Accumulation and Subcellular Localization of Cesium in Mycelia of Streptomyces lividans and a Cs Tolerant Strain, Streptomyces sp. TOHO-2.

Abstract

Cs uptake in Streptomyces lividans TK24 and Streptomyces sp. TOHO-2, as representatives of actinomycetes, was investigated. Growth of S. lividans TK24 was inhibited above 50 mM CsCl in yeast extract-malt extract agar, while that of Streptomyces sp. TOHO-2, which was isolated from soil as a Cs tolerant strain, was inhibited above 200 mM CsCl. The amount of Cs incorporated into the mycelia of these strains increased with the concentration of Cs in the medium; S. lividans TK24, grown in the presence of 25 mM Cs, accumulated 61.5 mgCs/g dry weight of mycelia, and Streptomyces sp. TOHO-2, grown in the presence of 150 mM Cs, accumulated 142.2 mgCs/g dry weight of mycelia. Scanning electron microscopy (SEM) of the substrate mycelia grown on the YM agar plate containing CsCl showed white spots with a similar distribution of mycelia. Elemental analysis using SEM-energy dispersive X-ray analysis showed that there were larger amounts of Cs, P and O in the brilliant spots than in other regions of the cell. Streptomyces lividans TK24 and Streptomyces sp. TOHO-2 could grow even in the presence of high concentrations of Cs, and accumulated high concentration of Cs in the cells.