A new insertion sequence (IS) of Mycoplasma fermentans is described. This element, designated IS 1630 , is 1,377 bp long and has 27-bp inverted repeats at the termini. A single open reading frame (ORF), predicted to encode a basic protein of either 366 or 387 amino acids (depending on the start codon utilized), occupies most of this compact element. The predicted translation product of this ORF has homology to transposases of the IS 30 family of IS elements and is most closely related (27% identical amino acid residues) to the product of the prototype of the group, IS 30 . Multiple copies of IS 1630 are present in the genomes of at least two M. fermentans strains. Characterization and comparison of nine copies of the element revealed that IS 1630 exhibits unusual target site specificity and, upon insertion, duplicates target sequences in a manner unlike that of any other IS element. IS 1630 was shown to have the striking ability to target and duplicate inverted repeats of variable length and sequence during transposition. IS 30 -type elements typically generate 2- or 3-bp target site duplications, whereas those created by IS 1630 vary between 19 and 26 bp. With the exception of two recently reported IS 4 -type elements which have the ability to generate variable large duplications (B. B. Plikaytis, J. T. Crawford, and T. M. Shinnick, J. Bacteriol. 180:1037–1043, 1998; E. M. Vilei, J. Nicolet, and J. Frey, J. Bacteriol. 181:1319–1323, 1999), such large direct repeats had not been observed for other IS elements. Interestingly, the IS 1630 -generated duplications are all symmetrical inverted repeat sequences that are apparently derived from rho-independent transcription terminators of neighboring genes. Although the consensus target site for IS 30 is almost palindromic, individual target sites possess considerably less inverted symmetry. In contrast, IS 1630 appears to exhibit an increased stringency for inverted repeat recognition, since the majority of target sites had no mismatches in the inverted repeat sequences. In the course of this study, an additional copy of the previously identified insertion sequence IS Mi 1 was cloned. Analysis of the sequence of this element revealed that the transposase encoded by this element is more than 200 amino acid residues longer and is more closely related to the products of other IS 3 family members than had previously been recognized. A potential site for programmed translational frameshifting in IS Mi 1 was also identified.

The complete genome sequence of Mycoplasma hominis LBD-4 has been determined and the gene content ascribed. The 715,165-bp chromosome contains 620 genes, including 14 carried by a strain-variable prophage genome related to Mycoplasma fermentans MFV-1 and Mycoplasma arthritidis MAV-1. Comparative analysis with the genome of M. hominis PG21 ^T reveals distinctive arrangements of repeat-containing surface proteins.

Presented here is the complete and annotated genome sequence of Mycoplasma hominis Sprott (ATCC 33131). The chromosome comprises 695,214 bp, which is approximately 30 kb larger than the syntenic genome of M. hominis PG21 ^T . Tetracycline resistance of strain Sprott is most probably conferred by the tetM determinant, harbored on a mosaic transposon-like structure.

Intragenic tandem repeats occur throughout all domains of life and impart functional and structural variability to diverse translation products. Repeat proteins confer distinctive surface phenotypes to many unicellular organisms, including those with minimal genomes such as the wall-less bacterial monoderms, Mollicutes. One such repeat pattern in this clade is distributed in a manner suggesting its exchange by horizontal gene transfer (HGT). Expanding genome sequence databases reveal the pattern in a widening range of bacteria, and recently among eucaryotic microbes. We examined the genomic flux and consequences of the motif by determining its distribution, predicted structural features and association with membrane-targeted proteins.

Mycoplasma hyorhinis impacts swine health and production in many countries, either as a primary pathogen or as a component of a polymicrobial infection. Isolates of this species are also common contaminants of tissue culture lines. The genome sequence of the cell culture isolate M. hyorhinis GDL-1 is presented herein.