Control of flagellar motion in Chlamydomonas and Euglena by mechanical microinjection of Mg2+ and Ca2+ and by electric current injection.

Upon impalement with a microelectrode in a Ca-free medium containing 5 mM ATP, a Chlamydomonas cell lost its flagellar activity within 45 s, and the injection of either positive or negative direct current did not stimulate the flagella to beat after that time. When 3 mM Mg l + was added to the external medium, the impaled cell exhibited a flagellar frequency of 22 ± 7 Hz. With 5 mM ATP and 3 min Mg + in a Ca-free medium, negative direct electric current inhibited flagellar frequency and positive direct electric current enhanced flagellar activity. The flagella recovered to approximately their characteristic frequency (20 ± 6 Hz) upon the cessation of current. Euglena and Chlamydomonas cells were mechanically microinjected with Ca or Mg ions contained in 10 M KCl-filled microelectrodes. In both cells, the injection of C02 M Ca resulted in a decrease in flagellar frequency dependent on the amount of Ca + injected. The frequency decreased to zero Hz upon the injection of 16 x io~ 1. in Euglena and 3-5 x io~1. in Chlamydomonas. The microinjection of 10 x io~ 1. of 0-2 M Mg* into Euglena cells resulted in an approximately 2-fold increase in flagellar frequency. Chlamydomonas flagella, which stop beating upon impalement in a Mg-free medium, began to beat when the cell was injected with Mg+ ions. The flagella exhibited an average frequency of 16 ± 3 Hz when injected with 1-5 x io~1. of 0 2 M Mg. The data indicate that an increase in internal Mgstimulates flagellar frequency. The microinjection of Ca*+ inhibits flagellar motility.