The broad objectives of this program are to explore the molecular and physiological functions of ion transport in microorganisms. There is now strong evidence that in bacteria the linkage between transport systems and cellular metabolism is usually indirect, effected by the circulation of protons across the cytoplasmic membrane (chemiosmotic theory). More recently it has become clear that bacteria also possess an array of transport systems that depend on the cells' ATP supply. Many ion transport systems, including those for K+ and (in some organisms) Na+ and Pi, are ATPlinked. The nature and mechanism of these systems are the primary focus of this research. Research will be conducted along two lines. The major line concerns ion transport in the Gram-positive bacterium Streptococcus faecalis, which has both technical and conceptual advantages. We will pursue our discovery that sodium is expelled by an ATPdriven electroneutral pump (probably by exchange for H+), by means of concurrent experiments with intact cells and everted membrane vesicles. Subsequently, emphasis will shift to potassium transport which is known to require the collaboration of ATP and the protonmotive force but whose mechanism remains elusive. The second line of research is concerned with ion transport in the eukaryotic water mold Blastocladiella emersonii. Electrophysiological studies presently underway indicate that in this organism the membrane potential arises by K+ diffusion, and point to a novel pattern of chemiosmotic ion currents. I hope to explore both the genesis of the ion circulation and its possible role in the transport of nutrients through the rhizoid filaments to the thallus.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI003568-22
Application #
3124134
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Project Start
1978-12-01
Project End
1987-02-28
Budget Start
1985-03-01
Budget End
1986-02-28
Support Year
22
Fiscal Year
1985
Total Cost
Indirect Cost
Name
National Jewish Health
Department
Type
DUNS #
City
Denver
State
CO
Country
United States
Zip Code
80206
Harold, F M (1991) Biochemical topology: from vectorial metabolism to morphogenesis. Biosci Rep 11:347-82;discussion 382-5
Harold, F M (1990) To shape a cell: an inquiry into the causes of morphogenesis of microorganisms. Microbiol Rev 54:381-431
Schreurs, W J; Harold, R L; Harold, F M (1989) Chemotropism and branching as alternative responses of Achlya bisexualis to amino acids. J Gen Microbiol 135:2519-28
Thiel, R; Schreurs, W J; Harold, F M (1988) Transcellular ion currents during sporangium development in the water mould Achlya bisexualis. J Gen Microbiol 134:1089-97
Schmid, J; Harold, F M (1988) Dual roles for calcium ions in apical growth of Neurospora crassa. J Gen Microbiol 134:2623-31
Kropf, D L (1986) Electrophysiological properties of Achlya hyphae: ionic currents studied by intracellular potential recording. J Cell Biol 102:1209-16
Caldwell, J H; Van Brunt, J; Harold, F M (1986) Calcium-dependent anion channel in the water mold, Blastocladiella emersonii. J Membr Biol 89:85-97
Harold, R L; Harold, F M (1986) Ionophores and cytochalasins modulate branching in Achlya bisexualis. J Gen Microbiol 132:213-9
Kakinuma, Y; Harold, F M (1985) ATP-driven exchange of Na+ and K+ ions by Streptococcus faecalis. J Biol Chem 260:2086-91
Harold, F M; Schreurs, W J; Harold, R L et al. (1985) Electrobiology of fungal hyphae. Microbiol Sci 2:363-6

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