The influence of K+ ions on the components of the transmembrane proton motive force (delta mu H+) in intact bacteria was investigated. In K+-depleted cells of the glycolytic bacterium STreptococcus faecalis the addition of K+ ions caused a depolarization of the membrane by about 60 mV. However, since the depolarization was compensated for by an increase in the transmembrane pH gradient (delta pH), the total proton motive force remained almost constant at about 120 mV. Half-maximal changes in the potential were observed at K+ concentrations at which the cells accumulated K+ ions extensively. In EDTA-treated, K+-depleted cells of Escherichia coli K-12, the addition of K+ ions to the medium caused similar, although smaller changes in the components of delta mu H+. Experiments with various E. coli K-12 K+ transport mutants showed that for the observed potential changes the cells required either a functional TrkA or Kdp K+ transport system. These data are interpreted to mean that the inward movement of K+ ions via each of these bacterial transport systems is electrogenic. Consequently, it leads to a depolarization of the membrane, which in its turn allows the cell to pump more protons into the medium.

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Sinohesione genituliphoru gcn. ct sp. n. (Polychaeta. Hcsionidac), an intcrstitial annclid with unique dimorphous external genital organs.-Zool. Scr. 23: 95-105.A ncw hcsionid. Sinohesione genitaliphora gcn. ct sp. n.. is dcscribcd from intertidal sandy sediments of Hainan Island, China. It diffcrs from hithcrto known hcsionids by the prcscncc of cxtcrnal genital organs in both sexes. In the malcs thcrc is onc pair of sac-like appendages, cach bearing a tubc-shapcd pcnis, o n chaetigcr 10. In thc fcmalcs thc paircd sac-shepcd orgins arc situated on chaetigcr 12. Reconstructions of scmi-and ultrathin scctions show that ii long, hciivily coilcd spcrm duct opcns at the tip of each pcnis. Thc duct opcns with a ciliated funnel into ii seminal vesicle in chactigcr 9. Prominent gland cclls surround thc spcrm duct for the most part. 'I'hc female genital organs cach havc two opcnings; one of which lcads t o a blind cnding scmin;il rcccptaclc. The othcr is thc cxtcrnal pore of a ciliatcd oviduct that originates as an open funnel in the coclom of chaetigcr 10. Thc functional and phylogcnctic significancc of thcsc structurcs is discussed.