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Exopolysaccharides of Halophilic Microorganisms: An Overview
Published in Devarajan Thangadurai, Jeyabalan Sangeetha, Industrial Biotechnology, 2017
Pradnya P. Kanekar, Siddharth V. Deshmukh, Sagar P. Kanekar, Prashant K. Dhakephalkar, Prabhakar K. Ranjekar
Halophiles are the salt loving microorganisms that thrive in hypersaline environments originated mostly by evaporation of seawater. They include both prokaryotic and eukaryotic microorganisms having ability to balance the osmotic pressure of the surrounding environment and resist denaturing effects of salt. Their metabolic types represent oxygenic and anoxygenic phototrophs, aerobic heterotrophs, sulfate and nitrate reducing organisms, etc. They are classified based upon their requirement of salt as halotolerant (0%, salt tolerance upto 15%), slight halophiles (2–5%), moderate halophiles (5–15%) and extreme halophiles (20–30%) (Kushner, 1993). Moderately halophilic bacteria constitute a heterogenous physiological group of microorganisms belonging to different genera while extreme halophiles are the archaea belonging to family Halobacteriaceae. Halotolerant organisms grow in absence of salt as well as in high salinity condition. Halophilic microorganisms have been isolated from environments including aquatic habitats of both high-and low salinity, salty marshy places, saline lakes (Javor, 1989), from Dead Sea (Oren, 2002). They are reported from ancient salt sediments as reviewed by Grant et al. (1998) and McGenity et al. (2000). Halococcus salifodinae was the first strain isolated from ancient rock salt (Permian salt sediment) by Denner et al. (1994). Haloarchaea were further reported from ancient rock salt (Stan Lotter et al., 1999; Stan Lotter et al., 2002; Vreeland et al., 2002; Gruber et al., 2004). Halophilic microorganisms have been isolated from a number of hypersaline ecosystems, for example, the Great Salt Lake, Utah, USA, the Dead Sea, the extremely alkaline brines of the Wadi Natrun, Egypt and Lake Magadi, Kenya (Oren, 1994; Kamekura, 1998).
Extremophilic Microbes
Published in Ajar Nath Yadav, Ali Asghar Rastegari, Neelam Yadav, Microbiomes of Extreme Environments, 2021
Aathira Sreevalsan, Jamseel Moopantakath, Ranjith Kumavath
Nanoparticles have shown to increase the delivery precision of various drugs and nutraceuticals with several biological applications. Drug delivery with the aid of specific nanoparticles provide enhanced availability of the drug in localized tissue without adverse effects to the normal function of the cells (Shen et al. 2016; Huang et al. 2015). These are lipophilic molecules, fat-soluble vitamins A, D, E and K, polysaturated lipids and phytochemicals usually used for dissolution mechanisms of nutraceuticals via nanoparticle formulations (Acosta 2009; McClements 2015). Halotolerant organisms are classified based on the domain known as halotolerant bacteria and haloarchaeal species. Halobacteria are bacteria, which can survive salt conditions and haloarchaea, bloom at extreme salt conditions represented among the Halobacteriaceae family, Euryarchaeota phylum, Archaea domain (Gunde-Cimerman et al. 2018). Halotolerant organisms have an excellent ability to adjust from low to higher salt concentration under external environment, while the halophilic archaeal organisms are frequently observed at high salinities for proper growth and metabolism (Oren et al. 2001). They are most extensively observed in salt lakes, brines, saline soils, cold saline habitat and saline food products (Singh et al. 2019). Based on the salt concentration required for optimum growth, these can be differentiated into three class (Thombre et al. 2016). Microorganisms have become one of most promising organisms for synthesizing pigments such as chlorophyll and carotenoids. Interestingly carotenoids synthesized through the isoprenoid pathway are found to be a biologically active compound against cancer and microbial infection (Nisar et al. 2015). Carotenoids are C40–C50 hydrophobic compounds with a long conjugated double bond, bilaterally symmetrical around the central double bond including the colour ranging from red, orange, yellow or even colourless (Mackinnon et al. 2011). With the appearance of oxygen and chemical compositions, carotenoids can be classified into carotenes or carotenoid hydrocarbons containing carbon and hydrogen atom alone and oxygenated carotenoids such as xanthophyll containing oxygenated mixtures with methoxy, carboxylic or additional functional groups (Rivera et al. 1998) (Fig. 12.1).
Bioelectricity production and desalination of Halomonas sp. – the preliminary integrity approach
Published in Biofuels, 2019
R. Uma Maheswari, C. Mohanapriya, P. Vijay, K.S. Rajmohan, M. Gopinath
Halophiles are salt-loving bacteria, and can be classified as slightly halophile, moderately halophile, and extremely halophile based on the concentration of sodium chloride present in the environment. Halophiles are distributed all over the world in hypersaline environments – specifically, natural hypersaline brines in arid, coastal and even deep-sea locations, as well as in artificial salterns used to mine salts from the sea. The novel behavior of these halophiles and the potential for large-scale culturing means halophiles find wide application in biotechnology. Halophiles are distinguished by their need for hypersaline conditions for growth. They may be classified according to their salt requirements: slight halophiles grow optimally at (2–5%) sodium chloride; moderate halophiles grow optimally at (5–20%) sodium chloride; and extreme halophiles grow optimally above (20–30%) sodium chloride. In contrast, non-halophiles grow optimally at less than 2% sodium chloride. Many halophile and halotolerant microorganisms can grow and withstand a high salt concentration with the requirement or tolerance for salts sometimes based on nutritional factors present in the environment [11].
Role of halotolerant and chitinolytic bacteria in phytoremediation of saline soil using spinach plant
Published in International Journal of Phytoremediation, 2020
Muhammad Anees, Arshad Qayyum, Muhammad Jamil, Fayyaz ur Rehman, Muhammad Abid, Muhammad Saqib Malik, Muhammad Yunas, Kalim Ullah
Reclamation of saline soils to improve crop productivity using novel biotechnological tools such as bioremediation offers one of the acceptable alternatives to the chemical application for the purpose. Halotolerant bacteria are those which can grow in high salt conditions as well as in non-saline conditions. Mostly they adopt various mechanisms in salty areas such as production of exopolysaccharides, stress proteins, restricted entry or efflux of Na+, and sodium-dependent potassium uptake (Apte and Bhagwat 1989; Goel et al. 1997). The halotolerant bacteria may be used for the bioremediation of saline soils and degradation of toxic compounds (Arora et al.2014). Moreover, the bacteria may also help plants evade salt stress, for instance, by production of ACC deaminase (Ramadoss et al. 2013). In addition to this, a bacterial strain with multiple characters that may or may not be directly related to each other, but however, supporting toward the plant and at the end boosts the plant growth can always be interesting to quest for. A halotolerant chitinolytic bacterial strain can be an example in that case, helping salt remediation as well as combating the plant pathogens/pests. The chitinolytic bacteria have the ability to counter the fungal plant diseases and improve plant growth (Naing et al.2014; Anees et al. 2019). Chitinases are the enzymes that can hydrolyze the chitin present in the fungal walls. A similar way can be to try together the two types of bacteria to get the favorable results which was one of the reasons why the present study was conducted. A few supporting documents can be found in the literature such as the amendment of soil with chitin boosting the chitinolytic soil microbiome was found to increase the rate of bioremediation of soils contaminated with heavy metals (Rae and Gibb 2003). It was reported that Virgibacillus marismortui species produced chitinases and had a halotolerant nature as well (Essghaier et al.2012).