Bacteriology Flashcards
Types of replication- what is another term for DNA transfer/ acquisition?
Horizontal DNA transfer (conjugation, transformation, transduction)
2 living cells picking up dead cell molecules - DNA, acquire new material
Types of replication - what is another term for binary fission?
Vertical DNA transfer
Parent cell - mother cell
Resultant - daughter
Parent to offspring
Outline the steps of Binary fission
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)
When is binary fission required?
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
What is the definition of binary fission?
The ability of prokaryotes to double in mass before dividing
What is FTs?
It is a family of bacterial proteins that are structural analogues of the eukaryote tubulin
(Filamentous temperature sensitive mutans)
FTsK and FTsZ
Where does site specific recombination occur?
FTs ring
What is the self checking mechanism used to inhibit unwanted separation in binary fission?
MinC D and E
What is the transforming principle?
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)
What is transduction?
There is a transfer of DNA between bacterial cells where a bacteriophage is the transfer agent
- specialised
- generalised
What is a bacteriophage?
DNA viruses surrounded by a protein coat, various shapes and sizes
E.g. The e.coli phage - T4
What sometimes goes wrong with bacteriophages?
They inject their DNA and use the host machinery to reproduce this sometimes goes wrong
What is specialised transduction?
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
What is generalised transduction?
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)
What is a plasmid?
Conjugation- fertility factor which allows the transfer of DNA to cells of the same species- unidirectional
Donor - F+
Recipient - F-
What facilitates conjugation?
Pili
What is the process of conjugation?
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
What form spores?
Gram positive cells , SpoIII E- protein, resistant to stresses
What is the protein ring around a spore called?
Forespore - protoplast
What is the name of the very outer layer of the spore?
Exosporium
What is the morphology of endospores?
Location - terminal sub terminal central
Shape - circular, ellipsoid
Spore diameter compared to cell diameter- non deforming and deforming
What does a spore have that a vegetative cell does not have?
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)
What is special about the exposporium?
It has many enzymes that provides the slight metabolism that the spore has (outside layer that is in contact with the environment)
When do spores become active ?
Give an example?
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
What is cleaning?
Removal of contamination but does not necessarily destroy microorganisms - pre requisit before infection or sterilisation
As organic material inactivated disinfectants
What is disinfection?
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
What is sterilisation?
Complete destruction of all microorganisms including spores - accomplished by physical or chemical methods
What is antisepsis?
Destruction of microorganisms existing in their vegetative state on living tissue
What is decontamination?
Preferred term in microbiological labs for demurring materials safe for use or disposal
What are the factors that influence the ability to kill microbes? (6)
Strength, time, temperature (rate of microbe death doubles with every 10degrees rise in temperature), type, number, environment around the area to be decontaminated
What are the examples of heat sterilisation?
Dry heat, wet heat, incineration
What is autoclaving?
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
What is the problem with indicators used after sterilisation?
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
What are examples of other sterilisation methods that do not require heat?
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
What is the difference between irradiation non ionising and ionizing?
Non - UV
Ionizing- Gamma (electromagnetic Rays), or electron beams (particulate)
What are examples of chemical sterilisation?
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)
What is CJD?
Creutzfeld Jakob disease (transmissible spongiform encephalopathies)
Prions
Mad cow disease
Iatrogenic CJD- patients accidentally infected by the doctor
