Coordinated lignin degradation by various bacteria in nature

This study describes the microbiome of the decayed wood in the natural forest. Bacteria have been shown to decompose lignin in vitro, their lignin-decomposing activity has not been demonstrated in nature. Hence, this study aimed to identify the bacterial communities involved in lignin degradation and functional profile of bacterial lignin degradation in wood decayed by white-rot fungi using microbial community analyses. The flora of forest soil and decayed wood were drastically different, with Sphingomonas, Methylobacterium, and Acidibrevibacterium being more abundant in decayed wood than in forest soil. Furthermore, bacteria that degrade the major skeleton of lignin in vitro, such as sphingomonads, were present in decayed wood. Thus, multiple bacteria coordinately function to degrade lignin; the mechanism is suggested as follows: solid lignin is first degraded by white-rot fungi, the resultant low-molecular-weight lignin is kept uncondensed by formaldehyde produced by Methylobacterium sp., and then the uncondensed lignin is degraded by bacteria such as sphingomonads, whose role in the lignin degradation has been reported previously. This is the first report for clarifying the lignin degradation process of the decayed wood in the natural forest.