Endospores and Control of microbial growth

Question 1

What are Endospores?

Answer 1

Resting/dormant/inert form of some bacterial cells
Produced only by two Gram+ Genera: Bacillus and Clostridium

Question 2

What are the environmental conditions that would be lethal for the bacteria? (mechanism of survival)

Answer 2

e.g. nutrients depletion,
environmental stresses (extreme temperature, pH),
chemical stresses (antibiotics, disinfectants), etc

Question 3

Resistance of endospores and period of survival?

Answer 3

Extraordinarily resistant to desiccation, heat, chemicals, and radiation

survive for long periods (up to centuries)

Question 4

Sporulation:

Answer 4

endospore formation

production of many new structures, enzymes, and metabolites along with the disappearance of many vegetative cell components

Question 5

Germination:

Answer 5

endospore returns to vegetative state

Question 6

Ensospores are NOT a form of _______

Answer 6

reproduction
only 1 new cell germinates from each endospore

Question 7

Sporulation is a process of differentiation; when does it start?

Answer 7

when growth ceases due to lack of nutrients or environmental stress
= activating a set of genes to induce this differentiation and quenching genes involved in the germinative life of bacteria

Question 8

Describe the endospore structure?
can you draw it ? (slide 7 lec 3 microbiology)

Answer 8

ovoid shape and multi-layered cthat contians;

A CORE= dehydrated and metabolically inactive)
containing DNA, ribosomes, essential proteins and large depots of calcium dipicolinate (Ca-DPA)

Question 9

What are the layers surrounding the core?

Answer 9

3-4 coating layers
- core walls (innermost)
-cortex (made of peptidoglycan)
- spore coat (fairly thick, impermeable - resistance to chemicals and antibiotics)
- exosporium (thin covering - not always present)

Question 10

Germination - full detailed definition

Answer 10

Process of an endospore that revert back to a vegetative cell very rapidly (even after decades), through removal of the stress inducer

requires = activation step (heating to damage spore coat; reversible)

core in hydrated = spore coats are cracked and cell metabolism is restored

Question 11

What are the 3 steps of germination?

Answer 11

1) activation
2) initation
3) outgrowth

Question 12

What diseases can form from spore forming bacteria?

Answer 12

Clostridium botulinum – botulism [ Flaccid paralysis - muscle weakness]

Clostridium perfingens – gas gangrene

Clostridium tetani – tetanus [Spastic paralysis - two muscle spasms]

Bacillus anthracis – cutaneous or pulmonary anthrax

Question 13

Why is endospores resistance to heat, chemical and radiation (compared to vegetative bacteria) an advantage?

Answer 13

make endospores difficult to eliminate - resistant to most common disinfection procedures

issues a clinical setting or in aseptic situations - used to TEST efficacy of sterilisation methods

Question 14

What are the 4 points of control bacteria growth?

Answer 14

1) sterilisation
2) disinfection
3) sanitisation
4) antimicrobial chemotherapy

Question 15

1) sterilisation

Answer 15

Destroying all microbial life (including endospores)
A sterile object is totally free of viable microorganisms

Question 16

2) disinfection

Answer 16

Reduces the number of pathogenic microorganisms (not endospores) to the point where they no longer cause diseases

Disinfectant: agents applied on inanimate objects/surfaces (toxic to human tissue)

Antiseptic: agents applied on living tissue

Question 17

3) sanitisation

Answer 17

reduces the microbes to safe levels by public health standards

Question 18

4) antimicrobial chemotherapy

Answer 18

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

Question 19

Different microbes have ________ resistance to distinct antimicrobial control measure

Answer 19

different

Question 20

What is the main goal of sterilisation?

Answer 20

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

Question 21

important - Most resistant to least resistant

Answer 21

Prions
Endospores of bacteria
Mycobacteria
Cysts of bacteria
Vegetative bacteria
Gram - bacteria
Fungi, most fungal spores
Viruses w/o envelopes
Gram + bacteria
Viruses w lipid envelopes

Question 22

What is the rate of microbial death?

Answer 22

Death of the whole population is not instantaneous:

logarithmic manner as the time or concentration is ^^^

Question 23

Treatments to control the microbial death = what does effectiveness of control agents depend on?

Answer 23

1. Time of exposure
2. Microbial characteristics
3. Number of microbes
4. Environment (organic matter, temperature, biofilms)

Question 24

Treatments to control the microbial death =
Effects on the microbes

Answer 24

1. Alternation of membrane permeability
2. Protein denaturation
3. Damage to nucleic acids

Question 25

Treatments to control the microbial death
= TWO types

Answer 25

1) Physical
2) Chemical

Question 26

Physical treatments to control microbial death

Answer 26

Temperature
Heat (moist and dry)
Cold temperatures
Filtration
Radiations
Osmotic pressure

Question 27

Chemical treatments to control microbial death

Answer 27

Alcohols
Halogens
Iodine
Chlorine
Phenolics
Aldehydes
Quaternary ammonium compounds
Sterilizing gases
Heavy metals

Question 27

Chemical treatments to control microbial death

Answer 27

Alcohols
Halogens
Iodine
Chlorine
Phenolics
Aldehydes
Quaternary ammonium compounds
Sterilizing gases
Heavy metals

Question 28

How does heat affect microbes

Answer 28

Elevated temperatures (> Max temp.) = kill microbes

Moist heat = hot/boiling/steam [60C = 135C] autoclave, pasteurisation). Kills microbes by denaturating their proteins

Dry heat = hot air/ oen flame [bunsen burner] 160C to thousandsC, Kills microbes by dehydrating the cell, and oxidation effects

Question 29

Is Moist or dry heat most effective?

Answer 29

Moist heat

Question 30

Boiling does not destroy endospores and not _______

Answer 30

sterilise

Question 31

Moist heat = Autoclave
121C fro 15 mins to sterilise microbes/endospores

Answer 31

preferred sterilisation method, unless material is damaged by heat, moisture, or high pressure

Closed chamber with hot saturated steam under pressure

Steam must directly contact material

Strips containing harmless endospores are used as quality control

Question 32

Moist heat = Pasteurisation

Answer 32

disinfection

reduce microbes responsible for spoilage of beer, milk, wine, juices etc.

Question 33

Except for ____, Pasteurisation does not sterilise!

Answer 33

UHT (ultra high temperature processing)***

Question 34

What are the 3 methods of Pasteurisation?

Answer 34

1. Classic Method of Pasteurisation: 65 o C for 30 minutes
2. Flash Pasteurisation (HTST): Used today. 72 o C for 15 seconds
3. Ultra High Temperature Pasteurisation (UHT): 140 o C for 4 seconds and then cooled quickly in a vacuum chamber. This is a sterilising method

Question 35

Cold – Low temperatures
4-8C - used for food preservation

Answer 35

slow down microbial growth

Reduces metabolic rate of most microbes to stop their proliferation and toxin production, but often do not kill microbes

Question 36

Freezing temperature (<0o C)
what temp is solutions in glycerol?

Answer 36

70C

used for long-term storage and preservation of some bacterial cultures (useful for analysis)

Question 37

What is filtration? How does it work?

Answer 37

Removal of microbes by passage of a liquid or gases through membrane material with defined small pores (< microbe size)

Solution with microbes is sucked through the layer under vacuum and microbes are retained

Question 38

What is filtration used in?
sizes of bacteria?

Answer 38

heat sensitive materials (vaccines, enzymes, antibiotics)
Pore size for most bacteria: 0.2-0.45 μm
Pore size for viruses: 0.01 μm

Air filtration using high efficiency particulate air (HEPA) filters in laminar flow biological safety cabinets (0.3 μm)

Question 39

Osmotic pressure:

Answer 39

The use of high concentrations of salts and sugars in foods is used to increase the osmotic pressure and create a hypertonic environment.

Question 40

Plasmolysis

Answer 40

As water leaves the cell, plasma membrane shrinks away from cell wall. Cell may not die, but usually stops growing.