Differential Effects of Inhibitors on Respiratory Activity of Synchronous Cultures of Bacillus subtilis Prepared by Continuous-flow Centrifugation

Abstract

Size selection by continuous-flow centrifugation was used to prepare synchronous cultures of Bacillus subtilis. A selection of 5–10% was required to yield cultures which gave synchrony indices of about 0·45. Respiration rates [nmol O2 min−1 (ml culture)−1] of cells growing in the presence of glucose rose discontinuously as two steps in each cell cycle with the mid-points of the rises centred at 0·37 and 0·87 of a cycle. An asynchronous control culture exhibited no such periodicities. Two inhibitors of energy conservationN,N′-dicyclohexylcarbodi-imide and 4-chloro-7-nitrobenzofurazaninhibited respiration maximally at 0·0 and 0·6 of a cycle whilst an inhibitor of respiration2-heptyl-4-hydroxyquinoline-N-oxideexerted maximal effect only at 0·4 of a cycle. These results are compared with other temporal events which have been reported to occur during the cell cycle of B. subtilis.