Transcriptome of the biofilm forming cocultures of Syntrophobacter fumaroxidans and hydrogenotrophic methanogens. Deciphering the mechanisms of biofilm formation in the propionate-oxidizing methanogenic cocultures

The objectives of this study were to examine biochemical changes associated with cell aggregation in cocultures of syntrophic propionate oxidizing Syntrophobacter fumaroxidans and hydrogenotrophic methanogens, Methanospirillum hungatei or Methanobacterium formicicum. To observe and study the formation of methanogenic aggregates, cocultures of syntroph and methanogens were maintained for a year in a fed-batch growth mode. Choice of the hydrogenotrophic methanogen influenced the morphology of the millimeter-scale coculture aggregates, which were observed within the 5 months of the cultivation. Aggregates of S.fumaroxidans and M.formicicum had 2x faster substrate/product turnover rates, compared to the dispersed cocultures. Differential expression analysis of the transcriptome from dispersed and aggregated cocultures points to statistically significantly higher expression of genes for signal transduction, polysaccharide secretion and metal transporters in the aggregated cocultures, compared to the dispersed ones.