GENOME SIZE AND LIFE CYCLE OF THE MYCOPLASMA*
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ABSTRACT: The concept of a minimal cell is discussed from the viewpoint of comparative genomics. Analysis of published DNA content values determined for 641 different archaeal and bacterial species by pulsed field gel electrophoresis has lead to a more precise definition of the genome size ranges of free-living and host-associated organisms. DNA content is not an indicator of phylogenetic position. However, the smallest genomes in our sample do not have a random distribution in rRNA-based evolutionary trees, and are found mostly in (a) the basal branches of the tree where thermophiles are located; and (b) in late clades, such as those of Gram positive bacteria. While the smallest-known genome size for an endosymbiont is only 450 kb, no free-living prokaryote has been described to have genomes < 1450 kb. Estimates of the size of minimal gene complement can provide important insights in the primary biological functions required for a sustainable, reproducing cell nowadays and throughout evolutionary times, but definitions of the minimum cell is dependent on specific environments.Origins of Life and Evolution of Biospheres 02/2004; 34(1-2):243-56. DOI:10.1023/B:ORIG.0000009844.90540.52 · 1.77 Impact Factor
- In Vitro Cellular & Developmental Biology - Plant 01/1984; 20(1):1-18. DOI:10.1007/BF02633326 · 1.16 Impact Factor
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ABSTRACT: Serological techniques are recommended procedures for the identification of Mycoplasma species. They enable separation of mycoplasmas at the species level and are widely used for practical laboratory identification of the isolated microorganisms. However, complex growth media are required for the isolation of Mycoplasma species and some strains of pathogenic Mycoplasma species grow very fastidious and can not be cultured. Introduction of DNA based diagnostic methods in mycoplasma research enabled survey of the whole genome in a single assay and reveal also information about non- coding regions of the genome. Restriction enzyme analysis is a powerful method for differentiation of close related strains but requires high quality of DNA which can only be obtained from cultured mycoplasmas. The increasing number of cloned mycoplasma genomic fragments are successfully used for identification and differentiation of mycoplasma strains and species in hybridization studies. The polymerase chain reaction enables identification and characterization of mycoplasmas without culture directly from clinical material. Large genomic sequencing projects produced complete nucleotide sequence from two Mycoplasma species and several more are in progress. This data will open the possibility to understand better the biology of mycoplasmas.