Genome analysis-based union of the genus Mesoplasma with the genus Entomoplasma.

Early characterization of strains designated into the genera Entomoplasma and Mesoplasma was based upon biological and chemical characteristics. With the advent of 16S rRNA gene sequence analysis as an added taxonomic character, it became clear that the two genera did not form distinct and separate monophyletic clusters. A genome-level analysis of all 17 validly published species within the family Entomoplasmataceae has recently been performed. Phylogenetic analyses, comparisons of gene content, and the lack of genus-specific genes supported that species from the two genera are intermixed and should not be taxonomically separated. This level of analysis clearly reveals the necessity to revise the taxonomy of this family by merging the two genera into one, Entomoplasma. Additionally, it was definitively determined that the strain originally designated as Acholeplasma multilocale resides in this cluster and should be formally renamed as Entomoplasma multilocale. Merging Mesoplasma and Entomoplasma yields a paraphyletic genus, but is supported by cell morphology and ecology to be distinguished from the genera Spiroplasma and Mycoplasma.

Probabilistic inference of lateral gene transfer events.

BACKGROUND: Lateral gene transfer (LGT) is an evolutionary process that has an important role in biology. It challenges the traditional binary tree-like evolution of species and is attracting increasing attention of the molecular biologists due to its involvement in antibiotic resistance. A number of attempts have been made to model LGT in the presence of gene duplication and loss, but reliably placing LGT events in the species tree has remained a challenge. RESULTS: In this paper, we propose probabilistic methods that samples reconciliations of the gene tree with a dated species tree and computes maximum a posteriori probabilities. The MCMC-based method uses the probabilistic model DLTRS, that integrates LGT, gene duplication, gene loss, and sequence evolution under a relaxed molecular clock for substitution rates. We can estimate posterior distributions on gene trees and, in contrast to previous work, the actual placement of potential LGT, which can be used to, e.g., identify "highways" of LGT. CONCLUSIONS: Based on a simulation study, we conclude that the method is able to infer the true LGT events on gene tree and reconcile it to the correct edges on the species tree in most cases. Applied to two biological datasets, containing gene families from Cyanobacteria and Molicutes, we find potential LGTs highways that corroborate other studies as well as previously undetected examples.

Reclassification of Mesoplasma pleciae as Acholeplasma pleciae comb. nov. on the basis of 16S rRNA and gyrB gene sequence data.

Genomic DNA sequence data for the 16S rRNA gene and the gyrB gene of Mesoplasma pleciae PS-1(T) (=ATCC 49582(T)=NBRC 100476(T)) demonstrate a much closer relationship to Acholeplasma laidlawii and Acholeplasma oculi than to other species in the order Entomoplasmatales. In addition, the preferred use of UGG rather than UGA as the codon for tryptophan in the gyrB sequence probably places the organism outside the order Entomoplasmatales. It is proposed that M. pleciae be reclassified in the genus Acholeplasma, as Acholeplasma pleciae comb. nov.