SOME EFFECTS OF UNCOUPLERS AND INHIBITORS ON GROWTH AND ELECTRON-TRANSPORT IN RUMEN BACTERIA

Uncouplers and inhibitors of electron transport affected growth and electron transport of rumen bacteria in various ways. Selenomonas ruminantium was not affected by inhibitor and uncoupler concentrations which affected growth and electron transport of Bacteroides ruminicola, B. succinogenes and Butyrivibrio fibrisolvens. Inhibitors, when active, led to accumulation of reduced electron carriers before the site of action, but differences were found among organisms in the site of action of these inhibitors. Uncouplers reduced the glucose molar growth yields (Ygluc) of B. ruminicola, B. succinogenes and B. fibrisolvens compared with those obtained without uncouplers. The extent of Ygluc reduction accompanying inhibitor exposure reflected electron transport chain structure. S. ruminantium appeared to obtain its ATP from substrate-level processes only. The other organisms studied appeared to obtain ATP both from substrate-level processes and from electron transport, but differed in the amount of ATP obtained from glucose catabolism and in the proportions of ATP obtained from substrate-level reactions and electron transport.