Antibacterial potential of streptomycete strains from Antarctic soils

Marta Encheva-Malinova,Mariya Stoyanova,Hristina Avramova,Yanitsa Pavlova,Blagovesta Gocheva,Iskra Ivanova,Penka Moncheva

doi:10.1080/13102818.2014.947066

Abstract

The exploration of habitats with unusual environment and poorly explored areas such as Antarctica is one of the strategies for discovery of new biologically active substances and/or new producers. The aim of this study was to identify the actinomycetes isolated from the soils of the island Livingston – Antarctica and to investigate their potential to synthesize antibacterial agents against phytopathogens. Twenty-three actinomycete strains were the object of this study. Using PCR (polymerase chain reaction) amplification all strains were affiliated to genus Streptomyces.The sequencing of the 16S rRNA for three of the strains showed greatest similarity to Streptomyces tendae for one of them, and revealed that the other strains had closest relations to streptomycetes isolated from anthropogenically unaltered regions including Antarctica.The isolates were studied for production of antibacterial substances both by molecular and culture methods. PCR targeting specific biosynthetic genes involved in the production of some groups of antibiotics was performed. The screening showed that all strains possessed the gene for Type-II polyketide synthase, 11 strains – for non-ribosomal peptide synthetase; 6 strains – for polyene antibiotics; and 4 strains – for glycopeptide antibiotics. The production of antibacterial substances by the strains was tested in vitro against phytopathogenic bacteria. The strains differed in the number of inhibited test – bacteria and in their spectrum of action. Four strains showed a wide range of activity against Gram-positive and Gram-negative phytopathogens.The results obtained revealed that the Antarctic soils are potential source for isolation of streptomycetes producing antibiotics from different groups.

Highlights

Antarctica is the southernmost continent and is surrounded by the southern waters of the World Ocean
Streptomycetes are Gram-positive, filamentous typical soil bacteria with high content of G C C and belong to the group of the actinomycetes which are relatively less investigated as a component of microbial communities in Antarctica, but there are studies that demonstrate their ability to synthesize biologically active substances of different nature.[1À8] The genus Streptomyces is composed of a large number of species many of which synthesize a broad spectrum of secondary metabolites
This study aims to identify actinomycete strains isolated from soils of Livingston Island, Antarctica, and to investigate their potential to synthesize antibacterial agents against phytopathogenic bacteria

Summary

Introduction

Antarctica is the southernmost continent and is surrounded by the southern waters of the World Ocean. It is the coldest, driest and windiest continent; approximately 98% of it is covered by ice. Despite the harsh and unique environmental conditions, a greater than expected organism diversity was found À including a number of endemic and yet unknown species. Streptomycetes are Gram-positive, filamentous typical soil bacteria with high content of G C C and belong to the group of the actinomycetes which are relatively less investigated as a component of microbial communities in Antarctica, but there are studies that demonstrate their ability to synthesize biologically active substances of different nature.[1À8] The genus Streptomyces is composed of a large number of species many of which synthesize a broad spectrum of secondary metabolites. Several studies have been focused on identifying biocontrol agents which could be used as an alternative to agrochemicals in plant protection.[9]

Objectives

Methods

Results