EFFECTS OF SEROTONIN (5-HYDROXYTRYPTAMINE) ON THE GROWTH AND DIFFERENTIATION OF MICROORGANISMS

Serotonin (5-hydroxytryptamine), a neurotransmitter and social behavio r factor in higher animals, accelerates culture growth and induces cel l aggregation in Escherichia coli and Rhodospirillum rubrum at concent rations of 2 x 10(-7)-2 x 10(-5) M. In the myxobacterium Polyangium sp ., 10(-6)-10(-5) M serotonin stimulates cell aggregation and myxospore formation. At concentrations over 20 mu M, serotonin induces the oppo site effect: it inhibits cell aggregation and microbial culture growth . Serotonin at these concentrations also inhibits light-dependent memb rane potential generation in Rsp. rubrum (the data were obtained by th e method of penetrating ions). Therefore, the above effects can be due to the elimination of the transmembrane electrical gradient by seroto nin. As for micromolar serotonin concentrations, their effects presuma bly result from the specific action of serotonin as an intercellular c ommunication agent accelerating and possibly synchronizing the develop ment of the cell population.