Using Rhodopseudomonas palustris as a model bacterium to study fungal-bacterial interactions in wood decayed by the brown rot fungus Rhodonia placenta

Interactions between bacteria and fungi can be competitive or beneficial, but these relationships are not well understood because of a lack of good model systems. To model cross-feeding between fungi and bacteria, wood decayed by the brown rot fungus Rhodonia placenta was used as a carbon source for the phototrophic bacterium Rhodopseudomonas palustris.

We found that fungal decay products generated by Rda. placenta could be used by R. palustris for growth, and later decay stages contained more usable substrates than early stages. Mass spectrometry identified a range of aromatic and non-aromatic acids, but after 95 days of bacterial growth, R. palustris only consumed non-aromatic acids over the aromatic lignin monomers. Genes involved with aromatic compound degradation were unimportant for growth and RNA sequencing revealed that aromatic compound degradation genes were repressed on decayed wood extract.