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Abiotic stress is the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performance or individual physiology of the organism in a significant way.
The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells. It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into many compartments.
Halotolerance is the adaptation of living organisms to conditions of high salinity. Halotolerant species tend to live in areas such as hypersaline lakes, coastal dunes, saline deserts, salt marshes, and inland salt seas and springs. Halophiles are organisms that live in highly saline environments, and require the salinity to survive, while halotolerant organisms can grow under saline conditions, but do not require elevated concentrations of salt for growth. Halophytes are salt-tolerant higher plants. Halotolerant microorganisms are of considerable biotechnological interest.
Cryptobiosis or anabiosis is a metabolic state in extremophilic organisms in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all measurable metabolic processes stop, preventing reproduction, development, and repair. When environmental conditions return to being hospitable, the organism will return to its metabolic state of life as it was prior to cryptobiosis.
A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists and in unicellular algae. It was previously known as pulsatile or pulsating vacuole.
In chemical biology, tonicity is a measure of the effective osmotic pressure gradient; the water potential of two solutions separated by a partially-permeable cell membrane. Tonicity depends on the relative concentration of selective membrane-impermeable solutes across a cell membrane which determine the direction and extent of osmotic flux. It is commonly used when describing the swelling-versus-shrinking response of cells immersed in an external solution.
Osmotic concentration, formerly known as osmolarity, is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution. The osmolarity of a solution is usually expressed as Osm/L, in the same way that the molarity of a solution is expressed as "M". Whereas molarity measures the number of moles of solute per unit volume of solution, osmolarity measures the number of osmoles of solute particles per unit volume of solution. This value allows the measurement of the osmotic pressure of a solution and the determination of how the solvent will diffuse across a semipermeable membrane (osmosis) separating two solutions of different osmotic concentration.
Ectoine is a natural compound found in several species of bacteria. It is a compatible solute which serves as a protective substance by acting as an osmolyte and thus helps organisms survive extreme osmotic stress. Furthermore it was shown to protect DNA against ionizing and ultraviolet radiation serving as a radical scavenger. Ectoine is found in high concentrations in halophilic microorganisms and confers resistance towards salt and temperature stress. Ectoine was first identified in the microorganism Ectothiorhodospira halochloris, but has since been found in a wide range of Gram-negative and Gram-positive bacteria. Other species of bacteria in which ectoine was found include:
Plasma osmolality measures the body's electrolyte–water balance. There are several methods for arriving at this quantity through measurement or calculation.
Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the short-finned molly, Poecilia sphenops, which can live in fresh water, brackish water, or salt water.
Osmotic shock or osmotic stress is physiologic dysfunction caused by a sudden change in the solute concentration around a cell, which causes a rapid change in the movement of water across its cell membrane. Under hypertonic conditions - conditions of high concentrations of either salts, substrates or any solute in the supernatant - water is drawn out of the cells through osmosis. This also inhibits the transport of substrates and cofactors into the cell thus “shocking” the cell. Alternatively, under hypotonic conditions - when concentrations of solutes are low - water enters the cell in large amounts, causing it to swell and either burst or undergo apoptosis.
The gene rpoS encodes the sigma factor sigma-38, a 37.8 kD protein in Escherichia coli. Sigma factors are proteins that regulate transcription in bacteria. Sigma factors can be activated in response to different environmental conditions. rpoS is transcribed in late exponential phase, and RpoS is the primary regulator of stationary phase genes. RpoS is a central regulator of the general stress response and operates in both a retroactive and a proactive manner: it not only allows the cell to survive environmental challenges, but it also prepares the cell for subsequent stresses (cross-protection). The transcriptional regulator CsgD is central to biofilm formation, controlling the expression of the curli structural and export proteins, and the diguanylate cyclase, adrA, which indirectly activates cellulose production. The rpoS gene most likely originated in the gammaproteobacteria.
Osmolytes are low-molecular-weight organic compounds that influence the properties of biological fluids. Osmolytes are a class of organic molecules that play a significant role in regulating osmotic pressure and maintaining cellular homeostasis in various organisms, particularly in response to environmental stressors. Their primary role is to maintain the integrity of cells by affecting the viscosity, melting point, and ionic strength of the aqueous solution. When a cell swells due to external osmotic pressure, membrane channels open and allow efflux of osmolytes carrying water, restoring normal cell volume.
In botany, drought tolerance is the ability by which a plant maintains its biomass production during arid or drought conditions. Some plants are naturally adapted to dry conditions, surviving with protection mechanisms such as desiccation tolerance, detoxification, or repair of xylem embolism. Other plants, specifically crops like corn, wheat, and rice, have become increasingly tolerant to drought with new varieties created via genetic engineering. From an evolutionary perspective, the type of mycorrhizal associations formed in the roots of plants can determine how fast plants can adapt to drought.
Phospholipase C (PLC) is a class of membrane-associated enzymes that cleave phospholipids just before the phosphate group (see figure). It is most commonly taken to be synonymous with the human forms of this enzyme, which play an important role in eukaryotic cell physiology, in particular signal transduction pathways. Phospholipase C's role in signal transduction is its cleavage of phosphatidylinositol 4,5-bisphosphate (PIP2) into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), which serve as second messengers. Activators of each PLC vary, but typically include heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca2+, and phospholipids.
Nuclear factor of activated T-cells 5, also known as NFAT5 and sometimes TonEBP, is a human gene that encodes a transcription factor that regulates the expression of genes involved in the osmotic stress.
Hortaea werneckii is a species of yeast in the family Teratosphaeriaceae. It is a black yeast that is investigated for its remarkable halotolerance. While the addition of salt to the medium is not required for its cultivation, H. werneckii can grow in close to saturated NaCl solutions. To emphasize this unusually wide adaptability, and to distinguish H. werneckii from other halotolerant fungi, which have lower maximum salinity limits, some authors describe H. werneckii as "extremely halotolerant".
Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration of electrolytes to keep the body fluids from becoming too diluted or concentrated. Osmotic pressure is a measure of the tendency of water to move into one solution from another by osmosis. The higher the osmotic pressure of a solution, the more water tends to move into it. Pressure must be exerted on the hypertonic side of a selectively permeable membrane to prevent diffusion of water by osmosis from the side containing pure water.
Chemical chaperones are a class of small molecules that function to enhance the folding and/or stability of proteins. Chemical chaperones are a broad and diverse group of molecules, and they can influence protein stability and polypeptide organization through a variety of mechanisms. Chemical chaperones are used for a range of applications, from production of recombinant proteins to treatment of protein misfolding in vivo.
Cannabis (/ˈkænəbɪs/) is commonly known as marijuana or hemp and has two known strains: Cannabis sativa and Cannabis indica, both of which produce chemicals to deter herbivory. The chemical composition includes specialized terpenes and cannabinoids, mainly tetrahydrocannabinol (THC), and cannabidiol (CBD). These substances play a role in defending the plant from pathogens including insects, fungi, viruses and bacteria. THC and CBD are stored mostly in the trichomes of the plant, and can cause psychological and physical impairment in the user, via the endocannabinoid system and unique receptors. THC increases dopamine levels in the brain, which attributes to the euphoric and relaxed feelings cannabis provides. As THC is a secondary metabolite, it poses no known effects towards plant development, growth, and reproduction. However, some studies show secondary metabolites such as cannabinoids, flavonoids, and terpenes are used as defense mechanisms against biotic and abiotic environmental stressors.
References
- ↑ Lang F (October 2007). "Mechanisms and significance of cell volume regulation". Journal of the American College of Nutrition. 26 (5 Suppl): 613S–623S. doi:10.1080/07315724.2007.10719667. PMID 17921474. S2CID 1798009.
- 1 2 Kempf, Bettina; Bremer, Erhard (October 1998). "Stress responses ofBacillus subtilis to high osmolarity environments: Uptake and synthesis of osmoprotectants". Journal of Biosciences. 23 (4): 447–455. doi:10.1007/BF02936138. S2CID 24591953.
- ↑ Sussich F, Skopec C, Brady J, Cesàro A (August 2001). "Reversible dehydration of trehalose and anhydrobiosis: from solution state to an exotic crystal?". Carbohydrate Research. 334 (3): 165–76. doi:10.1016/S0008-6215(01)00189-6. PMID 11513823.
- ↑ Burg, Maurice B.; Ferraris, Joan D. (21 March 2008). "Intracellular Organic Osmolytes: Function and Regulation". Journal of Biological Chemistry. 283 (12): 7309–7313. doi: 10.1074/jbc.R700042200 . PMC 2276334 . PMID 18256030.
- ↑ Singh, Madhulika; Kumar, Jitendra; Singh, Samiksha; Singh, Vijay Pratap; Prasad, Sheo Mohan (25 July 2015). "Roles of osmoprotectants in improving salinity and drought tolerance in plants: a review". Reviews in Environmental Science and Bio/Technology. 14 (3): 407–426. doi:10.1007/s11157-015-9372-8. S2CID 82611168.
- ↑ Crowe JH, Carpenter JF, Crowe LM (1998). "The role of vitrification in anhydrobiosis". Annual Review of Physiology. 60: 73–103. doi:10.1146/annurev.physiol.60.1.73. PMID 9558455.
- ↑ Shoriridge, Virginia D.; Lazdunski, Andrée; Vasil, Michael L. (April 1992). "Osmoprotectants and phosphate regulate expression of phospholipase C in Pseudomonas aeruginosa". Molecular Microbiology. 6 (7): 863–871. doi:10.1111/j.1365-2958.1992.tb01537.x. PMID 1602966. S2CID 24853602.
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