EXAM 2 Flashcards
(49 cards)
1
Q
what are Psychrophiles?
A
Cold loving organisms (Cause spoilage in the fridge)
2
Q
what are Mesophiles?
A
Moderate temp loving organisms (Optimal growth temp is body temp)
3
Q
what are Thermophiles?
A
Heat loving organisms (55 degrees C) (Not much disease in humans)
4
Q
what are Hyperthermophiles?
A
Ultra heat loving organisms (over 80 degrees C)
5
Q
at what pH does bacteria grow?
A
- 6.5 - 7.5
Acidophiles - remarkably tolerant of acidity - Acidity is used to prevent spoilage
6
Q
what are Extreme or obligate halophiles ?
A
REQUIRE high osmotic pressure (high salt)
7
Q
what are Facultative halophiles?
A
TOLERATE high osmotic pressure (high salt)
8
Q
what are Obligate aerobes?
A
require oxygen for metabolism
9
Q
what are Obligate anaerobes?
A
– can’t tolerate oxygen
- Unable to metabolize oxygen and are harmed by it
10
Q
what are Facultative anaerobes?
A
-can grow with or without oxygen
- Grow via fermentation or anaerobic respiration with no oxygen
11
Q
what are Aerotolerant anaerobes?
A
tolerate but cannot use oxygen
11
Q
what are Microaerophiles?
A
require oxygen concentration lower than air
12
Q
what are biofilms?
A
- microbes in nature that are found in communities called Biofilms
- Form slime or hydrogels that adhere to surfaces
- Biological systems with benefits of multicellular organisms
- Usually attached, ie. teeth, medical devices, etc…
13
Q
what happens if the culture medium is solid? (Agar)
A
- Complex polysaccharide
- Used as a solidifying agent for culture media in Petri plates, slants, and deeps (also used in ice cream and jelly)
- Generally not metabolized by microbes
- Liquefies at 100C & solidifies at ~40C
14
Q
what is culture media?
A
- Culture medium: nutrients prepared for microbial growth
- Sterile: no living microbes
- Inoculum: introduction of microbes into a medium
- Culture: microbes growing in or on a culture medium
15
Q
what is chemically defined media?
A
exact chemical composition is known
16
Q
what is complex media?
A
extracts and digests of yeasts, meat, or plants; chemical composition varies batch to batch
17
Q
what is Selective media?
A
- Suppress unwanted microbes and encourage desired microbes
- Contain inhibitors to suppress growth
18
Q
what is Differential media?
A
Allow distinguishing of colonies of different microbes on the same plate
19
Q
what is a colony?
A
- a population of cells arising from a single cell or endospore
- Only about 1% of bacteria produce colonies with current culturing techniques
20
Q
what is the streak plate method?
A
used to isolate individual colonies
21
Q
What are the biosafety levels?
A
- BSL-1: no special precautions; basic teaching labs
- BSL-2: lab coat, gloves, possibly eye protection
- BSL-3: biosafety cabinets to prevent airborne transmission
- BSL-4: sealed, negative pressure; “hot zone”
22
Q
how do you preserve bacteria cultures?
A
- Deep-freezing: –50° to –95°C
- Lyophilization (freeze-drying): frozen (–54° to –72°C) and dehydrated in a vacuum
- Microbes can stay alive for years, just need to rehydrate
23
Q
what is bacterial growth?
A
increase in # of cells
24
what is Binary fission?
- normal reproduction for bacteria
- slide 30
25
what are the phases of growth?
- Lag: Intense activity preparing for population growth, but no increase in population.
- Log: Logarithmic, or exponential, increase in population
- Stationary: Period of equilibrium; microbial deaths balance production of new cells
- Death: Population is decreasing at a logarithmic rate
25
What is the DIRECT measuring of microbial growth?
- Plate count – dilute culture and plate, then count colonies, CFUs (To ensure the right number of colonies, the original inoculum must be diluted via serial dilution)
- Filtration – filter liquid – filter catches microbes, place filter on plate, then count colonies
- MPN – dilute greatly, culture, look for growth in each culture, statistical estimation
- Direct microscopic count - bacterial suspension onto marked slide, count cells
26
What is the INDIRECT measuring of microbial growth?
- Turbidity = cloudiness of culture
- Use a spectrophotometer – measure light passing through culture
- Measuring metabolic activity – oxygen consumption, acid production, etc…
- Measuring dry weight – bacteria are filtered, dried and weighed
27
what is Asepsis?
- absence of significant contamination
- Aseptic techniques are necessary for work with microbial cultures
- Aseptic surgery techniques prevent the microbial contamination of wounds
28
what is Sepsis?
bacterial contamination
29
what is Sterilization?
removing and destroying all microbial life
30
what is Commercial sterilization?
killing C. botulinum endospores from canned goods
31
what is Disinfection?
destroying harmful microorganisms on an inanimate object
32
what is Antisepsis?
destroying harmful microorganisms on living tissue
33
what is Degerming?
the mechanical removal of microbes from a limited area
34
what is Sanitization?
lowering microbial counts to safe levels
35
HEAT methods of microbial control
** Heat denatures enzymes
- Thermal death point (TDP): lowest temperature at which all cells in a culture are killed in 10 min
- Thermal death time (TDT): minimal time for all bacteria in a culture to be killed at a particular temperature
- Decimal reduction time (DRT): minutes to kill 90% of a population at a given temperature
35
what is the difference between -cide & -stasis?
-cide: treatments that kill microbes
-stasis: inhibiting the growth, not killing
36
Actions of Microbial Control Agents
- Alteration of membrane permeability
- Damage to proteins (enzymes)
- Damage to nucleic acids
(Some control agents damage RNA and DNA)
36
what does the Effectiveness of treatment depends on?
- Number of microbes present
Environment
- The presence of organic matter can inhibit antimicrobials
- Time of exposure – usually die at a constant rate
- Microbial characteristics
Gram-? Endospores? Mycobacterium?
37
Moist Heat Sterilization
- autoclave: steam under pressure
121°C at 15 psi for 15 min
- Kills all organisms and endospores
- Steam must contact the item's surface!
37
pasteurization
- short, high heat treatment
- Reduces spoilage organisms and pathogens
- Equivalent treatments
63°C for 30 min
- High-temperature short-time (HTST): 72°C for 15 sec
- Ultra-high-temperature (UHT): 140oC for 4 sec
38
Radiation
- Ionizing radiation (X rays, gamma rays, electron beams)
**Ionizes water to create reactive/damaging hydroxyl radicals
**Causes mutations in DNA
**Low level ionizing radiation is used in food industry- spices, meat, produce
- Nonionizing radiation (UV, 260 nm)
**Damages DNA by creating thymine dimers
**Disinfect vaccines, germicidal lamps
- Microwaves kill by heat
**Not especially antimicrobial, uneven heating a concern
39
Physical Methods of Microbial Control
- Low temperature - has a bacteriostatic effect
**Refrigeration – static, usually wont kill
**Deep-freezing – slow freezing is more harmful
**Lyophilization - freeze drying
- Desiccation: absence of water prevents metabolism – can remain viable
- Osmotic pressure uses salts and sugars to create hypertonic environment; causes plasmolysis
40
Chemical Methods of Microbial Control
- Phenols
- Biguanides - chlorhexidine
- Halogens
- Alcohols - 70% better than 90
- Heavy Metals - gold (Au)
- Surface Active Agents
- Soaps, quats = cationic detergents
- Aldehydes
- Chemical Food Preservatives – - Nitrates/nitrites, organic acids
- Ethylene Oxide Gas Treatment
41
The Disk-Diffusion Method
- Evaluates effectiveness of chemical agents
- Filter paper disks are soaked in a chemical and placed on a culture
- Look for zone of inhibition around disks
(Size of zone doesn’t matter)
42
Phenols
- is a standard of comparison, rarely used due to irritating qualities and odor
- Disrupts lipids of plasma membranes, causing leakage
- Phenolics – altered phenol
Can be less irritating and/or better antimicrobial action
(essential oils)
- Bisphenols – hexachlorophene & triclosan(antibacterial soaps, toothpastes, and mouthwash)
43
Hydrogen Perioxide
- Oxidizing agents
- Used for contaminated surfaces and food packaging
- Effective on inanimate objects
- Rapidly degrades into water and oxygen
43
Heavy metals
Oligodynamic action - very small amounts exert antimicrobial activity esp. Ag and Cu
Denature enzymes / proteins
Ag, Cu, Hg, Zn, Au
