September 12 Lab

The goals for this lab were to cover:

• Subculturing 
• Aspergillus cultures
• Riddell mounts
• Hyphal growth
• Media Variants

For subculturing, you want to select the appropriate media (more on this later) and under sterile conditions, transfer a small section of previously plated fungus on to the new media. This is a pretty simple procedure, and this will be necessary when isolating fungi for our unknowns.

We also looked at a number of Aspergillus species to see if we could tell the difference in fungi of similar structure. This group has simple, round spores that make identification difficult unless the intact conidiophore is viewed. This turned out to be fairly difficult for me to tell the difference, but I think as I get better at preparing slides to look at my specimens, this will become easier. Here are some drawings of the various samples we looked at.

Aspergillus sojae, squash mount.

Aspergillus flavus (atoxigenic strain), squash mount

Aspergillus oryzae, agar block.

Aspergillus paraciticus, squash mount.

Aspergillus nidulans, squash mount

Aspergillus niger, squash mount

Aspergillus tamari,  squash mount

     The Riddell mount is another technique we learned in the quest to better view conidiophores. The classical version of this technique is to place a cut piece of agar on to a microscope slide that will be placed in a clean petri dish on top of a bent glass rod. The glass rod elevates the slide so that water can be added to the petri dish to avoid letting the agar dry out. From here, the fungus in question will be transfered to the sides of the cut agar block, and then a cover slip will be placed on top of this agar block. After a few days, as the fungus begins to grow, some growth should come in contact with the cover slip. This cover slip can then be transfered to a new, clean slide with a drop of water and be viewed under the scope. It is ideal to make several of these mounts that can be viewed over the course of a few days to catch the optimal stage in growth for viewing. There is a modified version to these mounts that requires less supplies and time. Simply take a clean agar plate, cut a few blocks from the edge, and then place these blocks on the side of the plate that has uncut agar. This method will help to  keep moisture in the agar block.

     Finally, we also learned about various types of media that we can use to grow our various fungi with. The best media may be different for each fungus and the use of several types may be necessary to find the right media to properly grow a particular fungus. More on the various types of media can be found here:

http://classes.midlandstech.com/carterp/Courses/bio225/chap12/fungalculturemedia.htm