Characterization of the antibiotic compound no. 70 produced by Streptomyces sp. IMV-70

Characterizationharacterization of Extremophilic Actinomycetes Strains as Sources of Antimicrobial Agents

Extremophilic actinomycetes strains can survive extreme saline and alkaline environments and produce antimicrobial agents. In this chapter, we discuss laboratory methods that can be used to isolate and characterize actinomycetes strains capable of potentially producing novel antimicrobial agent(s) when cultured in conditions that mimic the environments from which they were isolated. Methods used to screen for antibacterial and antiviral activities from these producer strains, and microbiological and molecular approaches used to identify these strains are described. Here we describe three methods. Method 1 focuses on the strategy to select optimal conditions to synthesize and accumulate the antibiotics from the studied actinomycetes strains by preparing crude extracts. In Method 2, we describe the screening strategies used to test the actinomycetes strains against gram-negative and gram-positive bacteria, antifungal agents, multidrug-resistant pathogens (MDR), and viral pathogens. Thus, the specific techniques to test for MDR pathogens such as the disk diffusion assay and wells assay are outlined. We also describe the antiviral activity screening of the selected actinomycetes extracts in Method 2 of this chapter. Specifically, we concentrate on methods used to test for antiviral activities such as primary hemolytic, hemagglutination, neuraminidase, and specific virus-inhibitory activities. Finally, the Method 3 section reveals the microbiological techniques used to morphologically characterize the actinomycetes strains that depend on the culture medium utilized for growth. Additionally, the method used to perform a detailed characterization of the morphology that actinomycetes strains possess is specified by the protocol for sample preparation and visualization using the scanning electron microscopy (SEM). Finally, we summarize the molecular approaches used to characterize actinomycetes strains, focusing specifically on the PCR and sequencing techniques.

Antibacterial and Antifungal Activity of Novel Freshwater Bacterium Tabrizicola aquatica as a Prominent Natural Antibiotic Available in Qurugol Lake

Background : Recently, resistant pathogenic microorganisms have become increasingly wide spread. The search for new natural antibiotics is a viable solution to this problem. For this aim we investigated the antimicrobial ability of Tabrizicola aquatica, the novel bacterium isolated from Qurugol Lake located nearby Tabriz city, Iran. Methods: The antimicrobial properties of Tabrizacola aquatica was investigated using well diffusion test. Tabtizicola aquatica was incubated at 40℃ in shaking incubator at 150 rpm for 14 days. The culture was centrifuged to obtain cell free supernatant, which was sterilized using 0.2 μm filter paper and lyophilized. Microorganisms were lawn and then wells were prepared over the agar plates. About 100 ml of the diluted lyophilized supernatant was added to the wells. The plates then were incubated at 37℃. After 48 hours, antimicrobial activity was defined by measuring the inhibition zone diameter. Results: The bacterial filtrates had considerable antagonistic effect against Escherichia coli, Rhizobium radiobacter, Pseudomonas syringae, Erwinia amylovora, Botrytis cinerea, Neurospora crassa and Fusarium oxysporum. However, the filtrates did not show any inhibitory action on the Aspergillus flavus and Klebsiella pneumonia. The supernatant decreased the growth zone on Streptococcus aureus, Pseudomonas aeruginosa, Shigella flexneri, Xanthomonas camoestris and Bassilus cereos. The result of MIC against pathogens was found for Neurospora crassa in the 50 µg/mL. Conclusion: The results, suggested that Tabrizicola aquatica and similar bacteria can be helpful to control freshwater natural water sources from pathogenic microorganism. Moreover, microbial natural products are still the most promising source of new antibiotics. Our results point out a scope for characterization of the metabolites and could be a candidate in the identification of novel antibiotics.

Successive nonstatistical and statistical approaches for the improved antibiotic activity of rare actinomycete Nonomuraea sp. JAJ18

The selection and optimization of nutritional constituents as well as their levels for the improved production of antibiotic by Nonomuraea sp. JAJ18 were carried out using combination of both nonstatistical one-factor-at-a-time (OFAT) method and statistical response surface methodology (RSM). Using OFAT method, starch and (NH4)2SO4 were identified as suitable carbon and nitrogen sources, respectively. Subsequently, starch, NaCl, and MgSO4 · 7H2O were recognized as the most significant media components with confidence level of above 95% using the Plackett-Burman design. The levels of the three media components were further optimized using RSM employed with Box-Behnken design. Accordingly, a second-order polynomial regression model was fitted into the experimental data. By analyzing the response surface plots as well as using numerical optimization method, the optimal levels for starch, NaCl, and MgSO4 · 7H2O were determined as 15.6 g/L, 0.8 g/L, and 1.98 g/L, respectively. With the optimized medium, 15.5% increase was observed in antibiotic activity of JAJ18. Results further support the use of RSM for media optimization. To the best of our knowledge, this is the first report of statistical media optimization for antibiotic production in rare actinomycete Nonomuraea species, which will be useful for the development of Nonomuraea cultivation process for efficient antibiotic production on a large scale.