Baterial Growth, Variation And Metabolism

Question 1

All bacteria have three major nutritional needs for growth.

What are these needs❓

Answer 1

1. Carbon (50% dry weight)
2. Nitrogen (14% dry weight)
3. Source of energy

Question 2

1. Bacteria that are able to growth using CO2 as their sole source of carbon are known as❓
2. How do they obtain energy❓

Answer 2

1. Lithotrophs/Autotrophs
2. Photosynthetically (phototrophs)

By oxidation of inorganic compounds (chemolithotrophs)

Question 3

All bacteria found in humans are❓

Answer 3

Heterotrophs

Question 4

E. coli and pseudomonas aeruginosa grow on the most simple laboratory media

True or false❓
Why❓

Answer 4

True

Growth requirements include a wide variety of organic compounds

Question 5

Haemophilus influenzae and other anaerobes can only be cultured in the lab using❓

Why❓

Answer 5

• Vitamins, purins, pyramidine and hemoglobin supplied in growth medium
• They need additional growth requirements

Question 6

Chlamydia sp. cannot be cultured on laboratory medium at all

True or false❓
How are they grown❓

Answer 6

True

Must be grown in tissue culture

Question 7

What is a “minimal” medium❓

Answer 7

• A lab culture media whose contents are simple and completely defined
• Not usually used in diagnostic micro labs

Question 8

What is a “nutrient” medium❓

Give examples

Answer 8

• made of extracts of meat or soybeans
• more complex

•eg nutrient broth, trypticase soy broth

Question 9

What is a “enriched” medium❓

Give examples

Answer 9

•contains added growth factors such as blood, vitamins and yeast extract

•eg blood agar
Chocolate agar

Question 10

What is a “selective” medium❓

Give examples

Answer 10

•contain additives that inhibit the growth of some bacteria but allow others to grow

•MCA:
MacConkey agar
Selective for gram-negative bacteria

•Colistin-nalidixic acid:
Selective for gram-positive bacteria

Question 11

What do differential mediums do❓

Give an example

Answer 11

• For visualization of metabolic differences between groups or species of bacteria
• MacConkey agar differentiates between lactose fermenters(pink) and non-lactose fermenters(clear)
• Blood agar differentiates between hemolytic and non-hemolytic organisms

Question 12

What is a transport medium used for❓

Give examples

Answer 12

•Holding medium designed to preserve the viability of microorganisms in a specimen w/o allowing multiplication

•
Stuart broth
Amies
Cary-Blair

Question 13

What three factors should be considered for bacterial culture in the lab❓

Answer 13

pH

Temperature

Gaseous composition of atmosphere

Question 14

Diagnostic laboratory media are usually adjusted to a final pH between 7.0 and 7.5

True or false❓
Why❓

Answer 14

True

Most pathogenic bacteria grow best at a neutral pH

Question 15

Psychrophilies are bacteria that❓

Answer 15

•grow optimally at 10-20C (cold temp)

Question 16

Mesophilies are bacteria that❓

Answer 16

• grow optimally at 20-40C (moderate temp)

* most bacteria that have adapted to the human body belong in this category

Question 17

Thermophilies are bacteria that❓

Answer 17

•grow optimally at 50-60C (cold temp)

Question 18

Diagnostic laboratories routinely incubate cultures for bacterial growth at ❓

Answer 18

35C

Question 19

Fungal cultures are incubated at what temperature❓

Answer 19

30C

Question 20

Classify bacteria based on their atmospheric requirements for growth

Answer 20

•Obligate aerobes:
require oxygen for growth

•Aerotolerant anaerobes/facultative aerobes:
can survive in the presence of oxygen but do not require it for metabolism eg clostridium spp.

• Obligate anaerobes: can’t survive in the presence of oxygen
• Facultative anaerobes: can grow either with or without oxygen

Question 21

There are organisms that grow best when the atmosphere is enriched with extra carbondioxide (5-10%).

What are they called❓
Give an example

Answer 21

Capnophilic organisms

Haemophilus influenza

Question 22

Microaerophilic bacteria require a reduced level of oxygen to grow.

Give an example

Answer 22

Campylobacter spp.

5-6%

Question 23

Bacteria divide by binary fission. What does “generation time” mean❓

Answer 23

The time required for one cell to divide into two cells

Question 24

What is generation time for:

A) E. coli
B) Mycobacterium tuberculosis

Answer 24

A) 20minutes

B) 24hrs

Question 25

List the phases of a bacterial growth curve and the corresponding events in those phases

Answer 25

1. Lag phase: •preparation to divide 2. Log phase: •logarithmic increase 3. Stationary phase: •limited nutrients/no growth 4. Death phase: •non-viable bacteria>viable bacteria

Question 26

Fermentation is a process of energy production carried out by what group of bacteria❓ The final electron acceptor is❓

Answer 26

Obligate and facultative anaerobes An organic compound

Question 27

The major end product of alcoholic fermentation is❓

Answer 27

Ethanol

Question 28

1. The major end product of homolactic fermentation is❓ | 2. Give some examples of bacteria that use this pathway

Answer 28

1. Lactic acid ``` 2. Streptococcus genus (all members) Lactobacillus genus (some members) ```

Question 29

1. The major end product of heterolactic fermentation is❓ | 2. Give some examples of bacteria that use this pathway

Answer 29

``` 1. Lactic acid CO2 Alcohol Formate Acetate ``` 2. Lactobacillus (some members)

Question 30

1. The major end product of propionic acid fermentation is❓ | 2. Give some examples of bacteria that use this pathway

Answer 30

1. Propionic acid 2. Propionibacterium acnes Some anaerobic non-spore forming, gram-positive bacilli

Question 31

1. The major end product of mixed acid fermentation is❓ | 2. Give some examples of bacteria that use this pathway

Answer 31

``` 1. Lactic Acetic Succinic Formic Acids ``` 2. Shigella Salmonella Escherichia

Question 32

1. The major end product of butanediol fermentation is❓ | 2. Give some examples of bacteria that use this pathway

Answer 32

1. Acetoin 2,3-butanediol 2. Klebsiella Enterobacter Serratia

Question 33

The EMP/Glycolytic pathway 1) Generates energy in the form of❓ 2) Reducing power in the form of❓ 3) Anerobic/Anaerobic❓ 4) Used by which bacteria❓

Answer 33

1. ATP 2. NADPH 3. Anaerobic 4. Entrobaceriaceae

Question 34

The pentose phosphate/phosphogluconate pathway is used by which bacteria❓

Answer 34

Heterolactic fermenting bacteria such a lactobacilli Brucella abortus

Question 35

The entner-doudoroff pathway - uses enterococcusfaecalis - is an aerobic pathway 1) True or false❓ 2) Mention bacteria that use this mechanism

Answer 35

True Pseudomonas Alcaligenes

Question 36

An important step in classifying members of the enterobacteriaceae family is the ability of the microorganism to ferment lactose True or false

Answer 36

True

Question 37

In the utilization of lactose by bacteria...

Answer 37

1. Transport of lactose across cell wall into bacterial cytoplasm by beta-galactoside permease 2. Breakage of galactoside bond to release glucose for fermentation by beta-galactosidase

Question 38

All organisms that can ferment glucose can ferment lactose True or false

Answer 38

False | Quite the contrary