Abstract
The “Sebkha of Monastir” is a Tunisian permanent wetland that constitutes a virgin environment to search new biotechnologically relevant microorganisms and activities. A total of 71 different strains were isolated, including 54 Streptomyces, 2 Micromonospora, 2 Nocardia, 4 Pseudonocardia and 9 non-streptomyces actinomyetes. Interesting antimicrobial activities were detected in liquid and solid cultures. The antimicrobial profiles depended upon the culture medium and/or the organic extraction. Several bioactive compounds were identified by liquid chromatography (LC) combined with mass spectrometry (MS) and then analyzed by MEDINA´s database and the Dictionary of Natural Products Chapman & Hall. Isoflavones (genistein and deidzein) are the most produced known active compounds. The chemical structures of four putative novel compounds were elucidated. Interestingly, unknown compounds produced by two strains (A8 and A11) actives against Gram negative bacteria were selected for further analysis on a large-scale. 16S rDNA sequencing allowed us to classify some active isolates as members of the Streptomyces and Micromonospora genera. All these findings prove the high antimicrobial activity of the actinomycetes strains isolated from the “Sebkha of Monastir”. The potential of this and other relatively unexplored extreme environments constitute a source of new biologically active secondary metabolites.
Highlights
The search for novel antibiotics becomes paramount to counter the development of resistant pathogens, the evolution of new diseases and the toxicity of some of the current compounds [1]
For different genera were detected. It approve that low taxonomic biodiversity is observed in all most the saline environments around the world (the Great Salt Lake (Utah, USA), the alkaline brines of WadiNatrun (Egypt) and Lake Magadi (Kenya)) [22]
Several factors can affect the antimicrobial potential of the actinomycetes strains
Summary
The search for novel antibiotics becomes paramount to counter the development of resistant pathogens, the evolution of new diseases and the toxicity of some of the current compounds [1]. Significant advancement is being made in chemical synthesis and engineered biosynthesis of biomolecules, nature remains the richest and the most versatile source for new antimicrobial compounds [2]. The environment can affect microbial metabolism antibiotics producing microorganisms have been isolated from unusual habitats [6]. Extremophilic actinomycetes are the most promising source for antimicrobial compounds due to their unique and diverse community structure and various unexplored metabolic pathways [8]. Despite these findings, little is known about the diversity of actinomycetes in saline environments which constitute an uncommon extreme ecosystem [9]
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