ABSTRACT
BACKGROUND: Stable cesium (133Cs) naturally exists in the environment whereas recently deposited radionuclides (e.g., 137Cs) are not at equilibrium. Stable cesium has been used to understand the long-term behavior of radionuclides in plants, trees and mushrooms. We are interested in using 133Cs to predict the future transfer factor (TF) of radiocesium from contaminated logs to shiitake mushrooms in Eastern Japan. However, the current methodology to obtain a representative wood sample for 133Cs analysis involves mechanically breaking and milling the entire log (excluding bark) to a powder prior to analysis. In the current study, we investigated if sawdust obtained from cutting a log along its length at eight points is as robust but a faster alternative to provide a representative wood sample to determine the TF of 133Cs between logs and shiitake. METHODS: Oak logs with ready-to-harvest shiitake fruiting bodies were cut into nine 10-cm discs and each disc was separated into bark, sapwood and heartwood and the concentration of 133Cs was measured in the bark, sapwood, heartwood, sawdust (generated from cutting each disc) and fruiting bodies (collected separately from each disc), and the wood-to-shiitake TF was calculated. RESULTS: We found that the sawdust-to-shiitake TF of 133Cs did not differ (P = 0.223) compared to either the sapwood-to-shiitake TF or heartwood-to-shiitake TF, but bark did have a higher concentration of 133Cs (P < 0.05) compared to sapwood and heartwood. Stable cesium concentration in sawdust and fruiting bodies collected along the length of the logs did not differ (P > 0.05). DISCUSSION: Sawdust can be used as an alternative to determine the log-to-shiitake TF of 133Cs. To satisfy the goals of different studies and professionals, we have described two sampling methodologies (Methods I and II) in this paper. In Method I, a composite of eight sawdust samples collected from a log can be used to provide a representative whole-log sample (i.e., wood and bark), whereas Method II allows for the simultaneous sampling of two sets of sawdust samples-one set representing the whole log and the other representing wood only. Both methodologies can greatly reduce the time required for sample collection and preparation.
ABSTRACT
Several functional genes encoding putative proteins, heat shock protein 70, sphingosine phosphate lyase, and Na+/H+ antiporter, were cloned from the basidiomycete Fomitopsis pinicola, a wood-rotting fungus isolated in the tropical mangrove forest of Pohnpei Island of the Federated States of Micronesia. The deduced amino acid sequences of the obtained genes involved in heat shock resistance, lipid synthesis, and salt tolerance showed diverse similarities to other homologous proteins. Molecular phylogenetic trees of these proteins suggested that encoded proteins of the cloned genes of F. pinicola differed remarkably from other homologs in various organisms, even fungal proteins. Putative candidates for other genes related to several cellular metabolisms were also amplified, implying the possible existence of those genes in F. pinicola. This is the first report of possibly functional genes derived from a basidiomycetous mushroom growing in tropical islands such as Micronesia. The genes found in this study might play important roles in the cellular survival of the basidiomycete F. pinicola under severe environmental conditions.