Intracellular Microstructural Observation of Musty Odor Producing Filamentous Cyanobacteria, Phormidium tenue, Comparative Observations Using Soft X-ray Microscope, Transmission Electron Microscope, and Low Temperature/Low Vacuum Scanning Electron Microscope

Abstract

One of the causative substances of musty odors which have frequently occurred in Lake Biwa were identified as 2-methylisoborneol (MIB), and the causative organisms were identified as Phormidium tenue. Musty odor producing and non-producing Phormidium tenue were observed with a soft x-ray microscope (XM), a transmission electron microscope (TEM), and a low temperature/low vacuum scanning electron microscope (low temperature/low vacuum SEM). While MIB producing strain (green strain) was composed of thick cells without mucilaginous sheath, MIB non-producing strain (brown strain) was composed of slender cells with mucilaginous sheath. Although carboxysomes and polyphosphate granules were observed in both green and brown strains, the polyphosphate granules were larger than the carboxysomes in green strain. Morphological differences between the green and the brown strains suggest a possibility that the green and the brown strains are different species. The experimental results lead to the conclusion that it is possible to distinguish musty odor producing and non-producing strain based on the morphological feature using XM, TEM, and low temperature/low vacuum SEM.