Psychrophilic, Psychrotrophic, and Psychrotolerant Microorganisms

Abstract

AbstractBased on temperature-dependent definition, psychrophiles are described as cold-loving microorganisms and grow optimally at about 15 °C, maximum temperature for growth at about 20 °C and minimum 0 °C or lower. Psychrotrophic microorganisms have a maximum temperature for growth about 20 °C and widespread in natural environments. Psychrotolerant microorganisms can survive at low temperature and can grow at elevated temperatures. Psychrophilic microorganisms occur in cold environments like polar surface, ice-cap regions, glaciers, cold deserts, permafrost, and deep oceans. Cold-loving bacteria include the genera Colwellia, Achromobacterium, Alcaligenes, Alteromonas, Bacillus, and many more. Physiological basis of cold adaptation includes protein synthesizing mechanisms, alteration in cellular structures, and inactivation of enzymes. Psychrophilic microorganisms produce antifreeze proteins, cryoprotectants, cold-shock proteins, and cold-active enzymes. They have applications in food industry, waste processing, agriculture, medicines, and environmental bioremediation.In India, glaciers from Indian Himalayan Ranges, cold lakes like Pangong, and high-altitude soils serve as cold environments for isolation of psychrophilic microorganisms. Cold-adapted hydrolytic enzymes have been reported from Staphylococcus lipolyticus (lipase), Actinomycetes, and Alcaligenes (amylase, xylanase, cellulase, protease). Over 20 novel species of psychrophilic microorganisms, new to Science, have been reported from India.KeywordsPsychrophilicPsychrotolerantCold lakesGlaciersCold-adapted enzymesAntifreeze proteinsCryoprotectants Colwellia Alcaligenes Indian Himalayan RangesPangong lake