Review, Midterm Lab Exam

Question 1

Bacterial proteins (peptidoglycan) are coagulated and fixed to the glass surface.

Answer 1

Heat fixation

Question 2

Positively charged Chromagen (nucleic acid’s and certain cell wall components carry a negative charge) strongly bind to the cationic chromogen (simple staining indicates morphology and arrangement) Crystal violet, methylene blue.

Answer 2

Basic stains

Question 3

Negatively charged chromogen will not penetrate cells because of the negative charge on the surface of bacteria. Unstained cells against colored background. Negrosin

Answer 3

Negative stains

Question 4

Alcohol increases the porosity of the cell wall by dissolving the lipids in the outer layer and dehydrating proteins. CV – I complex can be removed from the thinner and less highly cross-linked peptidoglycan layer. Which facilitates release of the unbound CV – I complex. Grams positive cells with their thicker peptidoglycan retain CV – I.

Answer 4

Graham negative cells

Question 5

Dehydrating effect of alcohol reduces pores so CV – I is retained. Stain is difficult to remove.

Answer 5

Gram-positive cells

Question 6

Morphology and arrangement – basic dyes positively charged chromogen

Answer 6

Simple stain

Question 7

Smear, mix with water, air dry, heatfix, stain, one minute, water, blot.

Answer 7

Also simple stain

Question 8

These are metabolically inactive, highly resistant to unfavorable conditions (exhaustion of carbon source). Impervious layers called spore coats. Resist damage by heat, freezing, desiccation, radiation, and microbiological stains. May germinate later into vegetative cell. Not reproduction.Malachite green

Answer 8

Spore stain

Question 9

of Colonies x milliliters x dilution factor = cells per milliliter

Answer 9

Calculating cells per mill

Question 10

Thick peptidoglycan (cell wall) lattice over plasma membrane. Peptidoglycan = Nam plus nag carbohydrates. Proteins cross-link and anchor peptidoglycan into plasma membrane.

Answer 10

Gram + bacterial cell wall

Question 11

Cell wall consists of (outer membrane & peptidoglycan) over plasma membrane. Phospholipid/peptidoglycan sandwich.

Answer 11

Graham - bacteria cell wall

Question 12

Obligate aerobes. Obligate anaerobes. Facultative anaerobes.

Answer 12

Be familiar with test tube arrangement.

Question 13

Produces a characteristic change in the appearance of bacterial growth and medium surrounding the colonies which permits differentiation. Eosin – methylene blue auger

Answer 13

Differential media

Question 14

Designed to isolate specific groups of bacteria. incorporates chemical substance that inhibits the growth of one type of bacteria while permitting the growth of another Facilitating bacterial isolation. 7.5% sodium chloride auger

Answer 14

Selective media

Question 15

In blood agar (and enriched media) alpha hemolysis is the incomplete lysis of red blood cells with reduction of hemoglobin to methemoglobin resulting in a greenish halo around the bacterial growth. Beta hemolysis is the lysis of red blood cells with the complete distruction and use of hemoglobin resulting in a clear zone surrounding the colonies.

Answer 15

The difference between alpha and beta hemolysis

Question 16

Fermentation is a biooxidative process not requiring oxygen in which an organic substrate serves as the final electron acceptor. Aerobic respiration is biooxidation in which molecular oxygen can serve as the final electron acceptor.

Answer 16

Main difference between aerobic respiration and fermentation

Question 17

The bending power of light passing through air from the glass slide to the objective lens, immersion oil minimizes the amount of refracted (lost light).

Answer 17

Refractive index