Spiroplasma
Encyclopedia
Spiroplasma is a genus of Mollicutes
, a group of small bacteria
without cell wall
s. 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 and moves in a corkscrew motion. Most spiroplasmas are found either in the gut or hemolymph
of insects, or in the phloem
of plants. Spiroplasmas are fastidious
organisms, which require a rich culture medium. Typically they grow well at 30°C, but not at 37°C. A few species, notably Spiroplasma mirum, grow well at 37°C (human body temperature), and cause cataract
s and neurological damage in suckling mice. The best studied species of spiroplasmas are Spiroplasma citri, the causative agent of Citrus Stuborn Disease, and Spiroplasma kunkelii, the causative agent of Corn Stunt Disease.
There is some disputed evidence for the role of spiroplasmas in the etiology
of Transmissible Spongiform Encephalopathies
(TSEs), due primarily to the work of Dr. Bastian, summarized below. Other researchers, such as Leach et al. (1983) have failed to replicate this work, while the prion
model for TSEs has gained very wide acceptance. The most recent work of Alexeeva et al. (2006) appears to refute the role of spiroplasmas in the best small animal scrapie
model (hamsters). Bastian et al. (2007) have responded to this challenge with the isolation of a spiroplasma species from scrapie-infected tissue, grown it in cell-free culture, and demonstrated its infectivity in ruminants.
According to Frank O. Bastian, MD:
In addition, a Spiroplasma species had been shown to kill males of the Plain Tiger butterfly
on infection, leading to interesting consequences for population genetics
and consequently speciation
similar to the effects caused by some strains of Wolbachia
(Jiggins et al. 2000).
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...
, a group of small 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...
without 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...
s. Spiroplasma shares the simple 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...
, parasitic lifestyle, fried-egg colony morphology and small genome of other Mollicutes, but has a distinctive helical morphology, unlike Mycoplasma
Mycoplasma
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 pathogenic in humans,...
. It has a spiral shape and moves in a corkscrew motion. Most spiroplasmas are found either in the gut or hemolymph
Hemolymph
Hemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods and is analogous to the fluids and cells making up both blood and interstitial fluid in vertebrates such as birds and mammals...
of insects, or in the phloem
Phloem
In vascular plants, phloem is the living tissue that carries organic nutrients , in particular, glucose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word "bark"...
of plants. Spiroplasmas are fastidious
Growth medium
A growth medium or culture medium is a liquid or gel designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.There are different types of media for growing different types of cells....
organisms, which require a rich culture medium. Typically they grow well at 30°C, but not at 37°C. A few species, notably Spiroplasma mirum, grow well at 37°C (human body temperature), and cause cataract
Cataract
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
s and neurological damage in suckling mice. The best studied species of spiroplasmas are Spiroplasma citri, the causative agent of Citrus Stuborn Disease, and Spiroplasma kunkelii, the causative agent of Corn Stunt Disease.
There is some disputed evidence for the role of spiroplasmas in the etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
of Transmissible Spongiform Encephalopathies
Transmissible spongiform encephalopathy
Transmissible spongiform encephalopathies , also known as prion diseases, are a group of progressive conditions that affect the brain and nervous system of many animals, including humans. According to the most widespread hypothesis they are transmitted by prions, though some other data suggest an...
(TSEs), due primarily to the work of Dr. Bastian, summarized below. Other researchers, such as Leach et al. (1983) have failed to replicate this work, while the prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...
model for TSEs has gained very wide acceptance. The most recent work of Alexeeva et al. (2006) appears to refute the role of spiroplasmas in the best small animal scrapie
Scrapie
Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies , which are related to bovine spongiform encephalopathy and chronic wasting disease of deer. Like other spongiform encephalopathies, scrapie...
model (hamsters). Bastian et al. (2007) have responded to this challenge with the isolation of a spiroplasma species from scrapie-infected tissue, grown it in cell-free culture, and demonstrated its infectivity in ruminants.
According to Frank O. Bastian, MD:
"spiroplasmas contain internal fibrillar proteins, that have morphological and immunological similarities to scrapie- and CJD-related fibrillar proteins. This comparison is noteworthy since mycoplasmologists consider these fibril proteins unique to this prokaryote.
In vivoIn vivoIn vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
and in vitroIn vitroIn 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...
experimental Spiroplasma infections produce cytopathic effectCytopathic effectCytopathic effect or cytopathogenic effect refers to degenerative changes in cells, especially in tissue culture, and may be associated with the multiplication of certain viruses....
s similar to those of the scrapie agent. Experimental Spiroplasma brain infection in the suckling rat is characterized by vacuolar encephalopathyEncephalopathyEncephalopathy means disorder or disease of the brain. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of global brain dysfunction; this syndrome can be caused by many different illnesses.-Terminology:...
with localization of the microbe to gray matter.
[...] Spiralins are chemically bound to Spiroplasma-associated fibrils (SpFs) and are separated with difficulty.' SpFs are unique internal fibrils of spiroplasmas with a molecular weight of 55 kDa. Recently, SpFs have been shown to bear close morphological resemblance to scrapie-associated fibrils (SAFS), ' and show cross-reactivity using SAF antibody."
In addition, a Spiroplasma species had been shown to kill males of the Plain Tiger butterfly
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
on infection, leading to interesting consequences for population genetics
Population genetics
Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...
and consequently speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
similar to the effects caused by some strains of Wolbachia
Wolbachia
Wolbachia is a genus of bacteria which infects arthropod species, including a high proportion of insects , as well as some nematodes. It is one of the world's most common parasitic microbes and is possibly the most common reproductive parasite in the biosphere...
(Jiggins et al. 2000).