desiccation tolerance

Examples of desiccation tolerance in the following topics:

• Plant Adaptations to Life on Land

  • Desiccation, or drying out, is a constant danger for organisms exposed to air.
  • As such, both gametes and zygotes must be protected from desiccation.
  • One of these strategies is called desiccation tolerance.
  • Later, plants moved away from moist or aquatic environments and developed resistance to desiccation, rather than tolerance.
  • The vulnerable embryo must be sheltered from desiccation and other environmental hazards.

• Bryophytes

  • They constitute the major flora of inhospitable environments like the tundra where their small size and tolerance to desiccation offer distinct advantages.

• Desiccation

  • Desiccation is the state of extreme dryness, or the process of extreme drying and can be used to control microbial growth.
  • Desiccation is the state of extreme dryness, or the process of extreme drying.
  • In biology and ecology, desiccation refers to the drying out of a living organism.
  • After the addition of water, the bacteria will start growing again, so desiccation does not provide complete sterilization.
  • Some bacteria, such as Deinococcus radiodurans and Mycobacterium, are extremely resistant to damage from prolonged desiccation while others, such as Neisseria gonorrhoeae, can survive only short periods of desiccation.

• Non-Spore-Forming Firmicutes

  • Many Firmicutes produce endospores, which are resistant to desiccation and can survive extreme conditions.
  • These comprise a class of Firmicutes and are Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics.
  • The lactic acid bacteria (LAB) are rod-shaped bacilli or cocci , characterized by an increased tolerance to a lower pH range.
  • A Gram-positive, catalase-positive bacterium which is rod-shaped, and has the ability to form a tough, protective endospore, allowing the organism to tolerate extreme environmental conditions.

• Clonal Selection and Tolerance

  • The concept of central tolerance was proposed in 1959 as part of a general theory of immunity and tolerance.
  • It was hypothesized that it is the age of the lymphocyte that defines whether an antigen that is encountered will induce tolerance, with immature lymphocytes being tolerance sensitive.
  • Central tolerance is distinct from periphery tolerance in that it occurs while cells are still present in the primary lymphoid organs (thymus and bone-marrow), prior to export into the periphery.
  • Peripheral tolerance is generated after the cells reach the periphery.
  • Regulatory T cells can be considered both central tolerance and peripheral tolerance mechanisms, as they can be generated from self (or foreign)-reactive T cells in the thymus during T cell differentiation.

• Deinococcus and Thermus

  • It is extremely resistant to ionizing radiation, ultraviolet light, desiccation, and oxidizing and electrophilic agents.
  • A genus of thermophilic bacteria that can tolerate high temperatures, it is one of several bacteria belonging to the Deinococcus-Thermus group and includes the following three species: T. aquaticus, T. antranikianii, and T. igniterrae.

• Biofilms, Persisters, and Antibiotic Tolerance

  • Biofilms and persisters are bacterial communities responsible for chronic diseases and antibiotic tolerance.
  • Persisters are multidrug tolerant cells present in all bacterial populations.
  • Persisters are not mutants, but rather phenotypic variants of the wild-type that upon inoculation produce a culture with similar levels of tolerance.
  • Biofilms and persisters are the cause of multidrug tolerance.
  • Explain the role of biofilms and persisters in multidrug tolerance, distinguishing this from multidrug resistance

• The Evolution of Seed Plants and Adaptations for Land

  • Several layers of hardened tissue prevent desiccation, freeing reproduction from the need for a constant supply of water.
  • Furthermore, seeds remain in a state of dormancy induced by desiccation and the hormone abscisic acid until conditions for growth become favorable.
  • The whole structure is protected from desiccation and can reach the female organs without dependence on water.

• Glycocalyx

  • Capsules also contain water which protects bacteria against desiccation.
  • The function of the slime layer is to protect the bacteria cells from environmental dangers such as antibiotics and desiccation.

• Regulating Immune Tolerance

  • Immune tolerance of self and harmless antigens occurs by deleting B and T cells that recognize those antigens, often near mucosal surfaces.
  • The acquired ability to prevent an unnecessary or harmful immune response to a detected foreign substance known not to cause disease or to self-antigens is described as immune tolerance.
  • The primary mechanism for developing immune tolerance to self-antigens occurs during the selection for weakly, self-binding cells during T and B lymphocyte maturation.
  • Immune tolerance is especially well developed in the mucosa of the upper digestive system because of the tremendous number of foreign substances (such as food proteins) that APCs of the oral cavity, pharynx, and gastrointestinal mucosa encounter.
  • Immune tolerance is brought about by specialized APCs in the liver, lymph nodes, small intestine, and lung that present harmless antigens to a diverse population of regulatory T (Treg) cells: specialized lymphocytes that suppress local inflammation and inhibit the secretion of stimulatory immune factors.