The transcriptome response of the ruminal methanogen Methanobrevibacter ruminantium strain M1 to the inhibitor lauric...

Lauric acid (C₁₂) is a medium-chain fatty acid that inhibits growth and production of the greenhouse gas methane by rumen methanogens such as Methanobrevibacter ruminantium. To understand the inhibitory mechanism of C₁₂, a transcriptome analysis was performed in M. ruminantium strain M1 (DSM 1093) using RNA-Seq.

Pure cell cultures in the exponential growth phase were treated with 0.4 mg/ml C₁₂, dissolved in dimethyl sulfoxide (DMSO), for 1 h and transcriptomic changes were compared to DMSO-only treated cells (final DMSO concentration 0.2%). Exposure to C₁₂ resulted in differential expression of 163 of the 2280 genes in the M1 genome (maximum log₂-fold change 6.6). Remarkably, C₁₂ hardly affected the expression of genes involved in methanogenesis. Instead, most affected genes encode cell-surface associated proteins (adhesion-like proteins, membrane-associated transporters and hydrogenases), and proteins involved in detoxification or DNA-repair processes. Enrichment analysis on the genes regulated in the C₁₂-treated group showed a significant enrichment for categories 'cell surface' and 'mobile elements' (activated by C₁₂), and for the categories 'regulation' and 'protein fate' (represssed). These results are useful to generate and test specific hypotheses on the mechanism how C₁₂ affects rumen methanogens.