Antagonistic Properties of Some Halophilic Thermoactinomycetes Isolated from Superficial Sediment of a Solar Saltern and Production of Cyclic Antimicrobial Peptides by the Novel Isolate Paludifilum halophilum.

Donyez Frikha Dammak,Mostafa E Rateb,Rayed Abdennabi,Ziad Zarai,Lassaad Belbahri,Sami Maalej,Soumaya Najah,Hafedh Mejdoub

doi:10.1155/2017/1205258

Abstract

This study has focused on the isolation of twenty-three halophilic actinomycetes from two ponds of different salinity and the evaluation of their ability to exert an antimicrobial activity against both their competitors and several other pathogens. From the 23 isolates, 18 strains showed antagonistic activity, while 19 showed activities against one or more of the seven pathogen strains tested. Six strains exhibited consistent antibacterial activity against Gram-negative and Gram-positive pathogens characterized at the physiological and molecular levels. These strains shared only 94-95% 16S rRNA sequence identity with the closely related species of the Thermoactinomycetaceae family. Among them, the potent strain SMBg3 was further characterized and assigned to a new genus in the family for which the name Paludifilum halophilum (DSM 102817T) is proposed. Sequential extraction of the antimicrobial compounds with ethyl acetate revealed that the crude extract from SMBg3 strain had inhibitory effect on the growth of the plant pathogen Agrobacterium tumefaciens and the human pathogens Staphylococcus aureus, Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa. Based on the HRESI-MS spectral data, the cyclic lipopeptide Gramicidin S and four cyclic dipeptides (CDPs) named cyclo(L-4-OH-Pro-L-Leu), cyclo(L-Tyr-L-Pro), cyclo(L-Phe-L-Pro), and cyclo(L-Leu-L-Pro) were detected in the fermentation broth of Paludifilum halophilum. To our knowledge, this is the first report on the isolation of these compounds from members of the Thermoactinomycetaceae family.

Highlights

Actinomycetes are considered as an intermediate group of bacteria and fungi and recognized as prokaryotic organisms
Considering the rising need of new antibiotics to combat the emergence of drug-resistant bacteria, many microbiologists have focused their recent research on actinomycetes from nonconventional environments where particular chemical and physical factors contribute to the selection of species that are best adapted to BioMed Research International that extreme environment
This study deals with the isolation, characterization, and antimicrobial potentiality of a collection of halophilic actinomycete strains isolated from the solar saltern of Sfax

Summary

Introduction

Actinomycetes are considered as an intermediate group of bacteria and fungi and recognized as prokaryotic organisms. Considering the rising need of new antibiotics to combat the emergence of drug-resistant bacteria, many microbiologists have focused their recent research on actinomycetes from nonconventional environments where particular chemical and physical factors contribute to the selection of species that are best adapted to BioMed Research International that extreme environment. To cope with their environmental stressful factors, these microorganisms have developed a complex stress management for their survival, which is being unrevealed for multiple purposes [5, 6]. Groups of acidophilic and alkaliphilic, psychrophilic and thermophilic, halophilic and haloalkaliphilic, and xerophilic actinomycetes have been described [7, 8]

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Conclusion