Is Yeast Alive? Lab

This is the first lab I run every semester because it can be done with just yeast before fees have been collected to purchase organisms with. This semester, I bought two different kinds of water balloons at Wally World. The ones that come in the large plastic container (kind of like a tennis ball container) were TOO small to even fit over the mouth of the test tubes. The other ones didn't work very well either. I think last semester, I just bought small regular balloons and these seemed to work better.

One change I made to the procedures on Part 1 was to mix the yeast and water in a beaker instead of trying to mix it in a test tube. This cut down on prep time for the kids and worked just as well. They then just evenly distributed the yeast mixture into the four test tubes. I will do this again, so I need to change the procedures before printing them out next semester.

One student asked me how we knew that the production of the gas was an indication of life instead of just an indication of a chemical reaction. I told him that is one reason we are doing Part 2 of the lab also (which will show evidence of growth).

Infectious Disease Simulation

This activity was great fun and really drove home how rapidly infectious disease can spread throughout a community. I used the small plastic beakers instead of buying Dixie cups and they worked fine. After each round, I had students clean out their cups well and return them to the front demo desk where I refilled them with either water or .1M NaOH (only one cup). We actually had time to run through the lab enough times to where they did 5 interactions on the last round which infected all but about three people in the classroom, which was pretty powerful. Great Lab!

Differential and Selective Media Lab

This lab worked beautifully! We used Staphylococcus epidermidis, E. coli, Serratia marcescens, and Enterobacter aerogenes. All of them responded exactly as expected.

MacConkey and EMB agar

Next week's lab on Differential and Selective Media calls for MacConkey and EMB agar. I made 800 mL of both this morning.

MacConkey--40 g powder in 800 mL of distilled water

EMB agar--28.8 g powder in 800 mL of distilled water

Both required heating and stirring until dissolved.

I only had 100 g of each of these powders, so if I have two sections of Micro in the fall, I will need to order a bottle of each.

Protozoans Lab a HUGE Hit!

The kids had an absolute blast today looking at all the different types of protozoans, algae, etc. that I ordered in for today's lab. In fact they had so much fun that they want to continue this same lab on Monday. Sure hope the specimens can live until then!

Finding time for transfers

I am trying to find time to make transfers of my original cultures to try to keep viable, pure cultures on hand, but there is just NO time! I did start making them today, but did not get finished before someone grabbed me for yet another something I HAD to do for the Academy. Oh, well, maybe I'll get to finish them tomorrow. These slants are perfect though, so I need to be sure to use that recipe next semester or whenever else I need to make more slants.

Making Nutrient Agar Slants

The nutrient agar slants I made last time didn't set well, so I'm doing it a little differently this morning. Here's the recipe I found:

23 g. nutrient agar per 1000 mL
BOIL and STIR until thoroughly dissolved.
Aliquot 5-7 mL per screw-cap test tube.
Sterilize
Set out to cool on a slant.

Hopefully this will work better.