A novel actinomycete Streptomyces aurantiogriseus with algicidal activity against the toxic cyanobacterium Microcystis a
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A novel actinomycete Streptomyces aurantiogriseus with algicidal activity against the toxic cyanobacterium Microcystis aeruginosa Theerasak Somdee & Nopmanee Sumalai & Anchana Somdee
Received: 24 November 2012 / Revised and accepted: 29 January 2013 # Springer Science+Business Media Dordrecht 2013
Abstract A novel actinomycete strain (PK1) was isolated from soil in Khon Kaen Province, Thailand, and was capable of inhibiting the cyanobacterium Microcystis aeruginosa. The isolate PK1 was identified as Streptomyces aurantiogriseus based on an analysis of biochemical and morphological characteristics and 16S rDNA sequence. The algicidal activity of PK1 against M. aeruginosa depended on the growth phase of PK1, but not on the cyanobacterial growth phase. Stationary growth phase cultures of the strain PK1 exhibited the highest anti-Microcystis activity when co-cultivated with M. aeruginosa. Complete growth inhibition was observed after 8 days of co-cultivation in liquid culture medium. The algicidal compounds were extracted from PK1 with ethyl acetate and then purified by silica gel column chromatography. These partially purified compounds demonstrated algicidal activity against M. aeruginosa, suggesting that the strain PK1 provides a potential source of extracellular compounds for the control of M. aeruginosa bloom. This is the first report of anti-cyanobacterial activity from the soil actinomycete S. aurantiogriseus. Keywords Streptomyces aurantiogriseus . Microcystis aeruginosa . anti-Microcystis . actinomycetes
Introduction Blooms of cyanobacteria (blue green algae) are widespread in bodies of water located throughout the world. These blooms T. Somdee (*) : N. Sumalai : A. Somdee Department of Microbiology, Faculty of Science, Khon Kaen University, Khon Kaen 40000, Thailand e-mail: [email protected]
pose a serious health threat to animals and humans because some cyanobacteria genera produce toxic secondary metabolites known as cyanotoxins (Sivonen and Jones 1999). The most frequently reported toxic bloom-forming cyanobacterium found in freshwater belongs to the genus Microcystis and is capable of producing cyclic peptide hepatotoxins called microcystins. Several processes have been reported to date for the elimination of Microcystis blooms from lakes and reservoirs, e.g., manual removal of the bloom using boats or killing of cyanobacteria by chemical algicides such as copper sulfate or altering fish and zooplankton food webs (McGuire et al. 1984). However, none of these processes have been successfully implemented due to the high treatment costs and secondary pollution, which are two major obstacles to their general use. Therefore, research on more economical and environmentally acceptable methods for the control of Microcystis bloom is still needed. Recently, many studies with these goals have focused on the use of biological agents, especially algicidal bacteria, which have been reported to exhibit valid control of the bloom of harmful algae in marine and freshwater environments. Several strains of algicidal bac
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