The Journal of Cell Biology, Vol 102, 1209-1216, Copyright © 1986 by The Rockefeller University Press
Electrophysiological properties of Achlya hyphae: ionic currents studied by intracellular potential recording
DL Kropf
The electrical properties of the water mold Achlya bisexualis were
investigated using intracellular microelectrodes. Hyphae growing in a
defined medium maintained a membrane potential (Vm) of -150 to -170 mV,
interior negative. Under the conditions used here, this potential was
insensitive to changes in the inorganic ion composition of the medium.
Changes in external pH did affect Vm, but only outside the physiological pH
range. By contrast, the addition of respiratory inhibitors caused a rapid
depolarization without affecting the conductance of the plasma membrane.
Taken together these findings strongly suggest that the membrane potential
is governed by an electrogenic ion pump rather than by an ionic diffusion
potential. Previous work from this laboratory showed that Achlya hyphae
generate a transcellular proton current that enters the growing tip, flows
along the hyphal length, and exits distally from the trunk. These initial
experiments used an extracellular vibrating electrode, and I now report
intracellular electrical recordings which support the hypothesis that
protons enter the tip by symport with amino acids and are expelled distally
by a proton-translocating ATPase. Most significantly, current flowing
intracellularly along the hyphal length is associated with a cytoplasmic
electric field of 0.2 V/cm or greater. Conditions that inhibit the current
also abolish the internal field, suggesting that these two phenomena are
closely linked.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
