Module 4 pt. 3

Question 1

essential ingredient of bacterial protoplasm

needed by actively metabolizing cells

Answer 1

Water

Question 2

minimum pressure needed to be applied to a solution to prevent the flow of water across a semipermeable membrane

Answer 2

Osmotic pressure

Question 3

organisms that can grow at relatively
high salt concentration (up to 10%)

salt-loving organisms; require relatively
high salt concentrations for growth (i.e. archea require
NaCl concentrations of 20 % or higher)

Answer 3

osmotolerant

halophiles

Question 4

Classification of Halophiles

Answer 4

low halophiles – 1-6% NaCl

mild or moderate halophiles – 6-15% NaCl

 extreme halophiles – 15-30% NaCl

Question 5

pressure exerted by standing water, in proportion to its depth

doubles with every 10 meter increase in
depth

Answer 5

Hydrostatic Pressure

Question 6

bacteria that live at high pressures

Beyond 10 MPa

52 MPa and 98C

Answer 6

piezophiles (barophiles)

Psychropiezophiles

Thermopiezophiles

Question 7

Binary Fission (5)

Answer 7

1. Replication of chromosome
2. Cell grow in size (double)
3. Septum formation
4. Completion of septum with
   formation of distinct walls
5. Cell separation

PS. Generation - interval for the formation of two cells / time required to give rise to 2 daughter cells

Question 8

Calculating Generation times

Answer 8

N = No2^n

• N = final cell number
• N0 = initial cell number
• n = number of generations that have occurred
  during the period of exponential growth

g = t/n
* g = generation time
* t = hours or minutes of exponential growth

n=3.3 (logNt-log No)

k = 0.693/g

Question 9

4 phases of bacterial growth curve:

Answer 9

– Lag
– Log or Exponential
– Stationary
– Decline/Death phase

Question 10

No significant or immediate increase
in cell numbers but there may be an increase in the
size of the cell.
◼ adaptation phase

Answer 10

Lag phase

Question 11

cells
start dividing and their number increases
exponentially
◼ organisms divide at their most rapid rate
bacteria are more susceptible to antibiotics

Answer 11

Log phase

Question 12

cell division decreases
due to depletion of nutrients & accumulation of
toxic products; inadequate oxygen supply; pH
change
▪ growth rate tapers off

Answer 12

Stationary phase

Question 13

Population decreases due to the death of cells
cells undergo lysis or involution (assume a variety of unusual shapes)

Answer 13

Decline (Death) Phase

Question 14

killing or complete elimination
of all viable microorganisms

Answer 14

sterilization

Question 15

elimination or reduction of
pathogens from inanimate objects or
surfaces

Answer 15

disinfection

Question 16

– reduction of microbial
populations to levels considered safe by
public health standards

Answer 16

sanitization

Question 17

prevention of infection in living
tissues using chemicals

Answer 17

antisepsis

Question 18

one of the most useful methods of microbial control
* reliable, safe, relatively fast, inexpensive
* use to sterilize or decrease microbial number
* moist heat or dry heat

Answer 18

HEAT

Question 19

one of the most useful methods of microbial control
* reliable, safe, relatively fast, inexpensive
* use to sterilize or decrease microbial number
* moist heat or dry heat

time required to kill all bacteria
in a particular culture at a
specified temperature

Answer 19

thermal death point

thermal death time

Question 20

• efficient penetrating properties
• destroys microorganisms by irreversibly coagulating their proteins
• boiling, pasteurization, pressurized steam

Answer 20

Moist heat

Question 21

100ºC
* destroys most bacteria
and fungi, inactivates
some viruses
* kills vegetative cells and
eukaryotic spores within
10 minutes

Answer 21

Boiling

Question 22

• use of brief heat treatment (moderately high temperature) to
  reduce the number of spoilage organisms and kill pathogens
  (Ex. Salmonella, Mycobacterium)

Answer 22

Pasteurization

Question 23

62.8ºC for 30 minutes

72ºC, 15 seconds (flash method)

140ºC -150ºC (several seconds)

Answer 23

Low temperature holding (LTH)

high-temperature-short-time (HTST) method

ultra-high-temperature (UHT) method

Question 24

• pressure cookers and autoclave
• heat water in an enclosed vessel that achieves
  temperatures above 100ºC
• 15 minutes, 15 psi, 121ºC (kills endospores and disrupts
  viruses’ nucleic acids)

Answer 24

Pressurized Steam

Question 25

• fractional steam sterilization or intermittent sterilization
• for materials that can be destroyed at more than 100 ºC
• exposure to 90-100 ºC for 30 minutes for 3 consecutive days

Answer 25

Tyndallization

Question 26

• not as efficient as wet heat (lower penetrating
  properties)
• require longer times and higher temperatures
• metal objects, glassware

Answer 26

Dry Heat

Question 27

oxidizes cell components to ashes

Answer 27

Incineration

Question 28

oxidizes cell components and irreversibly denature
proteins
* Petri dishes and glass pipettes
* 170ºC to 180ºC for 1 hour

Answer 28

Dry Heat Oven/Hot Air

Question 29

4 to 5 ºC
* limited to few
days because
bacteria and
molds continue
to grow at low
temperatures

Answer 29

Refrigeration

Question 30

• 0- -95ºC
• used to preserve food in homes and in food industries
• slows the rate of chemical reactions in bacterial cells

Answer 30

Freezing/Deep Freezing

Question 31

remove organisms from heat-sensitive fluids
* unpasteurized beer, sterilization of sugar solutions, wine
clarification
* filtration units: remove Giardia cysts and bacteria from water
* paper-thin membrane filters (polycarbonate or cellulose
nitrate): have microscopic pores that allow liquid to pass
through while trapping small particles (vacuum or pressure)
– 0.2 µm pore removes bacteria
* depth filters: trap material within thick filtration material
(cellulose fibers or diatomaceous earth) that retain
microorganisms and let fluid pass through holes

Answer 31

Fluid Filtration

Question 32

high-efficiency particulate air (HEPA): remove from air
nearly all microorganisms with diameter greater than 0.3
µm

Answer 32

Air Filtration

Question 33

used to preserve food (absence of
water inhibits action of enzymes)
* endospores survive but do not
produce toxins

Answer 33

Drying/Desiccation

Question 34

lyophilization
* drying of material from frozen state

Answer 34

Freeze-drying

Question 35

high salt/sugar concentration create hyperosmotic
medium drawing water from microorganisms
 causes plasmolysis of bacterial cells

Answer 35

Increased Osmotic Pressure

Question 36

electromagnetic radiation: radio waves, microwaves, visible
and UV light rays, X rays, gamma rays
* ionizing and non-ionizing radiation

Answer 36

Radiation

Question 37

causes biological damage directly (destroying DNA, cell
membranes) or indirectly (produce reactive molecules, i.e.
superoxide, hydroxyl free radicals/oxidizing agents)
* kills microorganisms (0.3 to 0.4 millirads) and viruses

Answer 37

Ionizing Radiation

Question 38

• 40 to 390 nm (200 nm)
• damages DNA
• effective in inactivating viruses,
  kills fewer bacteria
• microbes in air and water,
  surfaces
• poor penetration power

Answer 38

Ultraviolet Radiation

Question 39

disinfect and sterilize
* irreversibly react with proteins, DNA, cell membranes
* less reliable than heat; suitable for treating large
surfaces and heat-sensitive items; some are non-toxic;
can be used as preservatives (bacteriostatic)

Answer 39

Chemical Agents

Question 40

• 60% to 80% ethyl or isopropyl alcohol
• kill vegetative bacteria and fungi
• coagulate enzymes and other essential proteins, damage
  lipid membranes
• used as antiseptics for degerming or as disinfectants for
  treating instruments and surfaces
• non-toxic, inexpensive, no residue, evaporates quickly

Answer 40

Alcohols

Question 41

• glutaraldehyde, formaldehyde, orthophthaldehyde (OPA)
• inactivate proteins and nucleic acids
• 2% alkaline glutaraldehyde solution: widely used liquid
  sterilants for treating heat-sensitive medical items
• formalin (aqueous 37% formaldehyde): kill most forms
  of microorganisms
• toxic, irritating vapors, suspected to be carcinogenic

Answer 41

Aldehydes

Question 42

• disrupts cell membrane, denatures proteins and
  inactivates enzymes
• phenol, cresol, xylenol, triclosan

Answer 42

C. Phenols/Phenolics

Question 43

• oxidation of cell constituents
• iodine, chlorine

Answer 43

D. Halogens

Question 44

• denatures enzymes and essential proteins
• i.e. silver nitrate (prevents ophthalmic gonorrhoeae); copper
  sulfate (algicide); silver sulfadiazine (used on burns);
  merthiolate (disinfects skin mucous membranes)

Answer 44

E. Heavy Metals

Question 45

• denatures proteins
• i.e. ethylene oxide, ozone, chlorine dioxide
• for heat-sensitive items (catheters, plastic Petri dishes)

Answer 45

F. Sterilizing Gases

Question 46

• soaps and acid-anionic detergents: mechanical removal
  of microorganisms
• cationic detergents: disrupt cell membrane and denature
  proteins

Answer 46

G. Surface Active Agents or
Surfactants

Question 47

• inhibit microbial metabolism
• sorbic acid, benzoic acid, calcium propoionate
• widely used in foods/cosmetics

Answer 47

H. Organic Acids

Question 48

• oxidation of cell components
• i.e. hydrogen peroxide

Answer 48

I. Other Oxidizing Agents

Question 49

• oxidation of cell components
• i.e. hydrogen peroxide

Answer 49

I. Other Oxidizing Agents