Mycoplasma
Encyclopedia
Mycoplasma refers to a genus
of bacteria
that lack a cell wall
. Without a cell wall, they are unaffected by many common antibiotics such as penicillin
or other beta-lactam
antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogen
ic in humans, including M. pneumoniae
, which is an important cause of atypical pneumonia
and other respiratory disorders, and M. genitalium
, which is believed to be involved in pelvic inflammatory diseases. Mycoplasma is the smallest known cell and is about 0.1 μ micron in diameter.
An older name for Mycoplasma was Pleuropneumonia-Like Organisms (PPLO), referring to organisms similar to the causative agent of contagious bovine pleuropneumonia
(CBPP). It was later found that the fungus-like growth pattern of M. mycoides is unique to that species.
Mollicutes
. Mollicutes are parasites or commensals of humans, other animals (including insects), and plants; the genus Mycoplasma is by definition restricted to vertebrate
hosts. Cholesterol
is required for the growth of species of the genus Mycoplasma as well as certain other genera of mollicutes. Their optimum growth temperature is often the temperature of their host if warmbodied (e. g. 37° C
in humans) or ambient temperature if the host is unable to regulate its own internal temperature. Analysis of 16S ribosomal RNA
sequences as well as gene
content strongly suggest that the mollicutes, including the mycoplasmas, are closely related to either the Lactobacillus
or the Clostridium
branch of the phylogenetic tree (Firmicutes
sensu stricto).
of the genus Mycoplasma (trivial name: mycoplasmas) and their close relatives are characterized by lack of a cell wall
. Despite this, the cells often present a certain shape, with a characteristic small size, with typically about 10% of the volume of an Escherichia coli
cell. These cell shapes presumably contribute to the ability of mycoplasmas to thrive in their respective environments. Most are pseudococcoidal, but there are notable exceptions. Species of the M. fastidiosum cluster are rod-shaped. Species of the M. pneumoniae cluster, including M. pneumoniae
, possess a polar extension protruding from the pseudococcoidal cell body. This tip structure, designated an attachment organelle or terminal organelle, is essential for adherence to host cells and for movement along solid surfaces (gliding motility), and is implicated in normal cell division. M. pneumoniae cells are pleomorphic, with an attachment organelle of regular dimensions at one pole and a trailing filament of variable length and uncertain function at the other end, whereas other species in the cluster typically lack the trailing filament. Other species like M. mobile and M. pulmonis have similar structures with similar functions.
Mycoplasmas are unusual among bacteria in that most require sterols for the stability of their cytoplasmic membrane. Sterols are acquired from the environment, usually as cholesterol from the animal host. Mycoplasmas generally possess a relatively small genome
of 0.58-1.38 megabases, which results in drastically reduced biosynthetic capabilities and explains their dependence on a host. Additionally they use an alternate genetic code
where the codon UGA is encoding for the amino acid tryptophan
instead of the usual opal stop codon
. They have a low GC-content
(23-40 mol
%).
subsp. mycoides SC (small-colony type), and the work of Nocard and Roux represented the first isolation of a mycoplasma species. Cultivation was, and still is difficult because of the complex growth requirements.
These researchers succeeded by inoculating a semi-permeable pouch of sterile medium with pulmonary fluid from an infected animal and depositing this pouch intraperitoneally into a live rabbit. After fifteen to twenty days, the fluid inside of the recovered pouch was opaque, indicating the growth of a microorganism. Opacity of the fluid was not seen in the control. This turbid broth could then be used to inoculate a second and third round and subsequently introduced into a healthy animal, causing disease. However, this did not work if the material was heated, indicating a biological agent at work. Uninoculated media in the pouch, after removal from the rabbit, could be used to grow the organism in vitro
, demonstrating the possibility of cell-free cultivation and ruling out viral causes, although this was not fully appreciated at the time .
and genomics
have brought the genetically simple mycoplasmas, particularly M. pneumoniae and its close relative M. genitalium
, to a larger audience. The second published complete bacterial genome sequence was that of M. genitalium, which has one of the smallest genomes of free-living organisms. The M. pneumoniae genome sequence was published soon afterwards and was the first genome sequence determined by primer walking
of a cosmid
library instead of the whole-genome shotgun method. Mycoplasma genomics and proteomics
continue in efforts to understand the
so-called minimal cell
, catalog the entire protein content of a cell, and generally continue to take advantage of the small genome of these organisms to understand broad biological concepts.
, and small subunit rRNA
gene and whole genome sequencing. A recent focus in the sub-discipline of molecular phylogenetics has both clarified and confused certain aspects of the organization of the class Mollicutes.
Originally the trivial name "mycoplasmas" has commonly denoted all members of the class Mollicutes
. The name "Mollicutes" is derived from the Latin mollis (soft) and cutes (skin), and all of these bacteria do lack a cell wall and the genetic capability to synthesize peptidoglycan
. Now Mycoplasma is a genus in Mollicutes. Despite the lack of a cell wall, many taxonomists have classified Mycoplasma and relatives in the phylum Firmicutes
, consisting of low G+C Gram-positive bacteria such as Clostridium
, Lactobacillus
, and Streptococcus
based on 16S rRNA gene analysis. The order Mycoplasmatales contains a single family, Mycoplasmataceae
, comprising two genera: Mycoplasma and Ureaplasma
.
Historically, the description of a bacterium lacking a cell wall was sufficient to classify it to the genus Mycoplasma and as such it is the oldest and largest genus of the class with about half of the class' species (107 validly described), each usually limited to a specific host and with many hosts harboring more than one species, some pathogenic and some commensal. In later studies, many of these species were found to be phylogenetically distributed among at least three separate orders.
A limiting criterion for inclusion within the genus Mycoplasma is that the organism have a vertebrate host. In fact, the type species, M. mycoides
, along with other significant mycoplasma species like M. capricolum, is evolutionarily more closely related to the genus Spiroplasma
in the order Entomoplasmatales than to the other members of the Mycoplasma genus. This and other discrepancies will likely remain unresolved because of the extreme confusion that change could engender among the medical and agricultural communities.
The remaining species in the genus Mycoplasma are divided into three non-taxonomic groups, hominis, pneumoniae and fermentans, based on 16S rRNA gene sequences.
The hominis group contains the phylogenetic clusters of M. bovis, M. pulmonis, and M. hominis
, among others. M. hyopneumoniae
is a primary bacterial agent of the porcine respiratory disease complex.
The pneumoniae group contains the clusters of M. muris, M. fastidiosum, U. urealyticum
, the currently unculturable haemotrophic mollicutes, informally referred to as haemoplasmas (recently transferred from the genera Haemobartonella and Eperythrozoon), and the M. pneumoniae cluster. This cluster contains the species (and the usual or likely host) M. alvi (bovine), M. amphoriforme (human), M. gallisepticum
(avian), M. genitalium
(human), M. imitans (avian), M. pirum (uncertain/human), M. testudinis (tortoises), and M. pneumoniae
(human). Most if not all of these species share some otherwise unique characteristics including an attachment organelle, homologs of the M. pneumoniae cytadherence-accessory proteins, and specialized modifications of the cell division apparatus.
A study of 143 genes in 15 species of Mycoplasma suggests that the genus can be grouped into four clades: the M. hyopneumoniae group, the M. mycoides group, the M. pneumoniae group and a Bacillus-Phytoplasma group. The M. hyopneumoniae group is more closely related to the M. pneumoniae group than the M. mycoides group.
. Mycoplasmal cell culture contamination occurs due to contamination from individuals or contaminated cell culture medium ingredients. Mycoplasma cells are physically small – less than 1 µm – and they are therefore difficult to detect with a conventional microscope
. Mycoplasmas may induce cellular changes, including chromosome
aberrations, changes in metabolism
and cell growth. Severe Mycoplasma infections may destroy a cell line. Detection techniques include DNA Probe, enzyme immunoassays
, PCR
, plating on sensitive agar
and staining with a DNA
stain including DAPI
or Hoechst
.
It has been estimated that at least 11 to 15% of U.S. laboratory cells cultures are contaminated with mycoplasma.
A Corning study showed that half of U.S. scientists did not test for mycoplasma contamination in their cell cultures. The study also stated that, in Czechoslovakia, 100% of cell cultures that were not routinely tested were contaminated while only 2% of those routinely tested were contaminated. (study page 6) Since the U.S. contamination rate was based on a study of companies that routinely checked for mycoplasma, the actual contamination rate may be higher. European contamination rates are higher and that of other countries are higher still (up to 80% of Japanese cell cultures).
About 1% of published Gene Expression Omnibus data may have been compromised. Several antibiotic based formulation of anti-mycoplasma reagents have been developed over the years.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
that lack a cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
. Without a cell wall, they are unaffected by many common antibiotics such as penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
or other beta-lactam
Beta-lactam
A β-lactam ring, is a four-membered lactam. It is named as such, because the nitrogen atom is attached to the β-carbon relative to the carbonyl...
antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
ic in humans, including M. pneumoniae
Mycoplasma pneumoniae
Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes.It causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia, and is related to cold agglutinin disease.-Cell wall/Treatment:...
, which is an important cause of atypical pneumonia
Atypical pneumonia
Atypical pneumonia aka "walking pneumonia" is a pneumonia not caused by one of the more traditional pathogens, and with a clinical presentation inconsistent with typical pneumonia. It can be caused by a variety of microorganisms...
and other respiratory disorders, and M. genitalium
Mycoplasma genitalium
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 recently-discovered endosymbiont...
, which is believed to be involved in pelvic inflammatory diseases. Mycoplasma is the smallest known cell and is about 0.1 μ micron in diameter.
Origin of the name
The name Mycoplasma, from the Greek mykes (fungus) and plasma (formed), was first used by A. B. Frank in 1889. He thought it was a fungus, due to fungus-like characteristics.An older name for Mycoplasma was Pleuropneumonia-Like Organisms (PPLO), referring to organisms similar to the causative agent of contagious bovine pleuropneumonia
Contagious bovine pleuropneumonia
Contagious bovine pleuropneumonia , is a contagious bacterial disease that afflicts the lungs of cattle, buffalo, zebu, and yaks....
(CBPP). It was later found that the fungus-like growth pattern of M. mycoides is unique to that species.
Characteristics
There are over 100 recognized species of the genus Mycoplasma, one of several genera within the bacterial classClass (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Mollicutes
Mollicutes
The Mollicutes are a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin mollis , and cutis . They are parasites of various animals and plants, living on or in the host's cells. Individuals are very small, typically only 0.2–0.3 μm in size...
. Mollicutes are parasites or commensals of humans, other animals (including insects), and plants; the genus Mycoplasma is by definition restricted to vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
hosts. Cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...
is required for the growth of species of the genus Mycoplasma as well as certain other genera of mollicutes. Their optimum growth temperature is often the temperature of their host if warmbodied (e. g. 37° C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
in humans) or ambient temperature if the host is unable to regulate its own internal temperature. Analysis of 16S ribosomal RNA
Ribosomal RNA
Ribosomal ribonucleic acid is the RNA component of the ribosome, the enzyme that is the site of protein synthesis in all living cells. Ribosomal RNA provides a mechanism for decoding mRNA into amino acids and interacts with tRNAs during translation by providing peptidyl transferase activity...
sequences as well as gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
content strongly suggest that the mollicutes, including the mycoplasmas, are closely related to either the Lactobacillus
Lactobacillus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...
or the Clostridium
Clostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...
branch of the phylogenetic tree (Firmicutes
Firmicutes
The Firmicutes are a phylum of bacteria, most of which have Gram-positive cell wall structure. A few, however, such as Megasphaera, Pectinatus, Selenomonas and Zymophilus, have a porous pseudo-outer-membrane that causes them to stain Gram-negative...
sensu stricto).
Cell morphology
The bacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
of the genus Mycoplasma (trivial name: mycoplasmas) and their close relatives are characterized by lack of a cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
. Despite this, the cells often present a certain shape, with a characteristic small size, with typically about 10% of the volume of an Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
cell. These cell shapes presumably contribute to the ability of mycoplasmas to thrive in their respective environments. Most are pseudococcoidal, but there are notable exceptions. Species of the M. fastidiosum cluster are rod-shaped. Species of the M. pneumoniae cluster, including M. pneumoniae
Mycoplasma pneumoniae
Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes.It causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia, and is related to cold agglutinin disease.-Cell wall/Treatment:...
, possess a polar extension protruding from the pseudococcoidal cell body. This tip structure, designated an attachment organelle or terminal organelle, is essential for adherence to host cells and for movement along solid surfaces (gliding motility), and is implicated in normal cell division. M. pneumoniae cells are pleomorphic, with an attachment organelle of regular dimensions at one pole and a trailing filament of variable length and uncertain function at the other end, whereas other species in the cluster typically lack the trailing filament. Other species like M. mobile and M. pulmonis have similar structures with similar functions.
Mycoplasmas are unusual among bacteria in that most require sterols for the stability of their cytoplasmic membrane. Sterols are acquired from the environment, usually as cholesterol from the animal host. Mycoplasmas generally possess a relatively small genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
of 0.58-1.38 megabases, which results in drastically reduced biosynthetic capabilities and explains their dependence on a host. Additionally they use an alternate genetic code
Genetic code
The genetic code is the set of rules by which information encoded in genetic material is translated into proteins by living cells....
where the codon UGA is encoding for the amino acid tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
instead of the usual opal stop codon
Stop codon
In the genetic code, a stop codon is a nucleotide triplet within messenger RNA that signals a termination of translation. Proteins are based on polypeptides, which are unique sequences of amino acids. Most codons in messenger RNA correspond to the addition of an amino acid to a growing polypeptide...
. They have a low GC-content
GC-content
In molecular biology and genetics, GC-content is the percentage of nitrogenous bases on a DNA molecule that are either guanine or cytosine . This may refer to a specific fragment of DNA or RNA, or that of the whole genome...
(23-40 mol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
%).
First isolation
In 1898 Nocard and Roux reported the cultivation of the causative agent of CBPP, which was at that time a grave and widespread disease in cattle herds. The disease is caused by M. mycoidesMycoplasma mycoides
Mycoplasma mycoides is a bacterial species of the genus Mycoplasma in the class Mollicutes.This microorganism is a parasite that lives in ruminants , causing lung disease....
subsp. mycoides SC (small-colony type), and the work of Nocard and Roux represented the first isolation of a mycoplasma species. Cultivation was, and still is difficult because of the complex growth requirements.
These researchers succeeded by inoculating a semi-permeable pouch of sterile medium with pulmonary fluid from an infected animal and depositing this pouch intraperitoneally into a live rabbit. After fifteen to twenty days, the fluid inside of the recovered pouch was opaque, indicating the growth of a microorganism. Opacity of the fluid was not seen in the control. This turbid broth could then be used to inoculate a second and third round and subsequently introduced into a healthy animal, causing disease. However, this did not work if the material was heated, indicating a biological agent at work. Uninoculated media in the pouch, after removal from the rabbit, could be used to grow the organism in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
, demonstrating the possibility of cell-free cultivation and ruling out viral causes, although this was not fully appreciated at the time .
Small genome
Recent advances in molecular biologyMolecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
and genomics
Genomics
Genomics is a discipline in genetics concerning the study of the genomes of organisms. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale genetic mapping efforts. The field also includes studies of intragenomic phenomena such as heterosis,...
have brought the genetically simple mycoplasmas, particularly M. pneumoniae and its close relative M. genitalium
Mycoplasma genitalium
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 recently-discovered endosymbiont...
, to a larger audience. The second published complete bacterial genome sequence was that of M. genitalium, which has one of the smallest genomes of free-living organisms. The M. pneumoniae genome sequence was published soon afterwards and was the first genome sequence determined by primer walking
Primer walking
Primer walking is a sequencing method of choice for sequencing DNA fragments between 1.3 and 7 kilobases. Such fragments are too long to be sequenced in a single sequence read using the chain termination method. This method works by dividing the long sequence into several consecutive short ones...
of a cosmid
Cosmid
A cosmid, first described by Collins and Hohn in 1978, is a type of hybrid plasmid that contains cos sequences, DNA sequences originally from the Lambda phage. Cosmids can be used to build genomic libraries....
library instead of the whole-genome shotgun method. Mycoplasma genomics and proteomics
Proteomics
Proteomics is the large-scale study of proteins, particularly their structures and functions. Proteins are vital parts of living organisms, as they are the main components of the physiological metabolic pathways of cells. The term "proteomics" was first coined in 1997 to make an analogy with...
continue in efforts to understand the
so-called minimal cell
Mycoplasma laboratorium
Mycoplasma laboratorium is a planned partially synthetic species of bacterium derived from the genome of Mycoplasma genitalium. This effort in synthetic biology is being undertaken at the J. Craig Venter Institute by a team of approximately 20 scientists headed by Nobel laureate Hamilton Smith, and...
, catalog the entire protein content of a cell, and generally continue to take advantage of the small genome of these organisms to understand broad biological concepts.
Taxonomy
The medical and agricultural importance of members of the genus Mycoplasma and related genera has led to the extensive cataloging of many of these organisms by culture, serologySerology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...
, and small subunit rRNA
Ribosomal RNA
Ribosomal ribonucleic acid is the RNA component of the ribosome, the enzyme that is the site of protein synthesis in all living cells. Ribosomal RNA provides a mechanism for decoding mRNA into amino acids and interacts with tRNAs during translation by providing peptidyl transferase activity...
gene and whole genome sequencing. A recent focus in the sub-discipline of molecular phylogenetics has both clarified and confused certain aspects of the organization of the class Mollicutes.
Originally the trivial name "mycoplasmas" has commonly denoted all members of the class Mollicutes
Mollicutes
The Mollicutes are a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin mollis , and cutis . They are parasites of various animals and plants, living on or in the host's cells. Individuals are very small, typically only 0.2–0.3 μm in size...
. The name "Mollicutes" is derived from the Latin mollis (soft) and cutes (skin), and all of these bacteria do lack a cell wall and the genetic capability to synthesize peptidoglycan
Peptidoglycan
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid...
. Now Mycoplasma is a genus in Mollicutes. Despite the lack of a cell wall, many taxonomists have classified Mycoplasma and relatives in the phylum Firmicutes
Firmicutes
The Firmicutes are a phylum of bacteria, most of which have Gram-positive cell wall structure. A few, however, such as Megasphaera, Pectinatus, Selenomonas and Zymophilus, have a porous pseudo-outer-membrane that causes them to stain Gram-negative...
, consisting of low G+C Gram-positive bacteria such as Clostridium
Clostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...
, Lactobacillus
Lactobacillus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...
, and Streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
based on 16S rRNA gene analysis. The order Mycoplasmatales contains a single family, Mycoplasmataceae
Mycoplasmataceae
The Mycoplasmataceae is a family of bacteria in the order Mycoplasmatales. This family comprises the species Mycoplasma and Ureaplasma.In 1967 the Order Mycoplasmatales was incorporated into the class Mollicutes....
, comprising two genera: Mycoplasma and Ureaplasma
Ureaplasma
Ureaplasma is a genus of bacteria belonging to the family Mycoplasmataceae. As the name imples, ureaplasma is urease positive.It includes the species:* Ureaplasma canigenitalium* Ureaplasma cati* Ureaplasma diversum...
.
Historically, the description of a bacterium lacking a cell wall was sufficient to classify it to the genus Mycoplasma and as such it is the oldest and largest genus of the class with about half of the class' species (107 validly described), each usually limited to a specific host and with many hosts harboring more than one species, some pathogenic and some commensal. In later studies, many of these species were found to be phylogenetically distributed among at least three separate orders.
A limiting criterion for inclusion within the genus Mycoplasma is that the organism have a vertebrate host. In fact, the type species, M. mycoides
Mycoplasma mycoides
Mycoplasma mycoides is a bacterial species of the genus Mycoplasma in the class Mollicutes.This microorganism is a parasite that lives in ruminants , causing lung disease....
, along with other significant mycoplasma species like M. capricolum, is evolutionarily more closely related to the genus Spiroplasma
Spiroplasma
Spiroplasma is a genus of Mollicutes, a group of small bacteria without cell walls. Spiroplasma shares the simple metabolism, parasitic lifestyle, fried-egg colony morphology and small genome of other Mollicutes, but has a distinctive helical morphology, unlike Mycoplasma. It has a spiral shape...
in the order Entomoplasmatales than to the other members of the Mycoplasma genus. This and other discrepancies will likely remain unresolved because of the extreme confusion that change could engender among the medical and agricultural communities.
The remaining species in the genus Mycoplasma are divided into three non-taxonomic groups, hominis, pneumoniae and fermentans, based on 16S rRNA gene sequences.
The hominis group contains the phylogenetic clusters of M. bovis, M. pulmonis, and M. hominis
Mycoplasma hominis
Mycoplasma hominis is a strain of bacteria present in the vagina. It may or may not belong to the normal vaginal flora. It is also believed to be a cause of pelvic inflammatory disease. If so, it would be only one of many known causes....
, among others. M. hyopneumoniae
Mycoplasma hyopneumoniae
-Introduction:Mycoplasma hyopneumoniae is a species of bacteria known to cause the disease Porcine Enzootic Pneumonia, a highly contagious and chronic disease affecting pigs . As with other mollicutes, M...
is a primary bacterial agent of the porcine respiratory disease complex.
The pneumoniae group contains the clusters of M. muris, M. fastidiosum, U. urealyticum
Ureaplasma urealyticum
Ureaplasma urealyticum is a bacterium belonging to the family Mycoplasmataceae. Its type strain is T960.-Clinical significance:U. urealyticum is part of the normal genital flora of both men and women...
, the currently unculturable haemotrophic mollicutes, informally referred to as haemoplasmas (recently transferred from the genera Haemobartonella and Eperythrozoon), and the M. pneumoniae cluster. This cluster contains the species (and the usual or likely host) M. alvi (bovine), M. amphoriforme (human), M. gallisepticum
Mycoplasma gallisepticum
Mycoplasma gallisepticum is a bacterium belonging to the class Mollicutes and the family Mycoplasmataceae. It is the causative agent of chronic respiratory disease in chickens and infectious sinusitis in turkeys, chickens, game birds, pigeons, and passerine birds of all ages.-Transmission:MG is...
(avian), M. genitalium
Mycoplasma genitalium
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 recently-discovered endosymbiont...
(human), M. imitans (avian), M. pirum (uncertain/human), M. testudinis (tortoises), and M. pneumoniae
Mycoplasma pneumoniae
Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes.It causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia, and is related to cold agglutinin disease.-Cell wall/Treatment:...
(human). Most if not all of these species share some otherwise unique characteristics including an attachment organelle, homologs of the M. pneumoniae cytadherence-accessory proteins, and specialized modifications of the cell division apparatus.
A study of 143 genes in 15 species of Mycoplasma suggests that the genus can be grouped into four clades: the M. hyopneumoniae group, the M. mycoides group, the M. pneumoniae group and a Bacillus-Phytoplasma group. The M. hyopneumoniae group is more closely related to the M. pneumoniae group than the M. mycoides group.
Laboratory contaminant
Mycoplasma species are often found in research laboratories as contaminants in cell cultureCell culture
Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
. Mycoplasmal cell culture contamination occurs due to contamination from individuals or contaminated cell culture medium ingredients. Mycoplasma cells are physically small – less than 1 µm – and they are therefore difficult to detect with a conventional microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
. Mycoplasmas may induce cellular changes, including chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
aberrations, changes in metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
and cell growth. Severe Mycoplasma infections may destroy a cell line. Detection techniques include DNA Probe, enzyme immunoassays
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
, PCR
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
, plating on sensitive agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
and staining with a DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
stain including DAPI
DAPI
DAPI or 4',6-diamidino-2-phenylindole is a fluorescent stain that binds strongly to A-T rich regions in DNA. It is used extensively in fluorescence microscopy...
or Hoechst
Hoechst stain
Hoechst stains are part of a family of blue fluorescent dyes used to stain DNA. These Bis-benzimides were originally developed by the Hoechst AG, which numbered all their compounds so that the dye Hoechst 33342 is the 33342nd compound made by the company. There are three related Hoechst stains:...
.
It has been estimated that at least 11 to 15% of U.S. laboratory cells cultures are contaminated with mycoplasma.
A Corning study showed that half of U.S. scientists did not test for mycoplasma contamination in their cell cultures. The study also stated that, in Czechoslovakia, 100% of cell cultures that were not routinely tested were contaminated while only 2% of those routinely tested were contaminated. (study page 6) Since the U.S. contamination rate was based on a study of companies that routinely checked for mycoplasma, the actual contamination rate may be higher. European contamination rates are higher and that of other countries are higher still (up to 80% of Japanese cell cultures).
About 1% of published Gene Expression Omnibus data may have been compromised. Several antibiotic based formulation of anti-mycoplasma reagents have been developed over the years.
Synthetic mycoplasma genome
A chemically synthesized genome of a mycoplasmal cell based entirely on synthetic DNA which can self-replicate has been created.External links
- Bionique Testing Laboratories, Inc. Mycoplasma resources, technical articles and testing kits.
- Compare the size of these small bacteria to the sizes of other cells and viruses.
- MedPix(r)Images Mycoplasma Pneumonia
- Ureaplasma Infection: eMedicine Infectious Diseases
- Antibiotics formulation for eradication of mycoplasma in cell culture media.
- Mycoplasma elimination and prevention in cell culture