Cold Adapted Fungi from Indian Himalaya: Untapped Source for Bioprospecting

Extremophiles and their expanding biotechnological applications

Microbial life is not restricted to any particular setting. Over the past several decades, it has been evident that microbial populations can exist in a wide range of environments, including those with extremes in temperature, pressure, salinity, and pH. Bacteria and Archaea are the two most reported types of microbes that can sustain in extreme environments, such as hot springs, ice caves, acid drainage, and salt marshes. Some can even grow in toxic waste, organic solvents, and heavy metals. These microbes are called extremophiles. There exist certain microorganisms that are found capable of thriving in two or more extreme physiological conditions simultaneously, and are regarded as polyextremophiles. Extremophiles possess several physiological and molecular adaptations including production of extremolytes, ice nucleating proteins, pigments, extremozymes and exopolysaccharides. These metabolites are used in many biotechnological industries for making biofuels, developing new medicines, food additives, cryoprotective agents etc. Further, the study of extremophiles holds great significance in astrobiology. The current review summarizes the diversity of microorganisms inhabiting challenging environments and the biotechnological and therapeutic applications of the active metabolites obtained as a response to stress conditions. Bioprospection of extremophiles provides a progressive direction with significant enhancement in economy. Moreover, the introduction to omics approach including whole genome sequencing, single cell genomics, proteomics, metagenomics etc., has made it possible to find many unique microbial communities that could be otherwise difficult to cultivate using traditional methods. These findings might be capable enough to state that discovery of extremophiles can bring evolution to biotechnology.

Improving the Growth and Productivity of Macrotyloma uniflorum Medicinal Plant by the Co-inoculation of P, Zn and K-Solubilizing Fungi Under Field Conditions

The presence of small amount of soluble forms of Phosphorus (P), Potassium (K) and Zinc (Zn) in most soils is one of the limiting factors for agronomic crop production. The current study focuses on Macrotyloma uniflorum (horse gram or gahat), the most commonly cultivated crop in Uttarakhand. The current initiative and study were started, because there is a little information available on the impact of co-inoculation of beneficial fungi on crops in agricultural fields. Aspergillus niger K7 and Penicillium chrysogenum K4 were isolated and selected for the study on the basis of in vitro P, K and Zn-solubilizing activity. The solubilizing efficiency of K4 strain was 140% and K7 was 173.9% for P. However, the solubilizing efficiencies of K4 and K7 were 160% and 138.46% for Zn and 160% and 466% for K, respectively. The field trials were performed for two consecutive years, and growth and yield related parameters were measured for evaluation of the effect of P, K and Zn-solubilizing fungal strains on the crop. All the treatments showed a significant (P < 0.05) increase in growth and yield of M. uniflorum plants over uninoculated control; however, the best treatment was found to be soil inoculated with P. chrysogenum K4 + A. niger K7 in which the yield was enhanced by 71% over control. Thus, the co-inoculation of K4 and K7 strains showed a great potential to improve the growth and yield of plants. Both the fungal strains simultaneously solubilized three important nutritional elements in soil, which is a rare trait. Moreover, the capacity of these fungal strains to enhance the plant root nodulation and microbial count in soil makes the co-inoculation practice quite beneficial for sustainable agriculture.

A reduction in temperature induces bioactive red pigment production in a psychrotolerant Penicillium sp. GEU_37 isolated from Himalayan soil

Filamentous fungi are being globally explored for the production of industrially important bioactive compounds including pigments. In the present study, a cold and pH tolerant fungus strain Penicillium sp (GEU_37), isolated from the soil of Indian Himalaya, is characterized for the production of natural pigments as influenced by varying temperature conditions. The fungal strain produces a higher sporulation, exudation, and red diffusible pigment in Potato Dextrose (PD) at 15 °C as compared to 25 °C. In PD broth, a yellow pigment was observed at 25 °C. While measuring the effect of temperature and pH on red pigment production by GEU_37, 15 °C and pH 5, respectively, were observed to be the optimum conditions. Similarly, the effect of exogenous carbon and nitrogen sources and mineral salts on pigment production by GEU_37 was assessed in PD broth. However, no significant enhancement in pigmentation was observed. Chloroform extracted pigment was separated using thin layer chromatography (TLC) and column chromatography. The two separated fractions i.e., fractions I and II with Rf values 0.82 and 0.73, exhibited maximum light absorption, λ_max, at 360 nm and 510 nm, respectively. Characterization of pigments using GC-MS showed the presence of the compounds such as phenol, 2,4-bis (1,1-dimethylethyl) and eicosene from fraction I and derivatives of coumarine, friedooleanan, and stigmasterole in fraction II. However, LC-MS analysis detected the presence of derivatives of compound carotenoids from fraction II as well as derivative of chromenone and hydroxyquinoline as major compounds from both the fractions along with other numerous important bioactive compounds. The production of such bioactive pigments under low temperature conditions suggest their strategic role in ecological resilience by the fungal strain and may have biotechnological applications.

Potential of Halophilic Penicillium chrysogenum Isolated from Algerian Saline Soil to Produce Laccase on Olive Oil Wastes

Enzymes from halophilic fungi offer interesting biotechnological applications, which lead us to explore novel producing strains. 23 fungi were isolated from Algerian saline soil. Among the three strains presenting laccase activities, one exhibited the high decolourising capacity of olive mill wastewaters. Identification showed that the efficient isolate GS15 belongs to Penicillium chrysogenum. This strain achieves optimal growth at 15% NaCl, 25 °C, pH 5, dark, aerobic and static conditions. The selected fungus is capable of producing extracellular enzymes as follows: caseinase, tannase, esterase and lipase. The laccase activities produced by P. chrysogenum on raw olive wastes are being reported here for the first time. GS15 produced 183.0 and 203.0 U/L of laccase activities in 10% and 20% unsupplemented olive mill wastewaters, respectively. The significant enzymatic activities can be correlated to the high ability of GS15 to decolourise industrial wastewater from the olive oil extraction. In these conditions no pre-treatment of olive wastewaters was needed. On the untreated grinded and non-grinded olive pomace, the laccase activity was 5.78 U/g and 5.36 U/g, respectively. Because the halophilic fungus has basic requirement for growth, this fungal strain is promising for saline biotechnological applications.

Fighting plant pathogens with cold-active microorganisms: biopesticide development and agriculture intensification in cold climates

Cold-adapted (CA) microorganisms (= psychrophiles or psychrotolerants) are key players of many ecological interactions in natural ecosystems. Some of them can colonize the rhizosphere of plants and cause damage to their hosts; others, on the contrary, protect plants from their pathogens through direct and indirect mechanisms, thus promoting plant growth and development. These "protective" microbes are known as biocontrol agents (BCA). BCA either limit or inhibit the growth of plant pathogens, owing to the excretion of a panoply of secondary metabolites (including soluble and volatile antibiotics, siderophores, quorum sensing interfering agents). BCA can also control plant pathogens through indirect mechanisms, including competence for nutrients and space, or else by interfering with their chemical communication. That explains why some of these BCA have been included in the formulation of commercial biopesticides, which are environmentally friendly products containing live cells used to control plant diseases and pests. At present, the development of biopesticides from mesophilic microorganisms is an established technology. Unfortunately, these biopesticides are not active at low temperatures. On the other hand, the information concerning the potential use of CA-BCA for the same goal is at its infancy. Here, we review the current knowledge concerning the isolation, identification, and characterization of CA microbes which act as antagonists of plant pathogens, including the mechanisms they deploy to antagonize plant pathogens. We also illustrate their biotechnological potential to develop CA biopesticides and discuss their utility in the context of mountainous agriculture. KEY POINTS: • Many naturally occurring cold-active microbes antagonize plant pathogens. • The mechanisms of biocontrol exerted by these microbes are either direct or indirect. • Cold-active biocontrol agents can be used to develop biopesticides. • Cold-active biopesticides are crucial for sustainably intensifying agriculture in cold climates.

Microbial Ecology from the Himalayan Cryosphere Perspective

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.

Bioprospecting cold-adapted plant growth promoting microorganisms from mountain environments

Mountain soils are challenging environments for all kinds of living things, including plants and microorganisms. Many cold-adapted microorganisms colonizing these extreme soils play important roles as promoters of plant growth and development; for that reason, they are called collectively plant growth-promoting microorganisms (PGPM). Even though there is seldom doubt concerning the usefulness of PGPM to develop eco-friendly bioinoculants, including biofertilizers and biocontrollers, a series of aspects need to be addressed in order to make this technology field-applicable. Among these aspects, the ecological and rhizosphere competences of PGPM are of paramount importance, particularly when considering the development of bioinoculants, well suited for the intensification of mountainous agricultural production. Studies on native, cold-adapted PGPM conducted in the Indian Himalayan region (IHR) and the Tropical Andes (TA) lead nowadays the research in this field. Noticeably, some common themes are emerging. For instance, soils in these mountain environments are colonized by many cold-adapted PGPM able to mobilize soil nutrients and to inhibit growth of plant pathogens. Studies aimed at deeply characterizing the abilities of such PGPM is likely to substantially contribute towards a better crop productivity in mountainous environments. The present review focuses on the importance of this microbial resource to improve crop productivity in IHR and TA. We also present a number of successful examples, which emphasize the effectiveness of some bioinoculants-developed from naturally occurring PGPM-when applied in the field.