Diversity and Biotechnological Potential of Culturable Rhizospheric Actinomicrobiota

Abstract

The interface of plant root and soil is the most active region where major parts of maximum number of cycles occur that leads to the accumulation of diverse chemicals of microbial origin. Soil is one of the most diverse terrestrial ecosystems. Within soil, rhizosphere is the most active fraction where interaction between biotic and abiotic components attracts enumerable microorganisms. Thus rhizosphere becomes the important hotspot of biotechnological interest. The root secreted compounds play significant roles either as chemo attractants or as repellants in the rhizospheric region immediately surrounding the root system. Plant root exudates are able to control the soil microbial community in their immediate proximity; interact with herbivores, i.e., primary consumers; encourage positive interactions like beneficial symbioses; influence some physicochemical soil parameters; and also restrict the growth of competitor species. Root-microbe cross talk are either positive, i.e., mutualistic to the plant, or negative, i.e., antagonistic to the plant species. Members of phylum actinobacteria are widely distributed in nature and have been isolated from several extreme environments (drought, high temperatures, pressure, pH, salinities) and are associated with plants growing in different habitats. Actinobacteria are of agricultural importance as they can promote plant growth and improve nutrition of plant by direct plant growth-promoting mechanisms, like fixation of nitrogen; solubilization of phosphorus, potassium, and zinc; production of plant growth promotors; and ACC deaminases, or by indirect mechanisms such as the production of ammonia, antibiotics, hydrogen cyanide, lytic enzymes, and siderophores.