Microbio lab exam 1

How would you define aseptic technique?

procedure used to prevent contamination or the spread of microbes

Name 3 reasons why we practice aseptic technique in a microbiology laboratory

to prevent the contamination of cultures, to prevent to handler from exposure, and to reliable results free of contamination

How should you prepare for the day's exercise when entering lab?

take out lab manual, putting away all personal items, put on lab coat and glasses, washing hands, and putting on gloves

Why do teaching labs provide students with pens, and will confiscate personal pens if used in the laboratory?

Personal items can bring in contaminants and spread microbes in the lab and vice versa

What should you do if you have accidentally spilled some E. coli on your laboratory bench?

tell the TA

What are some good laboratory safety practices, and why are they important to practice?

disinfect bench, put belongings away, wear safety gear, and clean up, materials to prevent the spread of microbes

How would poor hand washing contribute to the spread of nosocomial infections?

it can spread germs from patient to patient, put people with compromised immune systems at risk, and increase antibiotic resistant microbes 

What was the most interesting observation you made in Exercise 1.2?

the talking plate having the most colonies and that 5 minute plate having less than 5 colonies

What is the importance of controls in your hand washing experiment?

the negative control was the person not washing their hands and the positive control was the person who did wash their hands

Why do we invert agar plates for incubation?

to prevent condensation contamination, reduce environmental contamination, and to keep colonies separated for accuracy 

Why is aseptic technique important when inoculating tubes and plates containing mediums?

to prevent contamination and ensure you grow only what is intended

How do you determine if there is growth in a liquid culture?

The liquid might be thicker, cloudy or there might be white clusters or strands in the liquid

What are some benefits of starting an experiment with a pure culture?

Pure cultures are easy for identifying microbial growth and can ensure more accurate results

What was the purpose of adding cycloheximide to some of the TSAYE plates in Exercise 1.6, Part II? Why doesn't this inhibit bacterial growth?

it inhibits fungi growth and only allows bacteria to grow due to prokaryotes having different subunits than eukaryotic subunits 

A friend tells you that they forget to flame their spreader after dipping it in ethanol. How do you think their spread plates will be affected?

there will be residual microbes and contaminate the plate, kill the species of interest, and cause inaccurate results

Are microbes present in the air? Does talking or exposing agar to the air affect the number of colonies?

Microbes are present in the air and so talking/air exposure will affect colony numbers; lab air is purified so less colonies will grow after exposure in there compared to outside air

What does the GloGerm powder / lotion represent? What was used as controls (positive /negative)?

The Glogerm represents microbes that can be present on hands, the negative control was the no Glogerm, the positive control was not washing your hands after applying Glogerm

What were the different handwashing techniques used?

1. Turn on the faucet and allow water to run until it gets warm.

2. Rinse hands under warm water to remove excess product.

3. Remove hands from under the faucet. One student should apply soap to the palm of your hands. The student who does not use soap should skip to step 7.  

4. Rub palms, back of hands, fingers and thumbs together disperse soap. Rub the soap around your hands in a similar manner to which you applied the glo-germ.

5. Continue step six until 30 seconds have passed. Then rinse hands under warm water till soap bubbles are no longer present.

6. Use a paper towel to turn off the sink.

7. Use a clean paper towel to dry your hands.

What do the results of thedifferent handwashing techniques indicate?

Participants who washed their hands with soap and warm water had little to no Glo Germ on their hands compared to the other groups. The areas of the hand that glowed were less and not as bright as compared to the control, who didn’t wash their hands at all, and to those who washed without soap. Students in the group who did not use soap still had Glo Germ remaining on their hands but their hands did not glow as brightly as the control group who did not wash their hands at all. The control group had the most fluorescence in comparison to the other groups.

What are implications for improper handwashing when leaving the lab? What about in a healthcare setting?

Improper hand washing can bring microbes into or out of the lab causing potential infection to yourself or the outside world. In a healthcare setting you can spread germs from patient to patient and create antibiotic resistant microbes.

Why might skin flora not be easily removed through proper handwashing techniques?

Some microbes are resistant to soap and water or are buried in deeper levels of the skin, some have protective barriers, and skin pattern, ridges, oil, or pores could unintentionally protect them

What does ‘transient’ microbes mean?

microbes that don’t live permanently on the skin (outermost layer) and are picked up from the environment 

What things do you let sit on the slide for 60 sec during gram staining?

crystal violet, iodine, and safranin

During gram stain when do you rinse the slide with ethanol followed by water for 15 sec?

after the iodine sat for 60 sec and was rinsed with water

What is the order for gram stain application? 

at fix, hecrystal violet, water rinse, iodine, water rinse, ethanol rinse, water rinse, safranin, water rinse

What color should gram positive be?

violet

What color should gram negative be?

pink

What does a condenser on a microscope do?

collects and concentrates light into a tight beam on the specimen 

What do objective lenses do?

magnifies specimen image

What does ocular lenses do?

allows image to be viewed

How do you solve for the total magnification? 

ocular lens magnification times the objective lens magnification 

What does cycloheximide do?

inhibits protein synthesis in eukaryotes and inhibit fungi growth

Why do you use immersion oil with the 100X objective?

Improves clarity of image, increases resolution by reducing light fraction

Why is it important to heat-fix the cells to a microscope slide?

Preserves the structure of the cell by making sure the cells don't move or wash off during staining

What are the different types of protozoan motility

1. Flagella: long tail-like extensions of the cell bran-Propel the cell forward

2. Cilia: short hair like projections around cell surface-Beat in coordinated waves

3. Pseudopodia (fake feet): extensions of the cytoplasm-Pulls the body along like crawling

Define in your own words what a ‘culture’ is

a population of microorganisms grown under controlled conditions using a nutrient medium

How do you calculate individual dilution factor (IDF)?

volume of sample transferred/ (volume of sample transferred + volume of diluent)

Why do we add immersion oil to the slide when viewing with the 100x objective?

Reduces refraction, increases amount of light entering the lens, improves resolution and clarity

What is a mordant?

Substance used during staining that helps a dye stick better to the cell

What is the mordant during gram staining?

iodine

What is the decolorizer in gram staining?

ethanol

What is the counter stain in gram staining?

safranin