Chemical investigations of the freshwater aquatic fungus Xylomyces chlamydosporus H58-1 have afforded a new radicinol derivative (1) and (2S, 3S)-3,7-dihydroxy-2,5-dimethyl-chroman- 4-one (2), along with the known radicinol derivatives 3-6, and radicinin derivatives 7 and 8. The structures of these metabolites were assigned by analysis of 1D and 2D NMR data.
The study of the fate of aflatoxin B1 (AFB1) in the rat demonstrated that the main site for the toxin absorption is the small intestine. AFB1 transferred from the intestinal lumen almost exclusively into the mesenteric blood. The increase in the rate of absorption nearly in proportion to the increase in AFB1 concentration in the medium suggests that AFB1 is absorbed substantially by passive diffusion. After being absorbed from the intestine, AFB1 enters exclusively into mesenteric vein and is partially converted to AFL by the blood cell. Comparison of the liver microsomal activity forming AFB1-DNA adduct among various species showed no correlation between the activity and species difference in susceptibility to AFB1 toxicity. However, a reverse relationship was observed between the liver cytosol glutathione-S transferase (GST) activity and species susceptibility, but no relationship was noted between the liver cytosol aldehyde reductase activity toward AFB1 aldehyde activity and species susceptibility. The results indicated the importance of liver cytosol GST activity in species differences in susceptibility to AFB1.
The influence of global warming on large area distribution of saprotrophic microfungi was considered. The research of the geographical distribution of fungi lags behind greatly compared with higher plants and animals because of some problems peculiar to the fungi. I proposed an investigation and a data analysis method to overthrowing the present situation. A process of investigating and analyzing the relation between the distribution pattern of a pine leaf litter fungus and the annual mean air temperature was described in detail. The result of curve fitting that used scatter charts showed that the distribution patterns of the species were able to be approximated by the quadratic function very well. This suggests that the geographical distribution of fungi is strongly influenced by macro-climate factors such as the annual mean air temperature or the seasonality. This distribution pattern was almost the same to the ordinal geographical distribution pattern of terrestrial plants. From this fact I presumed that almost all fungi have already started migrating north as global warming progresses, and that global warming will also cause serious problems for all creatures including human beings because the composition of present biological communities will be collapsed by the different responses of living things to temperature change. I also examined and discussed the problems to obstruct progress of the study of geographic distribution of the soil fungi from an ecological viewpoint.
LC/MS-MS method to analyse of Satratoxin G, Satratoxin H, Iso-satratoxin F and Roridin L2 and LC/TOF-MS method to analyse secondary metabolites including macrocyclic trichothecenes (MTRs) for the investigation of the production of MTRs and other secondary metabolites by Stachybotrys has been developed. Thirty-seven spores and nine hyphas of Stachybotrys were analysed. As a result, four MTRs were detected in nine spores and two hyphs and concentration of them ranged from 0.2 to 332.9 ng/106 in the spore and 3 to 784 ng/mL in the extract of hypha. Eleven MTRs, atranones, dolabellanes and stachybotrylactams and stachybocins were tentatively identified in the spore and the hypha. Extracted metabolites were filtered to thirty two metabolites for pathogenic characteristics such as haemolysis of red blood cell by multivariate statics. The abundance distribution of these metabolites of four spore extracts shown to induce haemolysis was very similar.
DNA double strand breaks are repaired through nonhomologous end joining (NHEJ) or homologous recombination (HR) in the eukaryotes from yeast to human. These systems have been applied for foreign DNA introduction into the host genome. In 2004, researchers discovered that inactivation of proteins involved in NHEJ leads highly efficient HR in a filamentous fungus Neurospora crassa. In a human pathogenic yeast Cryptococcus neoformans, NHEJ occurs quite often so that a large number of transformants should be determined before obtaining the genetically engineered strains with desired integration by HR. We disrupted genes coding for DNA ligase IV or so called KU proteins, which are responsible for NHEJ in C. neoformans. The strains were indistinguishable in growth and other phenotypes, but the HR efficiencies were elevated.
Ultrastructure of cells has been examined by many studies including electron microscopy, leading to an impression that full knowledge about the cell has already been attained. However, quantitative and three-dimensional information are still lacking; the number of ribosomes per cell and numbers and cellular distribution of endoplasmic reticulum are not yet known. I have introduced a new concept “structome”, coined from the combination of structure and -ome, and defined as “information on the quantitative and three-dimensional structure of whole cells at electron microscopic level.” In the present study, structome analysis has been undertaken in yeast Exophiala dermatitidis using freezesubstitution and serial ultrathin sectioning. It was found that there were ~200,000 ribosomes in a cell;17-52 mitochondria in a cell and occupied ~10 % of the cell volume; and 5 - 10 endoplasmic reticula and occupied only ~ 0.2 % of the cell volume.
Recently FAO/WHO JECFA (Joint FAO/WHO Expert Committee on Food Additives) and EFSA (European Food Safety Authority) have evaluated the risk assessment for mycotoxins. In 2008, Codex Alimentarius Commission has set the maximum residues limits (MRL) of total aflatoxins in processed and ready to eat tree nut. Responding to Codex regulation, Food Safety Commission (FSC) in Japan has evaluated the risk assessment of total aflatoxins in food. Based on the report from FSC, Ministry of Health, Labour and Welfare moves into action to establish the MRL for total aflatoxins in peanut and tree nut. I introduce the report from FSC the risk assessment of total aflatoxins in food and the process of setting MRL.
The Codex Alimentarius Commission (CAC) as an international body laying down standards has been establishing maximum levels for some mycotoxins in foods. In 2008, the CAC has set the maximum levels for total aflatoxins in processed and ready-to-eat tree nuts. By responding to the CAC action, the Ministry of Health, Labor and Welfare in Japan moves into action to set the maximum levels for total aflatoxins in peanuts and tree nuts. Under these circumstances, the Consultation for Evaluation of Methods for Mycotoxins Analysis in Japan has validated the method of analysis for total aflatoxins in peanuts and tree nuts. Based on the validated method, the Committee made out a draft of the method of analysis for total aflatoxins in peanuts and tree nuts.