The microbes may also exist as cell clusters. Microbes are not limited to only eubacteria and archaea but also includes members from fungi, protozoa, algae, and viruses. Ribosomal RNA is considered a crucial molecule to draw an authentic classification of the life forms. On the basis of comparative rRNA sequence analysis, a basal universal phylogenetic tree had been inferred by Carl Woese [1], representing the overview of organismal history. This phylogenetic tree hypothesized the common origin of all forms of life, emphasizing the importance of microorganisms in the biological diversity at the Earth.
The global compilation of microbiological data has estimated the existence of about 1 trillion microbial species at the Earth [2]. The Earth Microbiome Project had been established in the year 2020, with the main objective to document the uncultured microbial diversity and the functional potential thereof [3]. In the project, sampling of the Earth's microbial communities is being done on an unprecedented scale. Recently, a total of 27 751 samples had been collected from 43 countries to characterize the microbial communities of diverse physicochemical properties and exposed to a wide range of biotic and abiotic factors [4].
1.1.2 Bioprospecting
Bioprospecting is the excavation of useful genetic or biochemical materials from natural resources [5]. The word “bio‐” refers to “organism” and “prospecting” refers to the search for precious material. Bioprospecting of the microbial population, residing in diverse ecological niches, is gaining more and more attention with the increasing demand for bioactive molecules and nutraceuticals of pharmaceutical, food, and agro‐industrial significance. Microorganisms exist in every corner of this planet, and many of them may not be cultivated. Bioprospecting of biologicals, including microbes, requires interdisciplinary knowledge to exploit the natural resource for societal benefits in a sustainable manner.
A major proportion of Earth contains extreme environmental, where most of the life forms cannot survive. However, extremophiles, which evolve a natural mechanism to thrive the harsh condition, are considered a rich biological resource for extremophiles [6]. The bioactive compounds and the extremozymes have great industrial importance [7]. There is an enormous genetic pool of microbes co‐evolved with the higher organisms, including plants and animals. They have manifold promising biomolecules of industrial importance [5]. There are boundless opportunities to explore the treasure box to meet the growing demand for novel bioactive molecules, e.g., food ingredients, agrochemicals, functional biomolecules, antibiotics, enzymes, and so on. Omics is a compelling approach for the exploration of various niches of diverse environmental conditions and the discovery of unusual novel enzymes and other metabolites of human use [8].
1.1.3 Bioprospection of Microorganisms
The microbial resources have potential in the generation of a wide range of high‐value compounds. This section has explained a few specific examples, the detail of which can be found in the subsequent chapters.
Biosurfactants are used in many fields, such as water treatment, food processing, health, disinfectants, cosmetics, and medicines [9]. Most biosurfactants are produced employing different strains of bacteria, yeast, and molds [10]. The uses of biosurfactants of microbial origin have been demonstrated in various purposes, for example in food processing, water treatment, cosmetics and pharmaceuticals, and bioremediation.
Microbial gum is a polysaccharide molecule mostly produced by bacteria and fungi [11]. These molecules protect the microbes from harsh environmental conditions [12]. These compounds are of widespread use in foods, pharmaceuticals, and cosmetics. The microbial gums are of prebiotic nature. Its uses have also been demonstrated in wound healing and carrier for drug delivery [13]. The demand for microbial gums is steadily increasing in various industries.
The practicality and potential of microbes in cosmetics have been well established. The use of antiaging products is in the spotlight. A variety of cosmetic compounds are produced from cultured microorganisms such as bacteria, yeasts, fungi, and algae [14]. Many compounds, including antioxidants, peptides, and proteins, hold a promising future in the cosmetic skincare sector. Natural compounds not only have the ability to attract the attention of the market but also have valuable properties of potential medical benefits. In this regard, it is necessary to mine a variety of natural resources for novel compounds. The demand for antiaging and whitening products is expected to steadily increase annually [15].
The microbial population is also useful in cleaning of the environment via bioremediation approach. The metabolic activities of many microorganisms have been found to convert unwanted pollutants into harmless compounds [16]. Many fungal strains have been identified that have nonspecific ability to break down various pollutants. Intensive researches have been conducted to highlight the enzymatic systems involved in bioremediation in order to develop and optimize the bioremediation processes [17]. Microbial interference in addressing the issues related to environmental pollution could offer economically viable and socially acceptable solution. An integration of microorganisms and electrochemical systems has led to developing green technologies that could generate power from wastewater or polluted soils [18, 19]. Microbial strains have been characterized for the development of bioplastic. For example, poly(lactic acid), a bioplastic molecule, can be produced by the microbial fermentation of starch biomass [20]. Development of microbial biotechnology for the production of bioplastic could prevent pollution at a greater extent. Furthermore, microbial communities play critical roles in transforming the abundant agri‐biomass into energy products such as biohydrogen, biogas, bio‐oil, bioethanol, biodiesel, biofuels, and so on [21, 22]. There is a rapid increase in the interest in using biomethane as a fuel for a variety of applications such as boilers, engines, gas turbines, and fuel cells.
Carbohydrates are one of the most critical nutrients in food. However, in recent years, excessive consumption of glucose and fructose has been linked to obesity and diabetes across the world. Many microbial metabolites of sweet nature and reduced calorie are being explored for their use as a substitute of sugar as food ingredients, e.g. rare sugars – D‐allulose, tagatose, turanose, kojibiose, erythritol, and so on [23–25]. These are rare sugars, the monosaccharides that are found in nature only in minute quantities. The microbial resource can be explored for the biotechnological production of more than 50 different rare sugars [26]. Furthermore, microorganisms are a rich bioresource for production of various kinds of oligosaccharide molecules of reduced calorie and prebiotic function [27].
Agriculture today relies on the extensive use of pesticides and fungicides. There is currently a consumer preference to reduce the use of synthetic organic chemicals used in the agricultural treatments. Microbe‐derived organic compounds have been experienced very effective and environment friendly. Such compounds have been reported to protect plants from pathogens and provide a better environment for crop growth [28].
Apart from the above, many microbial compounds of medicinal importance have gained attention in the industrial market. Penicillin is a traditional example of microbial importance for the development of therapeutic drug molecules. One of the brilliant examples of bioprospection is the study that received the Nobel Prize in the year 2015. The research was a series of studies by Dr. Omura team, who developed Avermectin and Ivermectin, which are now utilized as drugs and pesticides against parasitic worms, insect pests, and other pathogens [29, 30]. Many microbial proteins, peptides, and metabolites of anticancerous ability have been reported in many studies [31, 32].
1.2 Conclusions and Perspectives
Microbial diversity is a very crucial resource for the execution of exploitable biology. Bioprospection of microbial resource facilitates the identification and isolation of high‐value molecules of desirable activity. Researches are being conducted to exploit the microbial diversity, obtaining the biomolecules of pharmaceutical, bioceutical, agricultural, bioremediation, etc., significance. Microorganisms should be exploited as cell factories for the production of biomolecules of health significance, antibiotic, anti‐insecticidal compounds, biosurfactants, biofilm, etc. The use of microorganisms should be validated for their meaningful contribution toward food security and bioremediation. Microbial prospecting is required to be intensified with systematic and sustainable approaches.