Physiological responses of Bacillus species to concanavalin A. 2. Effect on growth, oxygen uptake, enzyme activities and intracellular cyclic guanosine 3',5'-monophosphate level of B. cereus ATCC 14579.

The effect of the mitogen concanavalin A (Con A) on growth and several physiological aspects of Bacillus cereus ATCC 14579 was investigated. Con A at concentrations ranging from 50 to 750 micrograms/ml stimulated growth (the growth rate increased from 0.52/h to 0.97/h, and final yield increased by 2.3-fold over the control) of the bacterial cells. Con A-treated cells also increased their oxygen uptake (1.6-fold increase when treated with 750 micrograms/ml of Con A). The activities of the membrane-bound dehydrogenase and phosphatase increased by 1.75-fold and 2.1-fold, respectively, when treated with 500 micrograms/ml of Con A. However, only a one-fold increase in alpha-glucosidase activity was observed when cells were treated with the same concentration of Con A. Con A at concentrations of 500 to 1,000 micrograms/ml stimulated the cellular synthesis of cyclic guanosine 3',5'-monophosphate (cGMP) by one-fold. It is proposed that binding of Con A to the cell envelope led to increased synthesis of cGMP which might serve as an intracellular messenger for expression of the mitogenic signal of Con A. Since the use of 50 mg/ml of alpha-methyl-D-mannopyranoside (alpha-MM), a Con A inhibitor, could reverse the stimulatory effect of Con A, it was obvious that the stimulatory action was initiated by the specific binding of Con A molecules to the cell envelope. Furthermore, the stimulatory effect was found to be Con A dosage dependent.