THE ORDER MONOBLEPHARIDALES

HARPOCHYTRIUM J105 IN THE CLASSROOM

 

 Harpochytrium thalli

Harpochytrium spp. grow vegetatively as single, narrow, uniaxial thalli, sometimes arched, and pointed or rounded at the distal free end.  The thalli attach to the substrate at the basal or proximal end by excreted, non-cellular, disklike holdfasts.  The thalli resemble those of Oedogoniomyces but are much smaller.  Harpochytrium is not known to reproduce sexually.  Asexual reproduction occurs when the distal portion of the thallus forms a sporangium that opens by a circumsiscile weakening of the wall near the apex and release of posteriorly uniflagellate zoospores.  The basal vegetative portion of the thallus may continue to grow and several successive sporangia may be produced and release zoospores.

  CAUTION - Use sterile technique at all times.  Sterilize all glassware and media by autoclaving before use.

LONG TERM MAINTENANCE – If desired, culture J105 can be maintained on mPmTG agar in culture tubes with a few drops of sterile water at the base of the culture.  Tip the tubes to flood the cultures each day until growth is well stated.  Store cultures in a refrigerator.  Transfer at 3 month intervals. 

PREPARATION TIME -   Begin “Day 0” 13 days before expected use.

DAY 0 - Inoculate a Petri plate of mPmTG with a piece of culture from a stock  tube.  Make new stock tubes at the same time.  Water the inoculum in the plate with 6 or 7 drops of sterile water.  Keep in ambient light at room temperature (~22° C).  Make 1 plate for each 5 or 6 students in the class.

DAY 5 - Or as soon as growth is apparent around the piece of inoculum apply several more drops of sterile water and tip the plate slightly to spread.  Keep in ambient light at room temperature (22° C).

DAY 10 - Or when mature growth is evident, put the plate in the refrigerator for 1 or 2 days.

DAY 11 OR 12 - Bring the plate to room temperature.  Apply several drops of sterile water on the mature growth 15 - 16 hours before class observation time.

DAY 12 OR 13 - In class use a sterile scalpel to transfer a small amount of the watered portion of the culture to a microscope slide for observation; cover with coverslip.

SCHEDULE ADJUSTMENT - If careful sterile technique is observed and the plates remain uncontaminated, observation should be possible for 2 or 3 additional days.

  RECIPE for mPmTG agar for slants and plates.

MATERIALS NEEDED - In addition to screw cap test tubes (agar slants for long term maintenance), you will need enough pre-sterilized, plastic Petri plates to accommodate the number of students in the class.

REFERENCES -

Emerson, Ralph and Howard C. Whisler . 1968. Cultural studies of Oedogoniomyces and Harpochytrium, and a proposal to place them in a new order of aquatic phycomycetes.  Archiv fur Mikrobiologie 61:195 - 211. 

Gauriloff,  Larry. P., Rona  J.  Delay,  and Melvin S. Fuller. 1980. The fine structure of zoospores of Harpochytrium hedinii. Can. J. Bot. 58:2090 - 2097.

Karling, John S.1977. Chytridiomycetarum Iconographia.  Lubrecht & Cramer, Moticello , N.Y.

Travland, Linda B. and Howard C. Whisler. 1971. Ultrastructure of Harpochytrium hedinii. Mycologia 53(4):767-789.

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