Mesoplasma florum
Classification
Higher order taxa
Bacteria; Firmicutes; Mollicutes; Entomoplasmatales; Entomoplasmataceae; Mesoplasma
Species
Mesoplasma florum
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NCBI: Taxonomy |
Description and significance
Mesoplasma florum is a Mycoplasma species, which come from the bacteria Mollicutes. Mollicutes do not have a cell wall and are parasitic to humans, animals, and plants. Mycoplasma are characteristically small, as well as self-replicating. Although Mesoplasma florum are a species of Mycoplasma, Mesoplasma florum are not parasitic and are non-motile, unlike Mycoplasma. Like Mycoplasma, Mesoplasma florum are also have a very small genome size (smaller than 1Mb). (1) Mesoplasma florum was isolated from the flower of a lemon tree, and is therefore thought to be associated with plant insect vectors. (5)
Gene sequencing of Mesoplasma florum is important because it is the smallest self-replicating organism, Mycoplasma, and therefore, is itself very small. Furthermore, Micoplasma florum is non-motile, so it is used to study and identify genes that are linked to motility.(1) Researchers working with Mesoplasma florum can use this species to understand why it has evolved to be non-motile even though Mycoplasma are motile, as well as why it has evolved to become non-parasitc. This shows us that Mycoplasma are highly evolving, and therefore are highly successful, therefore, gene sequencing of Mesoplasma florum is important because it is important in learning as to why Mesoplasma florum have evolved the way that it has. (2) As a result of their small genomes, they do not have a lot of metabolic ability. (2) They can easily adapt to their environment, even if that environment is changing. (1) This is important because Mesoplasma florum, as well as all species of Mycoplasma, uptake their nutrients from their environment. (3) Therefore, it is important to understand why this organism can thrive by uptaking nutrients which are continually changing.
Mesoplasma florum is not closely related to Mycoplasma genitalium and Mycoplasma pneumoniae. Although sterol is required in media for growth of Mollicutes, Mesoplasma florum does not require sterol. (1)
Genome structure
M. florum has a uniquely small genome size (smaller than 1Mb), due to its evolution from Mycoplasmas, which evolved from Gram-positive bacteria by reducing genome size many times. Mesoplasma florum has another unique genome characteristic in that in Mycoplasmas, the stop codon, UGA, has been changed to be translated as tryptophan. (1) (See Current research for further information).
Currently, genome sequencing for M. florum is being performed by Tom Knight, Senior Research Scientist at the MIT Artificial Intelligence Laboratory and the MIT Electrical Engineering and Computer Science Department, and the Broad Institute of MIT and Harvard. The Mesoplasma florum project will eventually yield gene discovery and further analysis of this species. The M. florum genome has been fully annotated. The method employed for sequencing the genome was Whole Genome Shotgun, where DNA is isolated from M. florum and cut into smaller fragments. These DNA fragments are then inserted into and vector and cloned, and both ends of the DNA fragments are sequenced, which produces paired reads. The paired reads are used to identify contigs, (contiguous stretches of sequence) which are ordered into supercontigs. (1)
M. florum has a circular genome that is 793,224 bp in size. It has a G+C content of 27.02%. (1) In M. florum, UGA encodes tryptophan in the rsp3 gene. (4) This bacterium has only 682 genes.
Cell structure and metabolism
Because of their small genome structure, M. florum have limited metabolic and biosynthetic capacity. This is because of its evolution from cell-walled gram-positive Firmicutes, which have a low G+C content. As the Mollicutes evolved, (including M. florum) they increasingly become smaller in size, thus they evolved toward a small genome size, thus making itself dependent on the nutrients that its environment provides. This evolution toward small size is the reason why Mollicutes, as well as M. florum, have lost many of the genes that are involved in biosynthesis of lipids, amino acids, cofactors, and and gram-positive type cell wall components, as well as genes involved in transcription regulation, heat shock response, and cell division. Furthermore, they are deficient intermediate energy metabolism, and therefore depend on glycolysis as a source of ATP. The ATP can be synthesized via the glycolytic pathway or lactic fermentation. The above mentioned deficiencies are why M. florum depend so heavily on its surroundings as a source of nutrients. The reduction in size of the genome was heavily due to the above mentioned loss of metabolic pathways. (6)
For Mollicutes, cholesterol is a requirement for growth. (6) Sugars are used as a source of carbon and for energy for glycolysis. Furthermore, the pentose phosphate pathway is incomplete in Mollicutes. However, genes the encode enzymes of the tricarboxylic acid cycle are absent from the genomes. (7)
Ecology
Mesoplasma florum was originally recovered from the flower of a lemon tree. (5) M. florum is associated with plant insect vectors. However, its primary vector has not yet been identified. (1)
Pathology
Mesoplasma florum is non-pathogenic, and therefore there are no known diseases that are related to this organism.
