Microbiology 3 Flashcards
1
Q
Endospores
A
- Resting form of some bacterial cells
- Produced only by two Gram+ Genera e.g. Bacillus and Clostridium
2
Q
Funtion of endpores
A
- Mechanism of survival to adverse environmental conditions that would be lethal for the bacteria
- nutrients depletion
- Environmental stresses (extreme temperature, pH),
- Chemical stresses
- Resistant som can survive for long periods of time
3
Q
Sporulation
A
- Endspores are not a a form of reproduction as only one new cell germinates from each endpore
- process of differentiation, normally starts when growth ceases due to lack of nutrients or environmental stress activate genes for differentiation
4
Q
Germination
A
- When endospores return to its vegitative state
5
Q
Endospore structure
A
- Ovoid shape and a multi-layered structure
6
Q
1st layer
Core walls
A
- Innermost later Core containing DNA, ribosomes, essential proteins and large depots of calcium dipicolinate
7
Q
2nd layer
Cortex
A
made of peptidoglycan
8
Q
3rd layer
Spore coat
A
- fairly thick, and impermeable layer.
- It confers resistance to chemicals/antibiotics
9
Q
4th layer
Exosporium
A
Thin covering, not always present
10
Q
Germination
A
- Process of an endospore that revert back to a vegetative cell very rapidly through removal of the stress inducer
- requires an activation step (heating to damage the spore coat), which is reversible
- Core is hydrated, spore coats are cracked and the
cell metabolism is restored
11
Q
3 steps of germination
A
- Activation
- Initiation
- Outgrowth
12
Q
Clostridium botulinum and Clostridium perfingens
A
- Causes flaccid paralysis muscle weakness called botulism and gas gangrene
13
Q
Clostridium tetani and Bacillus anthracis
A
- Tonic muscle spasm Spastic paralysis caused by tetanus and pulmonary anthrax
14
Q
Endospore resistance
A
- Extraordinary resistance to desiccation, heat, chemicals, and radiation in comparison to the vegetative bacteria
- Difficult to eliminate and can be used to test the efficacy of sterilisation methods
15
Q
Sterilisation
A
- Destroying all microbial life (including endospores)
- A sterile object is totally free of viable microorganisms
16
Q
Disinfection
A
- Reduces the number of pathogenic microorganisms (not endospores) to the point where they no longer cause diseases
- applied on inanimate objects (toxic to human tissue)
- Antiseptic can be applied to human tissue
17
Q
Sanitisation
A
Reduces the microbes to safe levels by public health standards
18
Q
Antimicrobial chemotherapy
A
- Drug treatment for specific infections used
internally to SELECTIVELY kill or inhibit growth of microorganisms within host tissues, targeting a unique structure of the specific microbe
19
Q
Control of bacterial growth
A
- Different microbes have different resistance to distinct antimicrobial control measures
- Prevent infection and spoilage
- Sterilisation process is the destruction of bacterial endospores, viruses and cellular organisms
- Processing of any product destined for parenteral
administration, or for contact with broken skin,
mucosal surfaces, or internal organs
20
Q
Most to least resistsant microorganism
A
- Pirons
- Endospores of bacteria
- Gram negative bacteria
- fungi
- virus without envolope
- gram positive bacteria
- Virus with lipid envolope
21
Q
Rate of microbial death
A
- Death of the whole population is not instantaneous:
- Death continues in a logarithmic manner as the time or concentration is increased.
22
Q
Effectiveness of the control agents depends on
A
- Time of exposure
- Microbial characteristics
- Number of microbes
- Environment (organic matter, temperature, biofilms)
23
Q
Effects on the microbes
A
- Alternation of membrane permeability
- Protein denaturation
- Damage to nucleic acids
24
Q
Physical treatments to control microbial death
A
- Temperature
- Heat (moist and dry)
- Cold temperatures
- Filtration
- Radiations
- Osmotic pressure
25
Q
Chemical treatments to control microbial death
A
- Alcohols
- Halogens
- Iodine
- Chlorine
- Phenolics
- Aldehydes
- Quaternary ammonium compounds
- Sterilizing gases
- Heavy metals
26
Q
Temperature effects on microbes
A
- Increased temperature kills microbes
- Moist heat more effective than dry heat
- Boiling does not destroy endospores and does not sterilise
27
Q
Moist heat effect on microbes
A
- Hot water, boiling water, or steam between 60°C and 135°C (autoclave, pasteurisation). Kills microbes by denaturating their proteins
28
Q
Dry heat effect on microbes
A
- Hot air or an open flame (Bunsen Burner, incineration), which ranges from 160°C to thousands of degrees Celsius. Kills microbes by dehydrating the
cell, and oxidation effects
29
Q
Autoclave
A
- Preferred sterilisation method, unless material is damaged by heat, moisture, or high pressure
- Closed chamber with hot saturated steam under pressure 121.5 C for 15 minutes, to sterilise
microbes/endospores pirons need more time - Steam must be in direct contact
30
Q
Pasteurisation
A
- Uses moist heat disinfection prevent the spoilage of beverages reduces spoillage of milk and beer
