Abstract
In Lake Shinji, Japan, periodic outbreaks of musty odour have occurred since mid-May 2007. Although the substance responsible for the odour was identified as geosmin, the odour-producing organism was unknown. We cultivated an axenic unialgal strain and determined that a species of Coelosphaerium (Synechococcales) was responsible for the production of geosmin in Lake Shinji. Our analysis was conducted using gas chromatography/mass spectrometry to determine the odorous compound. To determine the algae species, it was observed by optical microscopy to describe its morphological characteristics and the polymerase chain reaction was used to characterise the nucleotide sequence of the 16S rRNA gene and the 16S-23S rRNA internal transcribed spacer region. In addition, we explored the relationship between the number of cells of the Coelosphaerium sp. and the concentration of geosmin. In conclusion, geosmin, the cause of the musty odour in Lake Shinji in autumn 2009, was produced by Coelosphaerium sp., and to our knowledge, this is the first report of a geosmin-producing species in the family Coelosphaeriaceae.
Highlights
The first organisms that were confirmed to produce musty odour were actinomycetes
Assuming that Coelosphaerium species produce geosmin, we cultivated an axenic strain of Coelosphaerium species. We identified it using an optical microscope and polymerase chain reaction (PCR) analysis, measured geosmin by gas chromatography mass spectrometry (GC/MS), and checked that the number of Coelosphaerium sp. correlated with the concentration of geosmin
We suggested in our previous study that Coelosphaerium sp. produced the geosmin[11]
Summary
The first organisms that were confirmed to produce musty odour were actinomycetes. Many studies have reported that various cyanobacteria produce geosmin[6,7,8,9]. No odorous substance or odour-producing organism was identified[10]. The number of cells of Coelosphaerium kuetzingianum correlated with the concentration of geosmin in the separated portions of water samples. These result suggested that C. kuetzingianum produced geosmin. In the present study, we identified the organism only to the genus level because there are size differences in the colonies and the number of cells per colony between specimens from Europe and Lake Shinji (see taxonomic remarks in the Results section), suggesting that these may be different species
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