Construction of the mycoplasma evolutionary tree from 5S rRNA sequence data.

Abstract

The 5S rRNA sequences of eubacteria and mycoplasmas have been analyzed and a phylogenetic tree constructed. We determined the sequences of 5S rRNA from CMstridium innocuum, Acholeplasma laidlawii, Acholeplasma modicum, Anaeroplasma bactoclasticum, Anaeroplasma abactoclasticum, Ureaplasma urealyticum, Mycoplasma mycoides mycoides, Mycoplasma pneumoniae, and Mycoplasma gallisepticum. Analysis of these and published sequences shows that mycoplasmas form a coherent phylogenetic group that, with C. innocuum, arose as a branch of the low G+C Gram-positive tree, near the lactobacilli and streptococci. The initial event in mycoplasma phylogeny was formation of the Acholeplasma branch; hence, loss of cell wall probably occurred at the time of genome reduction to lO000 MDa. A subsequent branch produced the Spiroplasma. This branch appears to have been the origin of sterol-requiring mycoplasmas. During development of the Spiroplasma branch there were several independent genome reductions, each to -500 MDa, resulting in Mycoplasma and Ureaplasma species. Mycoplasmas, particularly species with the smallest genomes, have high mutation rates, suggesting that they are in a state of rapid evolution.The wall-less prokaryotes are grouped in the class Mollicutes and are referred to as mycoplasmas (1). Mycoplasma genera (Table 1) are diverse in terms of their biochemistry, ecological niches, and genome structure. In addition, some of these organisms are significant animal, plant, and insect pathogens. Two aspects of mycoplasma biology are of particular interest. First, some mycoplasmas (i.e., Spiroplasma, Mycoplasma, Ureaplasma, and some Anaeroplasma species) are the only prokaryotes known to require cholesterol for growth; and, second, mycoplasmas have the smallest amounts of genetic information of any free-living organisms. Mycoplasma DNAs contain a low percentage of G+C.Mycoplasma genomes fall into two size classes. Acholeplasma, Spiroplasma, and Thermoplasma genomes are "1000 MDa, a size that is rare but not unknown among eubacteria (reviewed in ref.2). Mycoplasma and Ureaplasma genomes are "500 MDa, the smallest reported cellular genomes. This is only slightly larger than the theoretical minimal amount of genetic information for a cellular system (4), indicating that the complexity of mycoplasma cells must be constrained by their limited genome content.The origin and phylogenetic relationships of mycoplasmas have been of interest because these cells are the result of natural selection operating within the constraint of limited genome complexity. In the past decade, a number of studies indicated that particular biochemical properties of some Mycoplasma and Acholeplasma species are closer to those of Gram-positive than to Gram-negative eubacteria (reviewed in refs. 2 and 3). A more complete view of mycoplasma evolution came from a recent comparative analysis of 16S rRNA oligonucleotide catalogs of Acholeplasma laidlawii, Spiroplasma citri, Mycoplasma capricolum, Mycoplasma gallisepticum, and Thermoplasma acidophilum with ...

Mycoplasma Gallisepticum strain S6 genome contains three regions hybridizing with 16 S rRNA and two regions hybridizing with 23 S and 5 S rRNA

“…Moreover, the length lisepticum was shown in [7]), of 5 S rRNA hybridizing fragments in Bg/II digest of We conclude that: there are two 23 S-5 S and three M. Gallisepticum DNA is identical to that of 23 S 16 S hybridizing regions in M. Gallisepticum genome.…”

“…Pilot exDeriments indicated that the hybridization patterns of digested M. Gallisepticum DNA with the orobes described are identical to that obtained utilizing-23 S rRNA or 16 S rRNA E. coli as probes. Oligonucleotide A01 (ACACCTGGTCC-CATTTCCGAACCC) synthesized according to pub1ishe:d sequence of 5 S RNA of M. Gallisepticum [7] was used as a nrobe for 5 S RNA.…”

Phylogenetic Diversity of Phytopathogenic Mycoplasmalike Organisms

“…Their genomes range in size from 680 to 1,600 kb (36). Previous analyses of 16s rRNA and 5s rRNA sequences have shown that members of the class Mollicutes are phylogenetically related to gram-positive bacteria (30,40,46,48). It has been postulated that the Mollicutes arose by degenerative evolution from clostridium-like ancestors.…”

Phylogeny and beyond: Scientific, historical, and conceptual significance of the first tree of life

“…Woese and his students determined several bacterial 5S rRNA sequences. They showed that the rRNA sequences could be used as phylogenetic markers for bacteria (15). They also showed that evolutionary variation in sequences could be used to determine how the RNAs fold into secondary structure (so-called phylogenetic comparative RNA structure analysis) (16).…”