Thermoplasma acidophilum

From MicrobeWiki, the student-edited microbiology resource

A Microbial Biorealm page on the genus Thermoplasma acidophilum

Classification

Higher order taxa

Cellular organisms;Archaea; Euryarchaeota; Thermoplasmata; Thermoplasmatales; Thermoplasmataceae; Thermoplasma acidophilum

Genus

Thermoplasma


NCBI: Taxonomy

Description and significance

“Thermoplasma acidophilum is a thermophilic heterotrophic prokaryote growing at 55-60°C and pH 0.5-4, It is among the most acidophilic organisms known.” It is found and first isolated from self-heating coal refuse piles and solfatara fields.

“Microbial physiologists and structural biologists have long been fascinated by the ability of this microorganism to grow at high temperatures and low pH without the structural protection of a conventional cell wall”, “our interest in protein folding and degradation led us to seek a more complete representation of the proteins involved in these pathways by determining the genome sequence of this organism.”

Genome structure

Thermoplasma Acidophilum’s genome contain special gene that allow this organism to survive in an environment similar in temperature and acidity to hot vinegar.

The genome is a single circular chromosome and was sequenced using a new strategy called "shotgun sequencing".It is one of the smallest microbial genomes ever sequenced. “The genome of the organism consists of a single circular chromosome of 1.56 Mbp, containing 1509 ORFs. These identify Thermoplasma as a typical euryarchaeon with a substantial complement of bacterial-related genes. However, massive lateral gene transfer appears to have occurred between Thermoplasma and Sulfolobus solfataricus, a phylogenetically distant crenarchaeon inhabiting the same environment.”

Cell structure and metabolism

Species of the genus Thermoplasma lack rigid cell wall, but are only delimited by a plasma membrane, it is “devoid of protective outer shells (S-layer, cell wall), yet maintains a near-neutral cytosolic pH.” However, Thermoplasma is flagellated and motile2, yet lacks recognizable chemotaxis proteins. In Thermoplasma, “glucose degradation proceeds by a non-phosphorylated variant of the Entner–Doudoroff pathway, in which the first step is catalysed by glucose dehydrogenase. The acetyl-CoA produced in this pathway enters the oxidative tricarboxylic acid (TCA) cycle.” (the presence of enzyme require for this pathway had already been experimentally confirmed), the presence of glycolysis/gluconeogenesis has not yet been confirmed due to the absence of phosphofructokinase and fructose in this organism. “Thermoplasma is also able to gain energy anaerobically by sulphur respiration. “It has adapted to scavenging nutrients from the decomposition of organisms killed by the extreme acidity and requires yeast, bacterial or meat extract when grown in culture.”

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

1) “Large chunks of DNA which have been borrowed from other species of microbe and incorporated into the chromosome of acidophilum. The genes are believed to come from microbes and bacteria that share the same environmental niches, like the soil near hydrothermal sites.”

2) Ubiquitin found in the archaebacterium Thermoplasma acidophilum strongly suggests that ATP-ubiquitin-dependent proteolysis is a cellular function that developed early in evolution.

3) Thermoplasma acidophilum has no cell wall, and so its irregular shape implies the presence of a cytoskeleton.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Rachel Larsen and Kit Pogliano