Microbiological community structure on logs used for groynes in a riverbank system

Abstract

Abstract It is important for civil engineering applications to investigate resistance to wood decay in aqueous environments. DNA from microorganisms inhabiting logs (groynes) that had been used for about 15 years as a water control system to prevent riverbank erosion was extracted and the microbial community structure was examined. DNA was extracted from specimens in four sections, above and under the water, under the ground and from the bottom parts of the logs that were pulled out from the river. Then, barcode sequences for the detection of fungi and bacteria were amplified from each DNA sample by polymerase chain reaction. Microbes were identified from the nucleotide sequences, and the relationships between microbes and environmental conditions were discussed. The wood in the section above the water was significantly decayed, while slight decay and strength loss were observed in the other sections. The white-rot basidiomycete Xeromphalina sp. was detected in the section above the water, suggesting that this fungal species was responsible for the significant decay of the logs in this study. Wood in the sections under the water and under the ground including the bottom of the logs was not decayed even though the fungus was detected in all sections of the logs, suggesting that Xeromphalina sp. could not degrade the wood in the water and underground where the oxygen supply was limited.

Keywords

• Groyne
• Water system log
• Wood-rot fungi
• Bacteria
• Wood decay