Bioactivity of endophytic bacteria and yeasts isolated from Thymus

Abstract

Endophytes are important resources of bioactive compounds and due to their potential in theproduction of secondary metabolites, they are regarded as a potential reservoir ofbiotechnological applications. In this study, the bioactivity of bacteria and yeasts endophytesresiding in Thymus sp. was evaluated. During April to October 2011, symptomless and healthytissues of Thymus sp. were collected. A total of 23 strains of endophytic bacteria and 6 yeastswere isolated. The bio-effects of the endophytes were studied on Botrytis cinerea and plantpathogenic bacteria Xanthomonas arboricola pv. juglandis and Streptomyces scabies andhuman pathogens Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC. Growthinhibition mechanisms of the endophytes against B. cinerea were evaluated and it seems that theantimicrobial effects of bacterial endophytes are related to the production of protease enzyme,hydrogen cyanide and volatile compounds. Bacterial strains were identified as Bacillus,Pseudomonas and Xanthomonas of which Bacillus was the predominant isolate. For the firsttime, Bacillus is reported from Thymus eriocalyx, T. lancifolius, T. fallax, T. kotschyanus and T.vulgaris and Pseudomonas and Xanthomonas as endophytic bacteria from Thymus.