Cold-adapted microorganisms represent a large fraction of biomass on Earth because of the dominance of low-temperature environments. Extreme cold environments are mainly dependent on microbial activities because this climate restricts higher plants and animals. Himalaya is one of the most important cold environments on Earth as it shares climatic similarities with the polar regions. It includes a wide range of ecosystems, from temperate to extreme cold, distributed along the higher altitudes. These regions are characterized as stressful environments because of the heavy exposure to harmful rays, scarcity of nutrition, and freezing conditions. The microorganisms that colonize these regions are recognized as cold-tolerant (psychrotolerants) or/and cold-loving (psychrophiles) microorganisms. These microorganisms possess several structural and functional adaptations in order to perform normal life processes under the stressful low-temperature environments. Their biological activities maintain the nutrient flux in the environment and contribute to the global biogeochemical cycles. Limited culture-dependent and culture-independent studies have revealed their diversity in community structure and functional potential. Apart from the ecological importance, these microorganisms have been recognized as source of cold-active enzymes and novel bioactive compounds of industrial and biotechnological importance. Being an important part of the cryosphere, Himalaya needs to be explored at different dimensions related to the life of the inhabiting extremophiles. The present review discusses the distinct facts associated with microbial ecology from the Himalayan cryosphere perspective.

Production of laccase by a cold and pH tolerant strain ofPenicillium pinophilumhas been investigated under different cultural conditions for up to 35 days of incubation. The fungus was originally isolated from a low temperature environment under mountain ecosystem of Indian Himalaya. The estimations were conducted at 3 temperatures (15, 25, and 35°C), a range of pH (3.5–11.5), and in presence of supplements including carbon and nitrogen sources, vitamins, and antibiotics. Optimum production of laccase was recorded at 25°C (optimum temperature for fungal growth) and 7.5 pH. The production of enzyme was recorded maximum on day 28 (11.6±0.52 U/L) following a slow decline at day 35 of incubation (10.6±0.80 U/L). Fructose and potassium nitrate (0.2%) among nutritional supplements, chloramphenicol (0.1%) among antibiotics, and folic acid (0.1%) among vitamins were found to be the best enhancers for production of laccase. Relatively lower but consistent production of laccase for a longer period is likely to be an ecologically important phenomenon under low temperature environment. Further, enhancement in production of enzyme using various supplements will be useful for its use in specific biotechnological applications.

Extreme thermal environments, both natural (e.g., hot springs, fumaroles, geysers, mud pots, deep-sea hydrothermal vents) and man-made (e.g., compost heaps, sawdust, coal refuse piles), are rich sources of thermophilic microorganisms, including Bacteria and Archaea. These organisms possess unique adaptations that allow survival and metabolic activity at elevated temperatures, making them valuable sources of thermostable and thermoactive enzymes. This review synthesizes current knowledge on thermophiles, including their phylogeny, adaptation mechanisms, and cultivation strategies. We discuss the industrial applications of thermozymes, such as DNA polymerases and other thermostable enzymes, and highlight the role of genomics, systems biology, and bioinformatics in accelerating enzyme discovery. The review also addresses the astrobiological relevance of thermophiles as models for life in extreme extraterrestrial environments and emphasizes the importance of conservation and sustainable use of natural thermal habitats. Collectively, this overview provides a comprehensive perspective on the ecological, biotechnological, and fundamental research significance of thermophiles and their enzymes.