Exam 2 (Ch. 3 Staining) Flashcards Preview

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Flashcards in Exam 2 (Ch. 3 Staining) Deck (28):
1

preparing a smear (3 steps)

1. aseptically, a thin film of a specimen is spread on a slide
2. film is air dried
3. heat fix

2

staining (def.)

procedures that use dyes to add color to microbes or cellular structures

3

dyes (def.)

chemicals added to microbes

4

name 2 types of dyes

basic dyes and acidic dyes

5

basic dyes (def. and ex.)

have positively charged ions that help them adhere to negatively charged bacteria, ex: crystal violet, methylene blue, safranin and malachite green

6

acidic dyes (2 things and ex.)

1. have negatively charged ions that are attracted to background
2. bacteria appear colorless against a stained background
ex: nigrosin

7

simple stain (2 things)

1. uses one dye
2. determines cell shapes and arrangements

8

differential stain

places bacteria into categories

9

special stain (def. and ex.)

stains specific parts of microbes, ex: Endospore stain, Negative stain and flagellar stain

10

color of gram positive

purple

11

color of gram negative stain

red

12

ex. of gram positive bacteria

Bacillus

13

ex. of gram negative bacteria

E. coli

14

reason for being gram positive

thick walls of peptidoglycan that retain the primary stain

15

reason for being gram negative

thin wals of peptidoglycan that allow decolorization

16

color of acid fast positive

bright pink

17

color of acid fast negative

blue

18

ex. of acid fast positive

Mycobacterium tuberculosis

19

reasons for acid fast results

1. some bacteria contain a waxy material called mycolic acid in their cell walls which makes staining difficult
2. once heat and carbolfuchsin are applied, acid alcohol does not decolorize the bacteria and they appear red
2. if the bacteria doesn't contain mycolic acid, carbolfuchsin is decolorized with acid alcohol and methylene blue adheres

20

if spores are present they will appear

green

21

spores can be inside or______ the cell

outside

22

for a spore stain, the bacteria cell will appear what color

red

23

name the two bacteria that produce spores

Bacillus and Clostridium

24

reasons for spore results (3 things)

1. spores are resistant to mild heat but heating in the microwave allows the spores to open
2. heat causes spores to absorb the primary stain and appear green
3. bacteria cells are decolorized with water and counterstain adheres to cells

25

the negative stain is used to determine the presence of what

capsules

26

capsules (def.)

structures that surround the cell wall

27

if a capsule is present it won't accept the stain and will appear as ______spots against a _______dark background

light; dark

28

what stain can be used to tell if a bacteria is old or young

spore stain