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Extremophiles for Sustainable Bio-energy Production
Published in Pratibha Dheeran, Sachin Kumar, Extremophiles, 2022
Amit Verma, Tirath Raj, Shulbhi Verma, Varun Kumar, Ruchi Agrawal
Microorganisms that colonized in cold environments (cold adapted) under 15-20°C (from deep sea to mountains and Polar Regions) are designated as psychrophiles. Besides natural environments, these microorganisms are also colonized in human-made low temperature places like deep freezers. Psychrophiles living in ocean depth are known as Piezo-psychrophiles and psychrophiles inhabiting elevated salt concentrations are designated as Halo-psychrophiles (Kumar et al. 2011). Psychrophiles include a variety of microorganisms like Gram-positive and Gram-negative bacteria, fungi, yeast and microalgae. Not only cold environment, the Polar Regions also have other extreme conditions like strong ultraviolet radiation, robust winds and dryness. In such harsh conditions, psychrophiles support their life by producing special antifreeze proteins, UV protecting compounds, polyunsaturated fatty acids and various antioxidants (Kim et al. 2020, Jung et al. 2014, Nogueira et al. 2015). In cold temperature, psychrophiles also faced the challenges of lack in thermal energy and problem of high viscosity and to overcome these problems, protein modification is induced by chaperones and cold-shock proteins in cells (D’Amico et al. 2006). The enzyme proteins remain active by flexible structure and by lowering the enthalpy-driven interactions (Violot et al. 2005, Berger et al. 1996). The fluidity of membranes is maintained by high amount of polyunsaturated, unsaturated and methylbranched fatty acids (Chintalapati et al. 2004). From metabolism point of view, psychrophiles maintain ATP generation and cofactors production by enhancing the activities or up-regulating enzymes of central metabolic pathways (Russell 2000).
Interconnection between PHA and Stress Robustness of Bacteria
Published in Martin Koller, The Handbook of Polyhydroxyalkanoates, 2020
Stanislav Obruca, Petr Sedlacek, Iva Pernicova, Adriana Kovalcik, Ivana Novackova, Eva Slaninova, Ivana Marova
The effect of low temperatures on microbial cell depends upon the fact of whether or not the temperature decreases below 0°C. Above this breakpoint the bacterial cells are usually capable of active defense against the stress conditions which typically include the formation of cold shock proteins and other specific metabolites which enable them to cope with low temperatures. Nevertheless, when the temperature drops to values where water starts freezing, the response of most prokaryotes is passive, frequently leading slowly to the death of cells [43]. The growth of extracellular ice crystals increases the osmotic pressure in the medium since the excluded solutes are concentrated in a decreasing volume of water. This effect leads to so-called “freeze dehydration”, and has harmful consequences for challenged cells. Further, the cells are subsequently damaged by the formation of intracellular ice crystals which might damage membranes and organelles, and cause the formation of gas bubbles. Beside freeze dehydration and intracellular ice, cells can also be damaged by reactive oxygen species (ROS) formed in cells during freezing [44] and the decreasing volume of the bacteria-inhabited channels of unfrozen liquid surrounded by growing ice crystals can lead to mechanical injury of the cells [45]. Mesophiles, unlike psychrophiles, do not tolerate cold conditions well. The exposure of mesophiles to near-freezing temperatures usually results in reduced enzyme activity, decreased membrane fluidity, altered transport of nutrients and waste products, decreased rates of transcription, translation and cell division, protein cold-denaturation, inappropriate protein folding and intracellular ice formation [41]. On the other hand, the microorganisms, which can grow and maintain their vital metabolic functions in cold environments ranging from −20°C to +10°C, are known as psychrophiles. Different strategies could contribute to the accommodation of microorganisms to a cold environment, such as environmental selection, and modifications at the molecular or physiological level [46].
Microbes from Cold Deserts and Their Applications in Mitigation of Cold Stress in Plants
Published in Ajar Nath Yadav, Ali Asghar Rastegari, Neelam Yadav, Microbiomes of Extreme Environments, 2021
Murat Dikilitas, Sema Karakas, Eray Simsek, Ajar Nath Yadav
When cold-adapted organisms were defined, two types of terms have been used. These are psychrophiles and psychrotrophs. The term psychrophiles were defined as the microorganisms growing around 15°C or less (Moyer and Morita 2007). They include gram-negative bacteria such as Pseudoalteromonas, Moraxella, Psychrobacter, Flavobacterium Polaromonas, Psychroflexus, Polaribacter, Moritella, Vibrio and Pseudomonas; Gram-positive bacteria such as Arthrobacter, Bacillus and Micrococcus species and several yeasts, fungi and microalgae species (Feller and Gerday 2003; Berg et al. 2019). Psychrophiles grow at or below zero (0°C) and have an optimum growth temperature at 15°C and an upper limit of 20°C. In contrast, psychrotolerant microorganisms are able to grow between 0–30°C, and are also considered as cold-tolerant mesophiles (Morita 1975). Cold-tolerant microorganisms have strong metabolisms to reduce the negative effects of cold. Low temperatures primarily affect the lipid bi-layer of the bacterial cell making it impermeable to the diffusion of solutes, which helps the cell function properly. This is achieved by an increase in the amount of branched fatty acid and a decrease in cyclic fatty acids with the growth of monounsaturated straight-chain fatty acids. Cold acclimation proteins are produced by cold-tolerant bacteria in which a large amount of proteins are produced during continuous growth at low temperatures. On the other hand, Cold-shock proteins (Csp) are initiated by a sudden decrease in temperature (Piette et al. 2011). Ice nucleators are proteins which either limit supercooling or induce freezing at temperatures below 0°C by mimicking the structure of an ice crystal surface. They impose an ice crystal-like arrangement on the water molecule with their surface and reduce the necessity of energy for the initiation of ice formation (Zachariassen and Kristiansen 2000). These proteins are involved in maintaining some metabolic functions at low temperatures by replacing cold-denaturated peptides. Psychrophiles also produce cold-adapted enzymes that have high specific activities at low temperatures (Mishra et al. 2010).
Biotransformation of chemically dispersed diesel at sub-zero temperatures using artificial brines
Published in Environmental Technology, 2021
Nga Phuong Dang, Chris Petrich, Megan O’Sadnick, Lisa Toske
Sea ice is a habitat for both psychrophilic and psychrotrophic microorganisms, especially psychrophiles. Psychrophilic microorganisms possess cold-active enzymes which can be up to 10 times more active at low and moderate temperatures as compared to their mesophilic homologs, which allow them to survive under such low-temperature condition [1]. Microbial activities have been measured at the temperatures close to freezing point of water and in marine ice at a temperature lower than −10°C, indicating that slow hydrocarbon biodegradation occurs in oil-contaminated ice [2]. Very few studies, however, have focused on biodegradation of oil in sea ice and how sea-ice microorganisms respond to the presence of oil [3–8]. Gammaproteobacteria became the predominant phylotype in oil-contaminated sea ice from both Svalbard [3,4] and bottom sea ice from Canadian Arctic Archipelago [5] which included bacterial genera such as Marinobacter, Shewanelle, and Pseudomonas [3] and Colwellia, Marinomonas, and Glaciecola [4].
Isolation and characterization of a cold-active, alkaline, detergent stable α-amylase from a novel bacterium Bacillus subtilis N8
Published in Preparative Biochemistry and Biotechnology, 2018
Psychrophiles, in other words cold-adapted microorganisms, can survive in cold environments. While psychrophiles optimally grow below 15°C, the optimum growth temperature range for psychrotolerant microorganisms (or psychrotrops) is 20–25°C.[12,13]Bacillus species are the major microbial sources of the amylases that are active in cold conditions.[14,15] Cold-active enzymes from cold-adapted microorganisms have advantages like reducing energy consumption and wear and tear[8,12] and offering potential economic benefits.[7] The cold-active enzymes are especially being preferred in laundry and dish-washing detergents because of their eco-friendly characters and low-temperature washing properties.