[Radioactive cesium in total diet in Hokkaido (2011-2012)].

The level of radioactive cesium (the sum of (134)cesium (Cs) and (137)Cs) was investigated in total diet samples collected from adults living in the Sapporo area, Hokkaido. They were ashed, and examined with a germanium semiconductor detector. The maximum and average radioactivities of cesium in an indivividual's daily food intake were as follows: 1.0 Bq and 0.24 Bq in July 2011, 1.3 Bq and 0.30 Bq in November 2011, 3.9 Bq and 1.0 Bq in February 2012, and 0.34 Bq and 0.12 Bq in July 2012, respectively. The committed effective dose would be 0.022 mSv/year in the case of continued intake of meals containing the maximum cesium concentration.

H2O2 tolerance of Vibrio rumoiensis S-1(T) is attributable to the cellular catalase activity.

The extraordinarily high level of H2O2 tolerance of Vibrio rumoiensis strain S-1(T) when compared with the tolerance levels of strain S-4, a probable catalase-deficient derivative of strain S-1(T), was demonstrated by the introduction of 0-100 mM H2O2 during the mid-exponential growth phase. The contribution of catalase to the H2O2 tolerance was also demonstrated by comparing the catalase-deficient mutant Escherichia coli strain UM2 with a UM2 strain, harboring the plasmid pBSsa1, which carried the strain S-1(T) catalase gene vktA. The decomposition rates of 23-25 mM H2O2 that was introduced in the culture fluids of strain S-1(T) and E. coli UM2 harboring pBSsa1 corresponded to the calatase activities of the cells by spectrophotometric measurements. The presence of cell surface catalase was observed by immunoelectron microscopy, using an antibody for intracellular catalase in strain S-1(T). The high level of H2O2 tolerance of strain S-1(T) was attributable to the catalase activity of the cells. Cell surface catalase is considered to contribute to the catalase activity of strain S-1(T) cells.