Bacteriology

Question 0

Types of replication- what is another term for DNA transfer/ acquisition?

Answer 0

Horizontal DNA transfer (conjugation, transformation, transduction)
2 living cells picking up dead cell molecules - DNA, acquire new material

Question 1

Types of replication - what is another term for binary fission?

Answer 1

Vertical DNA transfer
Parent cell - mother cell
Resultant - daughter
Parent to offspring

Question 2

Outline the steps of Binary fission

Answer 2

Doubling of DNA within the cell, DNA molecule is physically anchored to the cell wall of chromosome
Reproducing cytoplasmic material
Via cascade reaction - DNA on opposite ends of the cell - split (membrane pinching)

Question 3

When is binary fission required?

Answer 3

It is required for cell replication and involves the bacterial chromosome

• the chromosome is anchored to the cell membrane
• replication of the DNA occurs at the same time as membrane replication

Question 4

What is the definition of binary fission?

Answer 4

The ability of prokaryotes to double in mass before dividing

Question 5

What is FTs?

Answer 5

It is a family of bacterial proteins that are structural analogues of the eukaryote tubulin
(Filamentous temperature sensitive mutans)
FTsK and FTsZ

Question 6

Where does site specific recombination occur?

Answer 6

FTs ring

Question 7

What is the self checking mechanism used to inhibit unwanted separation in binary fission?

Answer 7

MinC D and E

Question 8

What is the transforming principle?

Answer 8

Discovered in S.pneumoniae
Smooth - polysaccharide coats
Rough to not, the cell membrane prevents contact with antibodies
If you kill the smooth and incubate with rough, the rough will become smooth cells - indicates an uptake of genes (DNA)

Question 9

What is transduction?

Answer 9

There is a transfer of DNA between bacterial cells where a bacteriophage is the transfer agent

• specialised
• generalised

Question 10

What is a bacteriophage?

Answer 10

DNA viruses surrounded by a protein coat, various shapes and sizes
E.g. The e.coli phage - T4

Question 11

What sometimes goes wrong with bacteriophages?

Answer 11

They inject their DNA and use the host machinery to reproduce this sometimes goes wrong

Question 12

What is specialised transduction?

Answer 12

Lytic cycle- Viral DNA is incorporated into the host DNA as normal but when there is excision of the viral DNA from the host DNA - takes genes adjacent from the site of lysogeny and incorporates them into the viral genome - extremely efficient but selective and transfers only a small region of the bacterial chromosome- forms defective phage that can then transduce

Question 13

What is generalised transduction?

Answer 13

Allows the transfer of any gene from one bacterium to the other - but at low frequency (therefore not just those adjacent to the site of lysogeny)
- used to make chromosomal alterations to the target host species
E.g. P1 phage of E.coli (biotech purposes)

Question 14

What is a plasmid?

Answer 14

Conjugation- fertility factor which allows the transfer of DNA to cells of the same species- unidirectional
Donor - F+
Recipient - F-

Question 15

What facilitates conjugation?

Answer 15

Pili

Question 16

What is the process of conjugation?

Answer 16

F+ produces a pilus coded for by the F plasmid
Attaches to F-
For,a bridge between cytoplasms
F+ uses ribosomes to copy the plasmid, copy is transferred through pilus, the F- then becomes F+ male
1- the donor cell is sharing one of the copies with the recipient (reproduces all plasmids)
2- linking of 2 cytoplasms (can have R plasmids that code for antibiotic resistance)
3- spikes fibriae - pilus is a type of fibriae

Question 17

What form spores?

Answer 17

Gram positive cells , SpoIII E- protein, resistant to stresses

Question 18

What is the protein ring around a spore called?

Answer 18

Forespore - protoplast

Question 19

What is the name of the very outer layer of the spore?

Answer 19

Exosporium

Question 20

What is the morphology of endospores?

Answer 20

Location - terminal sub terminal central
Shape - circular, ellipsoid
Spore diameter compared to cell diameter- non deforming and deforming

Question 21

What does a spore have that a vegetative cell does not have?

Answer 21

High heat radiation and chemical resistance 
Metabolism low 
mRNA content is low 
Lysozyme sensitivity - none 
Calcium dipicolinate- high 
% water of cell volume - 10-20 
PH - 5.7
(Properties of bacillus subtilis spore)

Question 22

What is special about the exposporium?

Answer 22

It has many enzymes that provides the slight metabolism that the spore has (outside layer that is in contact with the environment)

Question 23

When do spores become active ?

Give an example?

Answer 23

When the stress is removed spores are activated and then germinate into vegetative cells
E.g. B.megaterium germinate in the presence of glucose or L-alanine and such germination is stimulated when sores are heated before incubation with these substrates

Question 24

What is cleaning?

Answer 24

Removal of contamination but does not necessarily destroy microorganisms - pre requisit before infection or sterilisation
As organic material inactivated disinfectants

Question 25

What is disinfection?

Answer 25

Destruction of vegetative organisms that might cause disease or in context of food ind. cause spoilage
It usually employs chemical and does not necessarily kill spores

Question 26

What is sterilisation?

Answer 26

Complete destruction of all microorganisms including spores - accomplished by physical or chemical methods

Question 27

What is antisepsis?

Answer 27

Destruction of microorganisms existing in their vegetative state on living tissue

Question 28

What is decontamination?

Answer 28

Preferred term in microbiological labs for demurring materials safe for use or disposal

Question 29

What are the factors that influence the ability to kill microbes? (6)

Answer 29

Strength, time, temperature (rate of microbe death doubles with every 10degrees rise in temperature), type, number, environment around the area to be decontaminated

Question 30

What are the examples of heat sterilisation?

Answer 30

Dry heat, wet heat, incineration

Question 31

What is autoclaving?

Answer 31

Steam penetration (wet heat) 
Best results if air is excluded 
Correct cycle and hold times - 121 degrees at 15 psi for 15 mins 
Or 121 degrees at 30 psi for 3 mins 
E.g. Hospital sheets

Question 32

What is the problem with indicators used after sterilisation?

Answer 32

They are all based on chemical reactions modelling organism growth - but will take time to grow bacterial and check if killed - therefore it is not perfect

Question 33

What are examples of other sterilisation methods that do not require heat?

Answer 33

Filtration, sonic and ultrasonic vibrations (burst membrane), irradiation
Note - UV Rays are used to mutate proteins and sterilise the surface but can’t penetrate plastic etc. Therefore gamma rays are better but expensive

Question 34

What is the difference between irradiation non ionising and ionizing?

Answer 34

Non - UV

Ionizing- Gamma (electromagnetic Rays), or electron beams (particulate)

Question 35

What are examples of chemical sterilisation?

Answer 35

Depends on spectrum and compatibility
Halogens, alcohols (Ethanol and isopropanol), cetrimide QAC, chlorohexane- skin and mucous membranes antiseptic aureus (can support growth of gram negative- aeruginosa)

Question 36

What is CJD?

Answer 36

Creutzfeld Jakob disease (transmissible spongiform encephalopathies)
Prions
Mad cow disease
Iatrogenic CJD- patients accidentally infected by the doctor