Mycoplasma

Abstract

Abstract My.co.plas'ma. Gr. masc. n. mykês , mushroom or other fungus; Gr. neut. n. plasma , anything formed or molded, image, figure; N.L. neut. n. Mycoplasma , fungus form. Bacillota_I / Bacilli_A / Mycoplasmatales / Mycoplasmataceae / Mycoplasma Bacteria in the genus Mycoplasma are small (300–800 nm in diameter) pleomorphic cells devoid of a cell wall. Culturable species usually form very small (<1 mm) umbonate colonies on agar. Their use of the codon UGA to encode tryptophan is a distinctive characteristic of all species examined to date. As a consequence of their small (usually 0.5–1.5 Mb) genomes they have limited intermediary metabolism and are nutritionally fastidious, requiring exogenous carbohydrates or arginine, fatty acids, cholesterol or other sterols, peptides, cofactors, and free nucleic acids for axenic growth. In nature, all species are obligate commensals or parasites with varying degrees of specificity for a wide range of vertebrate hosts. The type species Mycoplasma mycoides subsp. mycoides and Mycoplasma capricolum subsp. capripneumoniae are highly virulent animal pathogens subject to strict international regulations, but the genus is perhaps better known for Mycoplasma pneumoniae , the agent of primary atypical “walking” pneumonia in humans. The relative biological simplicity of mycoplasmas confers significant advantages for current proteomics, metabolomics, synthetic genomics, and systems biology research. For example, the recent chemical synthesis and transplantation of intact chromosomes demonstrated that it is possible to enliven a mycoplasma fully capable of autonomous replication with an artificially constructed genome. DNA G + C content (mol%) : 23–40. Type species : Mycoplasma mycoides Freundt 1955 AL (basonym: Asterococcus mycoides Borrel et al. 1910.