Microbiology 3

Question 1

Endospores

Answer 1

• Resting form of some bacterial cells
• Produced only by two Gram+ Genera e.g. Bacillus and Clostridium

Question 2

Funtion of endpores

Answer 2

• 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

Question 3

Sporulation

Answer 3

• 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

Question 4

Germination

Answer 4

• When endospores return to its vegitative state

Question 5

Endospore structure

Answer 5

• Ovoid shape and a multi-layered structure

Question 6

1st layer

Core walls

Answer 6

• Innermost later Core containing DNA, ribosomes, essential proteins and large depots of calcium dipicolinate

Question 7

2nd layer

Cortex

Answer 7

made of peptidoglycan

Question 8

3rd layer

Spore coat

Answer 8

• fairly thick, and impermeable layer.
• It confers resistance to chemicals/antibiotics

Question 9

4th layer

Exosporium

Answer 9

Thin covering, not always present

Question 10

Germination

Answer 10

• 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

Question 11

3 steps of germination

Answer 11

• Activation
• Initiation
• Outgrowth

Question 12

Clostridium botulinum and Clostridium perfingens

Answer 12

• Causes flaccid paralysis muscle weakness called botulism and gas gangrene

Question 13

Clostridium tetani and Bacillus anthracis

Answer 13

• Tonic muscle spasm Spastic paralysis caused by tetanus and pulmonary anthrax

Question 14

Endospore resistance

Answer 14

• 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

Question 15

Sterilisation

Answer 15

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

Question 16

Disinfection

Answer 16

• 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

Question 17

Sanitisation

Answer 17

Reduces the microbes to safe levels by public health standards

Question 18

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

Control of bacterial growth

Answer 19

• 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

Question 20

Most to least resistsant microorganism

Answer 20

• Pirons
• Endospores of bacteria
• Gram negative bacteria
• fungi
• virus without envolope
• gram positive bacteria
• Virus with lipid envolope

Question 21

Rate of microbial death

Answer 21

• Death of the whole population is not instantaneous:
• Death continues in a logarithmic manner as the time or concentration is increased.

Question 22

Effectiveness of the control agents depends on

Answer 22

• Time of exposure
• Microbial characteristics
• Number of microbes
• Environment (organic matter, temperature, biofilms)

Question 23

Effects on the microbes

Answer 23

• Alternation of membrane permeability
• Protein denaturation
• Damage to nucleic acids

Question 24

Physical treatments to control microbial death

Answer 24

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

Question 25

Chemical treatments to control microbial death

Answer 25

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

Question 26

Temperature effects on microbes

Answer 26

• Increased temperature kills microbes
• Moist heat more effective than dry heat
• Boiling does not destroy endospores and does not sterilise

Question 27

Moist heat effect on microbes

Answer 27

• Hot water, boiling water, or steam between 60°C and 135°C (autoclave, pasteurisation). Kills microbes by denaturating their proteins

Question 28

Dry heat effect on microbes

Answer 28

• 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

Question 29

Autoclave

Answer 29

• 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

Question 30

Pasteurisation

Answer 30

• Uses moist heat disinfection prevent the spoilage of beverages reduces spoillage of milk and beer