Revealing colonisation and biofilm formation of an adherent coal seam associated microbial community on a coal surface

•A method is presented to visualise microbial communities growing on coal surfaces.•Distinct successional changes were seen in the microbial community over time.•Biofilms were observed to form on coal surfaces over time.

The discovery that coal seam microbial communities contribute appreciably to coal seam methane (CSM) reserves worldwide has led to an increased interest in the coal seam microbiome. While studies to date have focussed on characterising the microbial communities in a mature state, very little has been reported on the physical niche partitioning and colonisation processes of these communities on coal surfaces. Coal represents a difficult substrate for microbial characterisation using classical techniques due to in its adsorptive nature and recalcitrance to reflectance and fluorescence-based microscopy. This study presents a new technique involving culturing on specially prepared polished coal disks which allows for examination of microbes adherent to the coal surface using both molecular and microscopic approaches. Using this technique we have investigated the colonisation process of the coal surface including evidence for the involvement of a biofilm and successional changes in abundance of several community members during colonisation.