Microbial Ecology from the Himalayan Cryosphere Perspective

Abstract

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.

Keywords: Himalaya; cold tolerant microorganisms; cryosphere; microbial communities.

Figure 1

Geographical distribution of Himalayan ranges (Source: ICIMOD (International Centre for Integrated Mountain Development), Nepal).

Figure 2

To maintain cellular integrity and functionality, cold-loving microbial cells possess some extraordinary features—a: increase in unsaturated fatty acids against desiccation, b: RNA binding proteins (RBP) help to retain the RNA primary structure to support expression, c, d: Accumulation of cryoprotectants and functioning of cold-active enzymes support homeostasis and growth in stressed environments, e: inhibition of ice crystal formation protects the cell from damage at low temperatures.

Figure 3

Ecological processes regulated by cold-adapted microorganisms in different ecosystems. (a) Biogeochemical cycles in the barren lands of glacial regions (>3500 m asl). (b) Nutrient cycles/energy flow in the high-altitude forests. (c) Agriculture system under the low-temperature regions of mountains (Photo credit: Khashti Dasila).

Figure 4

Conversion of different forms of carbon through microbial activities under the biodegradation process.