Actinomycetes are bound with bacteria in the same class of Schizomycetes but confined to the order Actinomycetales (Kumar et al., 2005).
The actinomycetes are a group of bacteria which possess many important as well as interesting features. They have substantial value as producers of antibiotics and of other therapeutically useful compounds. They exhibit various ranges of life cycles which are unique among the prokaryotes and appear to play a major role in the cycling of organic matter in the soil ecosystem (Veigaet al., 1983). Thus it holds a prominent position due to their diversity and proven ability to produce new compounds, because discovery of novel antibiotic and non-antibiotic lead molecules through microbial secondary metabolite screening is becoming increasingly important.
They are unicellular likewise bacteria, but they also produce mycelium which is non septate (coenocytic) and more slender, like true bacteria they do not have distinct cell wall and their cell wall is without chitin and cellulose (commonly present in the cell wall of fungi). Unlike slimy distinct colonies of true bacteria which grow quickly on culture media actinomycetescolonies show slow gowth, show powdery consistency and firmly stick to agar surface. They produce hyphae and conidia or sporangia like fungi. Some Actinomycetes whose hyphae undergo segmentation resembles bacteria, both by morphologically and physiologically. Actinomycetes are numerous and widely distributed in soil, compost etc and are next tobacteria in abundance. Plate count estimates gives value ranging from 10^4 to 10^8 per gram of soil. They are sensitive to acidity or low pH (optimum pH range is within 6.5 to 8.0) and waterlogged soil conditions. As we go deep into the soil, the population of actinomycetesincreases. They are aerobic (requires oxygen), heterotrophic (cannot make its own food) and mesophilic (25-30ºC) organisms and some