5. bacterial classification & identification

Question 1

this is the classification of organism in an ordered system that indicates a natural relationship

Answer 1

bacterial taxonomy

Question 2

what are the three areas of bacterial taxonomy?

Answer 2

1. identification
2. classification
3. nomenclature

Question 3

this is the practical side of taxonomy; the process of determining that a particular isolate belongs to a recognized taxon

Answer 3

identification

Question 4

this is the categorization of organisms into taxonomic groups based on mutual similarities, genetic and evolutionary relatedness

Answer 4

classification

Question 5

this refers to the naming of an organisms by an established group of scientific and medical professionals

Answer 5

nomenclature

Question 6

what are the 4 different classical characteristics of the classification of bacteria

Answer 6

1. morphological characteristics (size and shape)
2. physiological and metabolic characteristics (motility, growth range)
3. biochemical characteristics (products bacteria gives)
4. ecological characteristics (from what part of the environment the bacteria came from)

Question 7

T/F: nomenclature of bacteria is bolded

Answer 7

false - italicized or underlined

Question 8

what is the first part of the generic name?

Answer 8

genus

Question 9

what is the second part of the generic name?

Answer 9

species

Question 10

what is the most common bacteria shape?

Answer 10

cocci - roughly spherical shapes

Question 11

what bacterial shape is a rod shape?

Answer 11

baccilli

Question 12

what does coccobacilli mean

Answer 12

short bacilli

Question 13

these are curved bacteria that can range from a gently curved shape to a corkscrew-like spiral

Answer 13

spirilla

Question 14

what is the most formative method for identifying bacteria?

Answer 14

staining and microscopy

Question 15

this type of microscopy is particularly useful for detection of bacteria, fungi and parasites.

Answer 15

light microscope

Question 16

this type of microscopy is useful for observing very small bacteria as the resolution is quite high

Answer 16

dark-field microscope

Question 17

this is similar to dark field microscopy, except that light source is ultraviolet, and the organisms are stained with fluorescent compounds. the specimen is seen as a halo around only the organism tagged with fluorescent compounds

Answer 17

fluorescence microscope

Question 18

why do we stain bacteria?

Answer 18

to become more visible under the microscope or to visualize specific parts or organelles within the cell

Question 19

this type of ionizable dyes used to stain microorganisms have positively charged groups that can bind to negatively charged structures such as DNA and cell membranes. e.g. methylene blue, basic fuchsin, crystal violet, safranin, and malachite green

Answer 19

basic dyes

Question 20

this type of ionizable dye used to stain microorganisms have negatively charged groups and can stain positively charged cell proteins and organelles. e.g. eosin, rose bengal and fuchsin

Answer 20

acid dyes

Question 21

this divides bacteria into separate groups based on staining properties

Answer 21

differential stainingg

Question 22

this is the most important type of differential staining; this divides bacteria into two groups: gram-positive and gram-negative bacteria, based on the structure of the cell wall

Answer 22

gram stain

Question 23

explain the process of gram staining

Answer 23

1. apply a basic dye (crystal violet) and iodine solution - all bacteria will be stained blue
2. decolorization step: the cells are treated with alcohol - gram positive cells will retain the crystal violet-iodine complex, remaining blue and the gram negative cells are completely decolonized by the alcohol
3. a counterstain, safranin which is red, is applied so that the gram negative cells will be stained red and the gram positive cells will appear purple

Question 24

this process is used to stain bacteria that do not simply stain with regular procedure. this method is usually used to stain mycobacterium tuberculosis (causes tuberculosis), mycobacterium leprosy (causes leprosy - affects nerves, skin eyes) and actinomycetes bacteria

Answer 24

acid fast stain (Ziehl-Neelsen method)

Question 25

the __________ (acid-fast/non-acid-fast) bacteria take the red color of carbofuchsin dye

Answer 25

acid fast bacteria

Question 26

the ________ (acid-fast/non-acid-fast) bacteria take the color of the counterstain (blue or green)

Answer 26

non-acid fast bacteria

Question 27

this stain treats the cells with tannic acid salts to increase the thickness of this structure. then it is stained with basic fuchsin and the structure will then be able to be seen in a light microscope

Answer 27

the flagella stain

Question 28

the staining of this structure is stained by Feulgen stain

Answer 28

nucleoids (DNA)

Question 29

the wall of this structure is relatively impermeable, so they can be observed as colourless areas in cells stained by conventional stains to stain this structure, malachite green or carbolfuchsin are applied with heat. the vegetative part of the cell can be stained with another counterstain after the decolorization step

Answer 29

the spore stain

Question 30

this structure is stained by the Welch method: the cells are treated with a hot crystal violet solution, they are then rinsed with a copper sulfate solution in order to remove excess crystal violet and give a dark color to the background

Answer 30

the capsule stain

Question 31

this type of medium is a medium in which the exact chemical composition is known

Answer 31

defined medium

Question 32

this type of medium is a medium in which the exact chemical constitution of the medium is not known (good for growing bacteria)

Answer 32

complex medium

Question 33

this type of media supports the growth of many different bacterial species without selection, such as blood agar and chocolate agar (blood agar boiled makes the brown color) media.

Answer 33

nonselective media

Question 34

this type of media is used to eliminate the large numbers of irrelevant bacteria in the specimens. it has an inhibitory agent that specifically selects against the growth of these irrelevant bacteria. examples of inhibitory agents: sodium azide, bile salts and colistin and nalidixic acid. examples of this media: MacConkey agar and CNA blood agar

Answer 34

selective media

Question 35

this inhibitory agent selects for gram positive over gram negative bacteria

Answer 35

sodium azide

Question 36

this inhibitory agent selects for gram negative enteric bacteria and inhibit gram negative mucosal and most gram positive bacteria

Answer 36

bile salts

Question 37

this inhibitory agent inhibits the growth of many gram negative bacteria

Answer 37

colistin and nalidixic acid

Question 38

this media is used to differentiate between bacterial groups; some bacteria produce characteristic pigments, and others produce zones of clearing surrounding colonies

Answer 38

differential media

Question 39

these are tests used for the identification of bacteria species based on the differences in the biochemical activities of different bacteria

Answer 39

biochemical test

Question 40

the bacterial species can be divided or classified into subgroups called serotype, serogroups or serovars based on the _____________________ reactions

Answer 40

immunological

Question 41

the immunologic tests are based on _____ that react with specific bacterial cell surface structures such as lipopolysaccharides (o antigen), flagella (h antigen) or capsular antigens (k antigen)

Answer 41

antibodies

Question 42

under certain circumstances (e.g. an epidemic), it is important to distinguish amoung strains of a given species or to identify a particular strain below the species level which is known as ________

Answer 42

subtyping