Microbial Growth and Its Control Lesson 2

Question 1

increase in number not size

Answer 1

Microbial Growth

Question 2

Binary Fission

Answer 2

1. Cell elongates and DNA is replicated
2. Plasma membrane begins to constrict and new wall is made
3. Cross-wall forms, completely separating the two DNA copies
4. Cell separate

Question 3

time required for a cell to divide (and its population to double)

Answer 3

Generation Time

Question 4

Phases of Growth

Answer 4

1. Lag Phase
2. Log Phase
3. Stationary Phase
4. Death Phase

Question 5

The Requirements for Microbial
Growth

Answer 5

Physical Requirements
Chemical Requirements

Question 6

Physical Requirements

Answer 6

◦ Temperature
◦ pH
◦ Osmotic pressure

Question 7

Chemical Requirements

Answer 7

◦ C
◦ N, S, P
◦ Trace elements
◦ O2
◦ Organic growth factors

Question 8

Temperature in this range destroy most microbes, although lower temperatures take more time

Answer 8

60-130 C

Question 9

Very slow bacterial growth

Answer 9

50-60 C

Question 10

Rapid growth of bacteria; some may produce toxins

Answer 10

15-55 C

Question 11

Many bacteria survive; some may grow.

Answer 11

-5 - 15 C

Question 12

Refrigerator temperatures; may allow slow growth of spoilage bacteria, very few pathogens

Answer 12

0-5 C

Question 13

No significant growth below freezing

Answer 13

0 to -30 C

Question 14

PH

Answer 14

most bacteria– 6.5-7.5
◦ cultured bacteria produce acids that inhibit own growth; hence, buffers are used

acidophiles– even up to 1

fungi– wider range, usually 5-6

Question 15

Osmotic Pressure

Answer 15

High osmotic pressure (hypertonic) → plasmolysis (shrinkage)
◦ adding salt can preserve food

Low osmotic pressure (hypotonic) → swelling

Extreme halophiles– can grow at high salt concentrations

Question 16

• plasmolysis (shrinkage)
• adding salt can preserve food

Answer 16

High osmotic pressure (hypertonic)

Question 17

swelling

Answer 17

Low osmotic pressure (hypotonic)

Question 18

can grow at high salt concentrations

Answer 18

Extreme halophiles

Question 19

• the structural backbone of living matter
• half the dry weight of bacterial cell

Answer 19

Carbon

Question 20

2 types of C sources:

Answer 20

Chemoheterotrophs
Chemoautotrophs and photoautotrophs

Question 21

get C from organic materials such as proteins,
carbohydrates, and lipids

Answer 21

Chemoheterotrophs

Question 22

get C from CO2

Answer 22

Chemoautotrophs and photoautotrophs

Question 23

Nitrogen, Sulfur, and Phosphorus

Answer 23

needed in the synthesis of biomolecules

Question 24

elements required in small amounts e.g. Fe, Cu, Mo, Zn usually needed as cofactors

Answer 24

Trace Elements

Question 25

Microbes that use molecular oxygen (aerobes) extract more energy from nutrients than microbes that do not use oxygen (anaerobes).

Answer 25

Oxygen

Question 26

essential organic compounds e.g. vitamins, amino acids, pyrimidines, purines

Answer 26

Organic Growth Factors

Question 27

thin, slimy layer encasing bacteria that adheres to a surface

Answer 27

Biofilm

Question 28

a hydrogel, which is a complex polymer (polysaccharides, DNA and proteins) containing many times its dry weight in water

Answer 28

Biofilm

Question 29

allows cell-to-cell chemical communication

Answer 29

Biofilm

Question 30

probably 1000 times more resistant to microbicides

Answer 30

Biofilm

Question 31

e.g., Streptococcus mutans– form biofilms on teeth and gums, contributing to dental plaque and dental caries

Answer 31

Biofilm

Question 32

Destruction or removal of all forms of microbial life, including endospores but with the possible exception of prions.

Answer 32

Sterilization

Question 33

Usually done by stream under pressure or a sterilizing gas such as ethylene oxide.

Answer 33

Sterilization

Question 34

Sufficient heat treatment to kill endospores of Clostridium botulinum in canned food

Answer 34

Commercial Sterilization

Question 35

More-resistant endospores of thermophilic bacteria may survive, but they will not germinate and grow under normal storage conditions

Answer 35

Commercial Sterilization

Question 36

Destruction of vegetative pathogens on inanimate objects.

Answer 36

Disinfection

Question 37

May make use of physical or chemical methods.

Answer 37

Disinfection

Question 38

Destruction of vegetative pathogens on livinf tissue

Answer 38

Antisepsis

Question 39

Treatment is almost always by chemical antimicrobials

Answer 39

Antisepsis

Question 40

Removal of microbes from a limited area, such as the skin around an injection site

Answer 40

Degerming

Question 41

Mostly a mechanical removal by soap and water or an alcohol-soaked swab

Answer 41

Degerming

Question 42

Treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels.

Answer 42

Sanitization

Question 43

May be done with high-temperature washing or by dipping into a chemical disinfectant

Answer 43

Sanitization

Question 44

– kills microorganisms

Answer 44

Biocide/germicide

Question 45

- inhibits the growth and multiplication of bacteria

Answer 45

Static

Question 46

– bacterial contamination

Answer 46

Sepsis

Question 47

– absence of contamination

Answer 47

Asepsis

Question 48

– practices that exclude all organisms from contaminating media or contacting living tissues

Answer 48

Aseptic Technique