The objective of this program is to explore the molecular basis and physiological functions of ion transport in eukaryotic microorganisms, fungi in particular. The water mold Blastocladiella emersonii, well known to developmental biologists for its remarkable life cycle, is also a favorable organism for electrophysiological research. Earlier work from this laboratory has suggested that the organism drives a combined circulation of potassium ions and protons with the aid of a potassium-translocating ATPase. We shall continue ongoing efforts to isolate the plasma membrane and to characterize its ion-transport ATPases. The findings will serve as the basis for examining the movements of K+, M+, Na+ and Ca2+ ions in the context of the cell's growth and development. Circumstantial evidence from several laboratories implicated protons and calcium ions in apical extension and the control of branching. Experiments with Neurospora and Achlya will explore the effects of ionophores on growth and cytoplasmic calcium levels. We shall seek to discover whether changes in the calcium level serve as regulatory signals; whether colonial growth in certain mutants reflects altered ion fluxes; whether there is a gradient of Ca2+ ions within hyphae and what this has to do with polarized growth; and how ionic signals interact with other signals to create the integrated process that we call growth.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
7R01AI003568-27
Application #
3124138
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Project Start
1989-07-01
Project End
1991-03-30
Budget Start
1989-07-01
Budget End
1991-03-30
Support Year
27
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Colorado State University-Fort Collins
Department
Type
Schools of Arts and Sciences
DUNS #
112617480
City
Fort Collins
State
CO
Country
United States
Zip Code
80523
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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