognition patterns in Mycoplasma capricolum.

The tRNA anticodon list for an extremely AT-rich bacterium, Mycoplasma capricolum, is unique and may be characterized by (1) removal of all the non-obligate CNN anticodons, (2) the presence of UNN (U, unmodified) anticodons in all family boxes, except arginine family box, (3) appearance of anticodon AGU for threonine colon ACU, (4) removal of GNN anticodons from family boxes, (5) occurrence of arginine anticodon ICG as in other bacteria and yet probable disappearance of anticodon CCG from arginine family box that would have resulted in CGG colon unassigned, and (6) development of anticodon *UCA that has led to the use of the universal stop colon UGA as a tryptophan colon. The above-mentioned deviation of the genetic code in Mycoplasma from the codes in other eubacteria, such as in E. coli and B. subtilis, may be explained by strong AT-directional mutation pressure that has been exerted to the Mycoplasma genome.