Epulopiscium fishelsoni

Epulopiscium fischelsoni
Scientific classification
Kingdom:Bacteria
Phylum:Firmicutes
Class:Clostridia
Order:Clostridiales
Genus:Epulopiscium
Species:E. fishelsoni
Binomial name
Epulopiscium fishelsoni
Schulz et al., 1999


Epulopiscium fishelsoni ("guest at a fish's banquet") is a gram-positive bacterium that has a symbiotic relationship with the surgeonfish. It is most well-known for its large size, ranging from 200-700 μm in length, and about 80 μm in diameter. Until the discovery of Thiomargarita namibiensis in 1999, it was the largest bacteria known.

Discovery

Epulopiscium was first discovered in 1985 by the Israeli scientist Lev Fishelson from Tel Aviv University, inside the intestines of a brown surgeonfish. It was initially classified as a protist on the basis of its large size, until rRNA analysis by Pace, et al in 1993 confirmed that it was a member of the bacteria. (Epulopiscium can reach up to three times the length of the average paramecium.)

Physiology

The bacteria exhibit many unusual characteristics, mostly due to the adaptations necessary for their large size. Epulopiscium is extremely polyploid, with bacterial chromosomes representing as much as 1,000 copies of the genome throughout the cell at any given time. Since bacteria rely on diffusion rather than cytoskeletal transport as in eukaryotes, this over-expression may be necessary for proteins to disperse throughout the cell. This polyploidy is also associated with a very high efflux rate, due to the over-expression of genes for export pumps.

Epulopiscium has a unique anatomy which is designed to overcome the size limitations inherent in cell volume. Its cell wall contains many folds in order to increase surface area, and it possesses an unusual "cortex" containing tubules, vesicles, and other structures which are usually found in eukaryotes. It may be the case that these structures are involved in intracellular transport, which would provide a unique example of convergent evolution on the cellular level.

While these adaptions allow the bacteria to break the theoretical upper limit for size, the underlying evolutionary reasons for the bacteria to grow to this size in the first place remain speculative. One possible reason could be the ability to avoid predation by protists.

Reproduction

Perhaps the most intriguing aspect of the bacteria is its unusual, almost viviparous reproductive cycle. Unlike most bacteria, which undergo binary fission, Epulopiscium reproduces exclusively through an unusual form of sporulation in which anywhere from one to twelve daughter cells are grown inside of the parent cell, until the cell eventually lyses and the new bacteria burst through the cell wall. Although sporulation is common among other bacteria (such as Bacillus subtilis), it is a desperation measure brought about by overcrowding or starvation, rather than a standard form of reproduction. Also, the daughter cells in standard sporulation are usually dormant, while new Epulopiscium cells are active.

This form of reproduction has been observed in other large gut symbionts (Metabacterium polyspora), which are phylogenetically related to Epulopiscium. Since sporulation affords bacteria much more protection from the outside environment than binary fission, it is thought that the evolution of this unusual life cycle may be in order to allow transfer of the bacteria from one host to another, and also provide protection during reproduction from the harsh environment of the digestive system.

Symbiosis

Different strains of Epulopiscium have been isolated in most surgeonfish species around the world, and scientists have been unable to culture Epulopiscium outside of its natural habitat, meaning that the relationship between the two is probably mutually beneficial and symbiotic.

The daily life cycle of Epulopiscium exhibits a correlation with the daily activities of the surgeonfish. During the day, when the surgeonfish feed on algae, the bacteria's compact, spherical nucleoids migrate to the poles of the cell and begin to elongate. As the day goes on, the average length of the cells increase, until the nucleoids make up a large percentage of the parent cell volume, and the sporulation process begins in the late afternoons and evenings, when these nucleoids reach a maximum of approximately 50 - 75% of the length of the parent cells. The pH of the surgeonfish's gut also shows a correlation with the daily life cycle of the bacteria, showing that they suppress it during the day.

Although the exact biochemical nature of the symbiosis remains unclear, it is safe to assume that the bacteria assist the fish in breaking down algal nutrients. Many bacteria of the genus Clostridia are gut symbionts in a variety of other species, including humans, usually involved in breaking down complex carbohydrates.

External links

Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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Bacteria

Phyla

Actinobacteria
Aquificae
Chlamydiae
Bacteroidetes/Chlorobi
Chloroflexi
Chrysiogenetes
Cyanobacteria
Deferribacteres
Deinococcus-Thermus
Dictyoglomi
Fibrobacteres/Acidobacteria
Firmicutes
Fusobacteria
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Firmicutes

Classes

Bacilli
Clostridia
Mollicutes
The Firmicutes are a division of bacteria, most of which have Gram-positive cell wall structure.
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Clostridia

Orders

Clostridiales
   Acidaminococcaceae
   Clostridiaceae
   Eubacteriaceae
   Heliobacteriaceae
   Lachnospiraceae
   Peptococcaceae
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Clostridia

Orders

Clostridiales
   Acidaminococcaceae
   Clostridiaceae
   Eubacteriaceae
   Heliobacteriaceae
   Lachnospiraceae
   Peptococcaceae
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binomial nomenclature is the formal system of naming species. The system is also called binominal nomenclature (particularly in zoological circles), binary nomenclature (particularly in botanical circles), or the binomial classification system.
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Gram-positive bacteria are those that retain a crystal violet dye during the Gram stain process.[1] Gram-positive bacteria appear blue or violet under a microscope, while Gram-negative bacteria appear red or pink.
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Bacteria

Phyla

Actinobacteria
Aquificae
Chlamydiae
Bacteroidetes/Chlorobi
Chloroflexi
Chrysiogenetes
Cyanobacteria
Deferribacteres
Deinococcus-Thermus
Dictyoglomi
Fibrobacteres/Acidobacteria
Firmicutes
Fusobacteria
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symbiosis (from the Greek: συμ, sym, "with"; and βίοσίς, biosis, "living") can be used to describe various degrees of close relationship between organisms of different species.
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Acanthuridae

Genera

Acanthurus
Ctenochaetus
Naso (unicornfishes)
Paracanthurus
Prionurus
Zebrasoma (tangs)
Acanthuridae
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1 micrometre =
SI units
010−6 m 010−3 mm
US customary / Imperial units
010−6 ft 010−6 in
A micrometre (American spelling: micrometer; symbol µm
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Thiomargarita

Species: T. namibiensis

Binomial name
Thiomargarita namibiensis
Schulz et al.
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20th century - 21st century
1950s  1960s  1970s  - 1980s -  1990s  2000s  2010s
1982 1983 1984 - 1985 - 1986 1987 1988

Year 1985 (MCMLXXXV) was a common year starting on Tuesday (link displays 1985 Gregorian calendar).
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Tel Aviv University (TAU, אוניברסיטת תל־אביב, את"א) is Israel's largest on-site university.
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In anatomy, the intestine is the segment of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine.
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Eukarya
Whittaker & Margulis, 1978

Kingdom: Protista*
Haeckel, 1866

Typical phyla
  • Chromalveolata
  • Chromista

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Paramecium
Müller, 1773

Species
Paramecium tetraurelia
Paramecium aurelia
Paramecium caudatum
Paramecium is a group of unicellular ciliate protozoa formerly known as slipper animalcules from their slipper shape.
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Polyploidy is the condition of some biological cells and organisms manifested by the presence of more than two homologous sets of chromosomes. Polyploid types are termed according to the number of chromosome sets in the nucleus: triploid (three sets; 3x),
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In biology the genome of an organism is its whole hereditary information and is encoded in the DNA (or, for some viruses, RNA). This includes both the genes and the non-coding sequences of the DNA.
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This article is about the physical mechanism of diffusion. For alternative meanings, see diffusion (disambiguation).


Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
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Active efflux is a mechanism responsible for extrusion of toxic substances and antibiotics outside the cell. Its importance lies in its contribution to bacterial antimicrobial resistance.
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A tubule is a very small tube or fistular structure.

In anatomy, a tubule is a minute tube lined with glandular epithelium.
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vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. If there is only one lipid bilayer, they are called unilamellar vesicles; otherwise they are called multilamellar.
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In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches[1].
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predation describes a biological interaction where a predator organism feeds on another living organism or organisms known as prey.[1] Predators may or may not kill their prey prior to feeding on them.
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viviparous animal is an animal employing vivipary: the embryo develops inside the body of the mother, as opposed to outside in an egg (ovipary). The mother then gives live birth.
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Binary fission is the form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. This process results in the reproduction of a living cell by division into two equal or near-equal parts.
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spore is a reproductive structure that is adapted for dispersion and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many plants, algae, fungi and some protozoans.
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subtilis

Binomial name
Bacillus subtilis
(Ehrenberg 1835)
Cohn 1872

Bacillus subtilis is a Gram-positive, catalase-positive bacterium commonly found in soil.
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