Effect of gramicidin on methanogenesis by various methanogenic bacteria.

Methanogenesis by Methanobacterium thermoautotrophicum strains was extremely sensitive to gramicidin, total inhibition being observed at 0.2 mug/ml. In contrast, methane synthesis by Methanococcus voltae, Methanogenium marisnigri, Methanosarcina mazei, and Methanospirillum hungatei were resistant to the highest concentrations of gramicidin tested (40 mug/ml), although spheroplasts of Methanospirillum hungatei were extremely sensitive. Other species tested showed intermediate sensitivity to gramicidin, methanogenesis inhibition occurring at 4 to 20 mug/ml.