General Microbiology Lab Briefing

Exercise 3 — The Myceteae

We look at two forms of fungi:  unicellular and filamentous

Unicellular fungi = yeasts — some of these are dimorphic and can form filaments.

Make wet mounts.  You may want to follow the directions in the lab book and stain your preparations with some methylene blue. These are best viewed at 400x.

• Saccharomyces – this is commonly used in baking and brewing
  • When yeast divide by mitosis their cytoplasm divides unequally (cytokinesis is unequal) — this is called budding. [ Sometimes I think they look like Mickey Mouse or Mickey Mouse with one ear.]
• Candida – this variety of yeast may form chains of elongated cells that look like filaments (filaments = hyphae); they are called pseudohyphae.  Candida can cause opportunistic yeast infections of the mouth or vagina.
• Sourdough Sponge — consisting of Saccharomyces and a rod-shaped bacterium (Lactobacillus).  You will also see colorless round structures that are larger than the yeast.  They are grains of the flour.
  • The sponge is kept alive by feeding it flour and warm water periodically and leaving it in a warm place to “work”.  Working consists of yeast fermenting the sugars in the flour and producing alcohol which the bacteria ferment to form acids (like lactic acid).

Follow the directions in the lab book and take a swab sample from your tongue and plate it out on a plate (petri dish) containing Sabouraud Dextrose (Sab-Dex) agar.  We will incubate this at 37 degrees C for about a week.

Filamentous Fungi  — 3 genera

Prepared slides — each slide contains all three genera and their order on the slide corresponds to their order on the slide label.

• Aspergillus (best viewed at 100x)
• Rhizopus (best viewed at 100x)
• Penicillium (best viewed at 400x)

Live cultures grown in large test tubes on Sab-Dex agar.  Note the appearance of the underside of the growth.

Exercise 4 — Helminthes (Parasitic Worms)

Most of these can be viewed at 40x or 100x at the most.  Be sure to look at preserved specimens as well.  [You don't need to draw the preserved specimens.]

• Cestodes (Tapeworms)
  • Scolex (head) and proglottids (segments)
  • Gravid (egg-containing) proglottids
• Trematodes (Flukes)
  • Chinese Liver Fluke (Clinorchis)
    • Whole mount
    • Ova
  • Sheep Liver Fluke (Fasciola)
    • Cerceriae, Miracidia, Metacercariae – all from photomicrographs available in Vancko Hall.
  • Blood Fluke (Schistosoma japonicum)
    • Male and Female
• Nematodes (round worms)
  • Trichinella spiralis
    • in muscle
    • isolated larvae

NOTES:

1. You should have completed Exercises 1 and 2 and answered all of the questions at the end of these two exercises.
2. A clarification of question 4 on page 22 asks about systemic protozoan diseases.  Systemic means system-wide — those that infect the whole body.  Malaria is a systemic disease; giardiasis, amoebic dysentery, and cryptosporidiosis are not.

This week you’re looking at members of the Protista!

You should have your laboratory supplies with you this week — including a lab coat, scrubs, etc and your lab book!

BE SURE TO READ THE LAB INTRODUCTION FOR THIS EXERCISE.  If you have a “Perspectives” book, this is a good day to bring it to lab.

For the live material you should make wet mounts (drop of specimen on a slide and place a cover slip over it) or a hanging drop (drop of specimen on a cover slip then place the depression of a depression slide over it and invert both).

Protozoa –

Living Specimens — be sure you look at these on Tuesday, they won’t last till Thursday:

• Amoeba – slow-moving but difficult to find in the jar of specimens.  I may help you out here by using a dissecting microscope and pipet to suck out individuals for you to see.  Scan at 40x and view at 100x and maybe 400x.
• Paramecium – fast-moving slipper-like protozoans that are covered with cilia.  You might want to put a small drop of Proto-Slo on the slide with the drop of specimen to slow them down.  Scan at 40x and observe at 100x and 400x.
• Vorticella — a stalked, ciliated protozoan.  Looks like a wine goblet.  Scat at 40x and observe at 100x and 400x.

Prepared Slides:

• Trypanosoma – a blood parasite.  Note (and label) the trypanosomes between the red blood cells (400x); What diseases do these cause?
• Trichomonas vaginalis — cause the sexually transmitted trichomoniasis.  400x

Algae –

Live Specimens (Tuesday)

• Spirogyra – a filamentous green alga with spiral-shaped chloroplasts.  View at 100x.
• Closterium – cigar-shaped green algae.  100x or 400x.
• Live diatoms — maybe if I can get some; they will be available on Thursday.

Prepared Slides

• Volvox – a spherical colony of green flagellated cells.  100x?
• Spirogyra — much like the live specimens. 100x

Cyanobacteria –

Live specimens and prepared slides of

• Oscillatoria – long thin filaments rather blue-green in color.  [Once these were included in the “blue-green algae” but now they are considered to be bacteria.  400x

This is a lab briefing blog.

• I publish the blog each week, usually on Friday.
• It contains information for the next week’s lab.
• It is sort of a “heads up” on what we are going to be  doing.
• It is NOT a substitute for reading the lab book.

Why a blog?

• Because you can enable a RSS Feed for the blog which means that as I post to it, you can get a message showing I have done so.
• Because I like it!

About Micro Lab

1. First of all Microbiology lab meets twice a week..  This is so you can set up experiments one day and let them incubate so you can check the results during the “come-back” lab.
2. Yes, lab does meet the first week of the semester.
3. Be sure that you have a lab coat (or scrubs or lab apron), a NEW lab notebook, and a lab kit which contains slides, cover slips, lens paper, a wax pencil, and a depression slide.
4. You should have these by the start of the second week’s lab.

Week One’s Lab:

• This week is important because we’re going over the basics of lab procedures and lab safety.
• We’re also doing exercise 1:  Microscopy.
  • This includes the proper use and care of the most important tool in Microbiology, the microscope.
  • You’ll use the microscope to look at a prepared slide of blood.
    • Draw what you see at all 4 magnifications (40x, 100x, 400x, and 1,000x).
    • Note that after this you only need to draw what you see at the best magnification to view the specimen (for bacteria that is 1,000x, for protozoa it is usually 400x).
    • Label your drawings.
    • AND be sure to describe in words what you see.  This is an important practice to do because you are seeing things you have not seen before and will be expected to do a number of reports that include your detailed observations!
• For the comeback lab you’ll be looking at hanging drop preparations of a Hay Infusion.
  • Be sure to look at your lab book for how to make a hanging drop preparation.
  • A hay infusion contains dried grass (hay) plus water from a pond or stream that has been allowed to sit at room temperature for at least a week.
  • It will contain a number of kinds of organisms including bacteria and protozoans.  (Some may also contain fungal filaments).
    • Be sure you take note of the relative sizes of the organism that you see.