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Tully et al., 1983
Mycoplasma genitalium is a small parasitic bacterium that lives on the ciliated epithelial cells of the primate genital and respiratory tracts. M. genitalium is the smallest known genome that can constitute a cell, and the second-smallest bacterium after the endosymbiont Carsonella ruddii. Until the discovery of Nanoarchaeum in 2002, M. genitalium was also considered to be the organism with the smallest genome.1 There is a difference between smallest parasitic bacteria and smallest free living bacteria. The smallest known free living bacterium is Pelagibacter ubique with 1.3 Mb.2
Mycoplasma genitalium was originally isolated in 1980 from urethral specimens of two male humans with non-gonococcal urethritis. Infection by M. genitalium seems fairly common, can be transmitted between partners during unprotected sexual intercourse, and can be treated with antibiotics; however, the organism's role in genital diseases is still unclear.
The genome of M. genitalium consists of 521 genes (482 protein encoding genes) in one circular chromosome of 582,970 base pairs. An initial study of the M. genitalium genome with shotgun sequencing was performed by Peterson in 1993. It was then sequenced by Fraser and others. It was found to contain only 470 predicted coding regions, including genes required for DNA replication, transcription and translation, DNA repair, cellular transport, and energy metabolism.3 It was the second complete bacterial genome ever sequenced, after Haemophilus influenzae. The small genome of M. genitalium made it the organism of choice in The Minimal Genome Project, a study to find the smallest set of genetic material necessary to sustain life.
Various symptoms of infection: An infected person may have some or all symptoms, or may be asymptomatic.
- Urethritis (in men)
- Discharge (both sexes)
- Burning while urinating (both sexes)
- Arthritis/reactive arthritis (mostly men)
- Vaginal itching (women)
- Pain during intercourse (women)
The Centers for Disease Control and Prevention in the United States recommend using4 one of these treatments, in this order of preference (the first is known to be the most effective, the others are alternative treatments)
- Azithromycin 1 g orally in a single dose
- Doxycycline 100 mg orally twice a day for 7 days
- Erythromycin base 500 mg orally four times a day for 7 days
- Erythromycin ethylsuccinate 800 mg orally four times a day for 7 days
- Ofloxacin 300 mg orally twice a day for 7 days
- Levofloxacin 500 mg orally once daily for 7 days
Studies have demonstrated that a 5 day course of Azithromycin has a superior cure rate than the 1 g single dose. Further, a 1 g single dose of Azithromycin can lead to the bacteria becoming resistant to Azithromycin.5 Based on these findings, UK doctors are moving to a 5 day Azithromycin regimen with 500 mg on day one and 250 mg on the subsequent four days. Doxycycline is also still used but Moxifloxacin is seen as an alternative treatment.6
In October 2007, a team of scientists headed by DNA researcher Craig Venter and Nobel laureate Hamilton Smith announced that they plan to create the first artificial life form in history by creating a synthetic chromosome, which they plan to inject into the M. genitalium bacterium, with potential to result in an artificial species dubbed Mycoplasma laboratorium or Mycoplasma JCVI-1.0 after the research centre in which it was created, the J. Craig Venter Institute in the United States.78
On 24 January 2008, the same team reported to have synthesized the complete 582,970-base pair genome of M. genitalium (a key gene that enables the wild organism to cause disease was knocked out). The final stage of synthesis was completed inside a M capricolum, which had its DNA removed, with the help of yeast cells (which were used to create the necessary DNA).9 On 20 May 2010 they reported success with a similar process, using instead the genome of Mycoplasma mycoides, creating what some called the first artificial life.10
On 20 July 2012, Stanford University and the J. Craig Venter Institute announced successful simulation of the complete life cycle of a Mycoplasma genitalium cell, in the journal Cell.11 The entire organism is modeled in terms of its molecular components, integrating all cellular processes into a single model. Using object oriented programming to model the interactions of 28 categories of molecules including DNA, RNA, proteins, and metabolites, and running on 128-core Linux cluster, the simulation takes 10 hours for a single M. genitalium cell to divide once — about the same time the actual cell takes — and generates half a gigabyte of data.12
- Arthritis / Reactive arthritis / Septic arthritis
- Candidatus Carsonella ruddii
- The Minimal Genome Project
- Aside from viruses—however, it is not agreed upon as to whether or not viruses constitute life.
- Stephen J. Giovannoni, H. James Tripp et al. (2005). "Genome Streamlining in a Cosmopolitan Oceanic Bacterium". Science 309 (5738): 1242–1245. doi:10.1126/science.1114057. PMID 16109880.
- Fraser, Claire M.; et al. (1995). "The Minimal Gene Complement of Mycoplasma genitalium". Science 270 (5235): 397–404. doi:10.1126/science.270.5235.397. PMID 7569993.
- Mycoplasma Genitalium Treatment Choices
- Pilkington, Ed (2007-10-06). "I am creating artificial life, declares US gene pioneer". The Guardian.
- Briggs, Helen (2008-01-24). "Synthetic life 'advance' reported". BBC News.
- Ball, Philip (2008-01-24). "Genome stitched together by hand". Nature News. doi:10.1038/news.2008.522.
- Swaby, Rachel. "Scientists Create First Self-Replicating Synthetic Life". Wired. Retrieved 21 May 2010.
- Jonathan R. Karr, Jayodita C. Sanghvi, Derek N. Macklin, Miriam V. Gutschow, Jared M. Jacobs, Benjamin Bolival, Nacyra Assad-Garcia, John I. Glass, Markus W. Covert (2012). "A Whole-Cell Computational Model Predicts Phenotype from Genotype". Cell (Elsevier) 150 (2): 389–401. Retrieved 20 July 2012.
- "In First, Software Emulates Lifespan of Entire Organism". The New York Times. 20 July 2012. Retrieved 2012-07-20.
- Mycoplasma genitalium Reference Work at the UK Health Protection Agency
- Mycoplasma genitalium G-37 genome page