Fungal control of early-stage bacterial community development in decomposing wood

Sarah R Christofides,Melanie Savoury,Lynne Boddy,Andrew J Weightman,Jennifer Hiscox

doi:10.1016/j.funeco.2019.100868

Abstract

The earliest stages of bacterial colonisation of wood have received little attention, particularly with respect to how the colonisation process may be affected by the presence of wood-decay fungi. This study used 16s rRNA gene sequencing to examine the bacterial community in wood that had been incubated in the field for 14 or 84 d, either in wood uncolonised by fungi or pre-colonised by Vuilleminia comedens, Trametes versicolor or Hypholoma fasciculare. All three fungal species significantly delayed bacterial colonisation of the wood. V. comedens and H. fasciculare also reduced bacterial OTU richness and altered bacterial community composition, increasing the relative abundance of Burkholderiales and reducing the proportion of Enterobacteriaceae and Bacteroidetes. Wood that had not been pre-colonised showed seasonal differences between autumn and spring: bacterial richness increased between 14 d and 84 d in the spring, but not in the autumn. Community composition at 84 d in spring was also different to the other time points, with reduced dominance of Gamma-proteobacteria. Archaea were also detected in nearly a third of samples, but with no apparent pattern, and always at low abundances.

Highlights

Decomposing wood is colonised by a mosaic of interacting fungal species that overall form a dynamic successional series, from the R and S species present during early decay, through a series of increasingly competitive decomposer species (Boddy, 2001)
The present study investigates the influence of fungal precolonisation and season on bacterial community composition in decomposing wood, during the earliest stages of colonisation
All the fungal pre-colonisers decreased the likelihood of bacterial presence, but T. versicolor had the largest negative effect, followed by H. fasciculare and V. comedens

Summary

Introduction

Decomposing wood is colonised by a mosaic of interacting fungal species that overall form a dynamic successional series, from the R (ruderal) and S (stress-tolerant) species present during early decay, through a series of increasingly competitive decomposer species (Boddy, 2001). At late stages of decay, these highly competitive fungi are in turn often replaced by stress-tolerant species. Bacteria are often said to be the earliest colonisers of wood, influencing which fungi can subsequently establish (Greaves, 1971; de Boer and van der Wal, 2008; Sun et al 2014), it is likely that bacteria colonising wood almost always encounter a fungal community that has already developed. There is evidence that wood-decay fungi exert active selection over bacteria, raising the possibility that fungi act as ‘gatekeepers’ determining which bacteria may enter a resource (Johnston et al 2018). The time-scales over which this operates are unknown (Johnston et al 2016)

Methods

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Discussion

Conclusion