Wood Inhabiting Bacteria

Freshly felled wood on the soil surface is rapidly colonized by bacteria (Clausen, 1996). The origin of these bacteria can be the tree itself (endophytes), air, rain water or soil. The early colonizing bacteria are thought to grow on easily degraded substrates like sugars, organic acids, pectin and easily accessed cellulose (Schmidt, 2006). However, there are also bacteria that degrade parts of the lignified cell wall. Based on microscopic observations two types of bacterial wood degradation have been observed namely tunnelling and erosion (Daniel, 2003). Both erosion and tunnelling bacteria probably degrade cellulose (Daniel, 2003). This is a very slow process, and the contribution of these bacteria to wood decay is minor when fungi are present as well (Daniel, 2003). However, under wet conditions they can, together with soft-rot fungi, be the major degraders of wood (Schmidt, 2006).

Actinomycetes can be considered to be the bacterial counterpart of fungi as most of them are hyphal organisms with good capabilities for degrading insoluble organic polymers, for example chitin and cellulose (Goodfellow and Williams, 1983). The importance of actinomycetes in the degradation of wood is, however, still unclear. Some actinomycetes can degrade lignin-model compounds, but the enzymes involved in lignin degradation still remain elusive (Kirby, 2006). A soil isolate of Streptomyces griseus did degrade only parts of the cellulose of wood powder, and solubilized only some of the lignin (Arora et al., 2005). If this is the general picture for actinomycetes then their contribution to decay of intact wood is probably minor.

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