Midterm 1

Question 1

What are ways in which we can identify bacterial species?

Answer 1

1. Genotyping
2. Protein with mass spectroscopy
3. Phenotyping base off cell and colony morphology and biochemical characterisitics.

Question 2

In order to culture bacteria, what is required? What about on artificial media?

Answer 2

Water
Energy (carbon source)
Nitrogen source
Minerals, anions, and cations

Also need:
Correct osmolality, atmosphere and necessary biological factors like vitamins and hormones

Question 3

What assumptions do we make about colonies grown on agar plates?

Answer 3

They only contain one type of microorganism and it is a genetically identical population

Question 4

What is needed in a bacterial culture to identify the phenotype?

Answer 4

A pure culture.

Question 5

What are the phases of growth for bacteria replication in culture?

Answer 5

1. Lag
2. Exponential (LOG)
3. Stationary
4. Death

Question 6

What is the generation time of bacteria in culture?

Answer 6

The time is takes for one generation to replicate (double cell number)

Question 7

Where do we take samples from on a bacterial culture plate?

Answer 7

On the edge of the colony

Question 8

In order to grow isolated pure colonies on a plate, what substance is used and why?

Answer 8

1.5% agar because it is not used as an energy source by most bacteria and remains solid until melted at 100 ‘ C

Question 9

What is the goal when streaking on agar plates?

Answer 9

To grow multiple isolated colonies

Question 10

Explain how inoculation of specimens and streaking is performed.

Answer 10

Inoculated in 4 quadrants with a primary inoculation and 3 dilutions which is done by streaking from each quadrant.

Question 11

What does steaking give us information about?

Answer 11

The relative amount of bacteria in a clinical specimen.

Question 12

When describing what a colony looks like, what question do we ask?

Answer 12

Size in mm and shape?
Surface appearance?
Texture?
Color?

Question 13

What are the different options for describing colonial morphology?

Answer 13

The shape can be round, irregular, filamentous, rhizoid or curled. The edge can be entire, filamentous, undulated, and lobate.
The elevation can be raised, flat, convex, umbonate, or growth into medium.

Question 14

What parameters can affect the appearance of bacterial colonies?

Answer 14

Changes in the growth conditions like the carbon source, oxygen, and agar concentration.

Question 15

What can affect the way in which bacteria grow?

Answer 15

Mutations in a single gene.

Question 16

What conditions of a culture must be the same each time a culture is performed?

Answer 16

1. Formulation of medium
2. Temperature and time of incubation
3. Atmosphere

Question 17

After the colony morphology is describe , what is the next step?

Answer 17

Look at the cell morphology

Question 18

When describing cell morphology, what are streptococci? Staphylococci?

Answer 18

Streptococci is chains of cells while staphylococci are cluster of cells

Question 19

What types of stains are used in bacteriology to help identify the species?

Answer 19

1. Gram stain
2. Acid fast stain
3. Gimenez stain

Question 20

What is the size of bacteria?

Answer 20

Usually around 1 micron or 0.2mcn at 1000x)

Question 21

How does the gram stain work?

Answer 21

It differentiates two cell wall types with gram + having a thick peptidoglycan cell wall that retains crystal violet and gram - having a thin peptidoglycan cell wall that does not retain it.

Question 22

After pure cultures are grown and described, how can bacteria be differentiated into genus and species?

Answer 22

By examining the enzymatic pathways and using flow charts and pH indicators.

Question 23

Complex media

Answer 23

Contains biologics that are not completely defined

Question 24

Defined/synthetic media

Answer 24

All components of the medium are known

Question 25

Selective media

Answer 25

Blocks the growth of some types of bacteria while allowing the growth of others.

Question 26

Differential media

Answer 26

Formula design indicators where growth characteristics will differentiate two or more types of bacteria

Question 27

Describe the Trypticase soy agar media (TSA).

Answer 27

It is a complex media with enzymes that digest soy proteins

Question 28

Describe blood agar media (BAP).

Answer 28

It is a complex and differential media with a TSA base + 10% whole blood that differentiates bacteria that can lyse RBCs.

Question 29

Describe Mannitol salt agar media (MSA).

Answer 29

It is a complex, selective, and differential media with a peptone base, 7.5% Nacl to select for halophiles, and mannitol + a pH indicator phenol red.

Question 30

Describe MacConkey agar media (MAC).

Answer 30

It is a complex, selective, and differential media with a peptone base, crystal violet and bile salts to inhibit gram + bacteria, and lactose + pH indicator neutral red.

Question 31

If phenol red on MSA agar turns Yellow, what does that mean?

Answer 31

The culture is acidic which means the bacteria ferments mannitol.

Question 32

If neutral red on the MAC agar is showing basic, what color will it be?

Answer 32

Yellow, which means the bacteria does not ferment lactose

Question 33

If phenol red on MSA agar has basic colonies, what color will it turn?

Answer 33

Red to Pink. which means the bacteria does not ferment mannitol.

Question 34

If neutral red on the MAC agar turns Pink, what is going on?

Answer 34

Acidic, which means the bacteria ferments lactose.

Question 35

What bacteria does MSA agars select and differentiate?

Answer 35

Staphylococcus aureus

Question 36

What type of agar only allows gram - bacteria to grow?

Answer 36

MacConkey agar (MAC)

Question 37

What type of bacteria does the MAC agar select and differentiate for?

Answer 37

Escherichia from enterobacteriaceae

Question 38

T/F: Disease = Infection

Answer 38

False, when an animal has an infection, it does not mean it has a disease. An infection is a colonization of a pathogen that is not causing significant destruction to the host.

Question 39

What are the four things an organism needs to do to perpetuate itself in an environment?

Answer 39

1. Enter 2. Survive 3. Replicate 4. Exit and a pathogen must also cause a disease.

Question 40

Virulence factors

Answer 40

Bacterial (or other pathogen) products used to contribute to the ability of an organism to perpetuate itself and/or cause disease.

Question 41

What can virulence factors enable a pathogen to do?

Answer 41

1. Attach and/or invade host 2. Allow acquistion of nutrients 3. Inhibit phagocytic processes 4. Evade immune responses 5. Directly damage host

Question 42

T/F: Virulence factors can be surface localized or secreted by a pathogen

Answer 42

True

Question 43

What is a virulence factor that allow attachment of a microbe to a host?

Answer 43

Adhesins

Question 44

What is a virulence factor that allows a microbe to avoid the immune system and help it adhere?

Answer 44

Capsule

Question 45

What are the three immune avoidance functions of a capsule?

Answer 45

1. Antiphagocytic 2. Antigenic mimicry 3. Antigenic masking

Question 46

What are capsules made out of?

Answer 46

Most are made out of carbohydrates. some are made out of peptides.

Question 47

What are fimbriae?

Answer 47

It is a surface localized proteinaceous adhesin (organized in pilli) that mediates attachment of bacteria..they also may assist in immunologic avoidance.

Question 48

What do fimbriae attach to?

Answer 48

Carbohydrate residues of glycolipids or glycoproteins at the host cell surface.

Question 49

What are afimbrial adhesin?

Answer 49

Surface proteins not structurally related to fimbriae or organized like pili and can be a dominant protein in the bacterial cell.

Question 50

What is a biofilm?

Answer 50

Extracellular matrix created by bacteria that allows them to live on surfaces. Many species or only one species of organisms can be in a biofilm. Biofilm bacteria has many biological differences than free living bacteria.