Screening of bacteria Streptomyces Waksman and Henrici 1943 (Streptomycetaceae) Isolates from Soil Samples in Iraq

Background: The genus Streptomyces Waksman & Henrici 1943 includes aerobic, gram-positive, and filamentous bacteria which produce well developed vegetative hyphae with branches. The wall consists of a large mixture of different compounds, including peptidoglycan, teichuronic acid, teichoic, and polysaccharides. The peptidoglycan components consist of glycan as a chains of irregular N-acetyl- d-muramic acid (NAM), diaminopimelic acid, and N-acetyl-d-glucosamine (NAG) and DAP, which is unique in the cell walls of prokaryotic microorganisms. The teichoic and teichuronic acid are chemically bonded to peptidoglycan. Methods: One gram of soil samples was used to make suspension, by adding 99 mL of sterile distilled water (stock suspension) into it and shaking it in a shaker at 160 rpm for 30 minutes at room temperature. Serial dilutions from 0.1-0.001 were made from the stock suspension, and left for 10 minutes. After shaking, 0.1 mL of each dilution was cultured on Yeast Extract and Malt Extract agar (YEME) with Streptomycin 50 ug/mL. The inoculated plates were incubated at 28 °C for 7 to 10 days. Based on cultural characteristics, suspected colonies of Streptomyces were selected, which are characterized as small, white, pin-point, rough, chalky, and a clear zone of inhibition around them. These colonies were confirmed their identification by types of Gram’s stain, aerial and substrate mycelium color, pigment production, and pigment color.  Streptomyces were re-streaked on International Streptomyces project (ISP) to obtain pure colonies used for identification.   Results: The current study aimed to screen bacteria Streptomyces isolates. Only 21 samples of soil were suspected to contain Streptomyces, and 45 isolates were obtained with different morphology types per samples of soil. The colonies suspects were selected basis on color that ranged from gray, white and creamy. The microscopic examination of local Streptomyces spp. after Gram-staining method was conducted. The observations revealed that local Streptomyces is gram positive and rod shaped similar to features of fungal in possessing branched mycelium. The Streptomyces produced extra cellular enzymes like amylase, urease, catalase, protease, Gelatinase, cellulase and phosphatase. Utilization of citrate was positive, with no Melanine reaction production and soluble pigmented, and negative for indole production. Conclusion: The identification of the Streptomyces is a very complex process.  Morphological and biochemical characteristics are two important aspects for the classification in the Streptomycetaceae family. By studying the morphological, cultural, and biochemical characteristics, it is observed that the local isolates are belonging to the genus of Streptomyces.