What is the Thermoproteus habitat?

What are the characteristics of Thermoprotei?

The Thermoprotei (literally heat-loving) are a group of anaerobic, hyperthermophilic archaea. They do not possess motility, and are surrounded by an extracellular polysaccharide sheath. Their cell walls are composed of polysulfide-like polymers, some of which have been shown to be covalently linked to the membrane.

Characteristics. Cell shape: The Thermoprotei are nonmotile, but are covered by an extracellular polysaccharide sheath. Nucleus: Thermoprotei do not possess a true nucleus. However, they contain a large nucleoid that encases the entire genome.

Photosynthetic system: Most of the Thermoprotei are photosynthetic, and some are able to synthesize their own cofactors in situ. Metabolism: The Thermoprotei do not possess a flagellum, and therefore are unable to move themselves across surfaces. However, they are able to swim on surfaces via two types of motility systems. One of these systems allows them to move in two dimensions, and is powered by an extracellular "gliding" polymer. The second system of motility requires a continuous supply of energy from substrate oxidation. This system allows them to move in three dimensions, and is powered by a specialized ATPase (PBP) that produces high-energy phosphate bonds during substrate-assisted transport.

Reproduction: Thermoprotei reproduce by binary fission, and form aggregates at mid-cell. Growth conditions: Thermoprotei are strict anaerobes. They can grow under extreme conditions of high temperature, pressure, and low pH, but are not able to survive without a substrate.

Chemotaxis: Thermoprotei are chemotactic toward sulfide, and the concentration gradient of sulfide can direct the migration of cells. Respiration: Thermoprotei oxidize sulfide as their primary respiratory substrate. Most Thermoprotei oxidize hydrogen sulfide, and couple this reaction to proton translocation across the plasma membrane. They also produce formate, which is used by a formate transporter.

What is a Thermoprotei?

The Thermoprotei are the second-largest group of the Thermophilic Anaerobic Bacteria (TBA) that are adapted to survive in extreme thermal conditions. They are strictly anaerobic and can tolerate high temperatures, being capable of growing at 70C and below. As the name implies, they thrive in hot springs, and even in the absence of oxygen.

However, they prefer to live in an environment where the temperature is between 85C and 105C and with little or no presence of oxygen. These environments are generally limited to volcanic systems, geothermal vents and the deep ocean. The main difference between the Thermoprotei and other groups of TBA is that they are metabolically active in a non-oxidative environment.

In recent years, a number of them have been found living in the guts of animals. Most of the information available on them is derived from studies performed on the genus Thermodesulfatator. However, there are other Thermoprotei living in the guts of other animals, including humans.

Some species are pathogenic, while others have an essential role in the metabolism of other species. Although it is not possible to carry out research on these microorganisms as they do not grow in laboratory conditions, scientists have been able to gain valuable information on their metabolism.

Structure. The Thermoprotei are Gram-negative and chemo-organotrophs, which means that they use organic compounds as energy sources, but do not need oxygen to live. They are not motile, having a cytoplasmic membrane containing phospholipids, an outer membrane, and an inner one. The latter is responsible for all the metabolic processes, with the exception of respiration.

There are two major structures inside the cells of these microorganisms: the plasma membrane and the inner membrane. The plasma membrane is the first barrier to protect the organism against toxins and other harmful agents. The inner membrane is in charge of transferring metabolites between the inside and the outside of the cell, as well as providing the cell with energy.

Cell structure. Image taken from Biology. One of the most outstanding characteristics of the Thermoprotei is their ability tolerate temperatures above 100C.