Bacteriology Flashcards
What are the size comparison for bacteria compared to viruses and human cells?
Viruses are the smallest, then bacteria and then human cells being the largest
What is the study of fungi called?
Mycology
Can fungi manufacture their own food/ What is this called?
No, called heterotrophs
What are three key features of fungi:
Composed of filaments called hyphae
Have cell walls composed of chitin
Don’t have flagella
How is lysine synthesis carried out in fungi?
AAA Pathway- Amino Adipic Acid pathway
What is the fungal cell wall composed of?
Beta-1,3 and B-1,6 linked glucans
Chitin
What is the cell membrane made of in fungi and plants?
Plants- Sitosterol
Fungi- Ergosterol
What do fungi produce as a means of reproduction both sexually and asexually?
Spores
Give four commercial products fungal cells can produce due to their metabolic pathways:
-Ethanol
-Organic acids
-Enzymes
-Antibiotics
Describe Protozoa:
Eukaryotes- like animals don’t have cell wall
Heterotrophic (doesn’t produce own food)
Specialised vacuole for food digestion and water elimination
Reproduction both (a)sexually
What is a bacteriophage?
A virus that can infect a bacteria
What is the cell wall of bacteria made of?
Peptidoglycan
What are thylakoids and are they found in bacteria?
Yes, flattened discs with light sensitive pigment molecules
What is the size of a eukaryote and a prokaryote?
E= 2-200µm
P= 0.5- 2µm
What are the size difference between the size of ribosomes in eukaryotes and prokaryotes?
P= 70s
E= 80s
What are two different parameters used to measure the growth of bacteria?
Measure cell numbers
Measure cell mass
Describe the measurement of cell numbers to determine bacteria growth:
-Direct microscopic counts, using counting chambers
-Use electronic counting chambers but not often used for bacteria
-Indirect viable cell count, plate bacteria on culture of a nutrient agar surface and incubate
Form a colony over night, each colony is called an CFU (colony forming unit) and the number of CFUs is related to the viable number of bacteria on sample
Give disadvantages of measuring cell numbers to determine bacteria growth:
Microscopic counting- they are very small and can’t be distinguished if they are dead or living
Indirect- Takes some time as need to incubate over night
Describe the measurement of cell mass to determine bacteria growth:
-Direct measure physically of dry/ wet weight of after centrifugation
-Direct measure chemically of some chemical components
-Indirect measure of chemical activity e.g rate of O2 production/ consumption
-Turbidity measurements- determine the amount of light scattered by a suspension of cells compare it to a standard via a calibration curve
Describe a growth curve for bacteria:
Log of viable cells on y axis
Time on x axis
Lag phase- nothing happening, bacteria adjust to surroundings
Exponential- really rapid growth
Stationary- Equilibrium where cells dividing and cells dying
Death- Once nutrients run out, cells dying
What is an aerobe tolerant bacteria?
Doesn’t need O2 to survive but can tolerate it
What is a psychrophile?
Low temperatures, -5 and 15ºC
What is a mesophile?
10- 45ºC
What is a not homophile?
Most bacteria in this
Survives in salt conditions of 2.5% conc and under
Describe how bacteria cells replicate:
Binary fission
The DNA replicates, the replicating DNA molecules attached to the plasma membrane, as cell elongates the chromosomes are pulled apart
When cell is twice its original size, plasma membrane grows inward and cell wall forms between two cells
What is the difference between binary fission and mitosis?
A spindle is not utilised in BF
Describe conjugation as a form of genetic recombination in bacteria:
A cell with DNA called F (fertility) factor, F+, is able to replicate and transfer a copy of its DNA to another cell without F factor through a tube called a sex pilus
The sex pilus usually breaks off before the entire DNA from the donor cell is transferred
The DNA that is transferred issued to replicate similar genes in the recipient cell
State and describe 4 ways in how bacteria can change their genetic information:
- Transformation- bacterium picks up DNA fragments released by dead bacteria or secreted by live bacteria
- Transduction- bacteriophages carry portions of bacteria DNA from one cell to another
- Mutation- source of variation
- Resistance- against antibiotics can be transferred by transfer of plasmid
What are endospores?
Method of survival, not reproduction
Endospores are DNA and a portion of cytoplasm encased in a tough cell wall, they are resistant to extremes in temp, drying and harsh chemicals
Spores can endure for hundreds of years
What is an auxotroph?
Organism that needs lots of different nutrients, specific
What is a prototroph?
Only needs one organic substance
Name a way to differentiate between Gram -ve and Gram +ve bacteria:
Dyes
What is the difference between Gram -ve and Gram +ve bacteria?
Gram -ve, low amount of peptidoglycan, not sensitive against penicillin but sensitive against mechanical pressure
Gram +ve, high amount of peptidoglycan, sensitive against penicillin but not sensitive against mechanical pressure
Describe the features of peptidoglycan:
A polysaccharide component and peptide component
Polysaccharide consists of alternating N-acetlyglucosamin (NAG) and N- acetylmuramic acid (NAM) monosaccharides
Polysaccharide chain joined by short polypeptide chains
Polypeptides always attached to the NAM
What is the periplasmic space in bacteria?
Filled with enzymes
What does penicillin inhibit in bacteria?
The last step of peptidoglycan synthesis, the transpeptidation reaction
Transpeptidation is required to cross link the peptide side chains of the polysaccharide backbone
Penicillin binds to transpeptidase, they enzyme responsible for transpedidation
Why is it harder to kill Gram -ve bacteria?
Have outermsmbrane which is difficult to pass through
Have periplamsic space where the drug could possibly be hydrolysed so bacteria will survive
What are endotoxins and how do they work?
Endotoxins from Gram -ve bacteria are most common types of toxic reactions, result in contamination with pyrogens
They are lipopolysaccharides so pyrogenic activity is much higher than other pyrogenic substances
What are the physiological effects of pyrogens?
Depends on dose and route of admin:
If via the mouth then not as harmful as blood stream
If low dose than asymptomatic inflammatory response
If moderate dose than fever and changes in plasma composition
Describe the BP test for pyrogens:
Three rabbits at dose no greater than 10ml/kg
Rabbits housed carefully in controlled conditions and temp is monitored rectally before and at 30 mins intervals for 3 hours post admin
What are the limitations of the BP test for pyrogens?
Pyrogen tolerance
Biological variation
Unsuitable for many drug classes
Describe the BP test for bacterial endotoxins:
LAL test- based on endotoxin induced coagulation of the blood of the horseshoe crab
Test is based on the observation that the crab blood forms clots when exposed to endotoxins 1000x more sensitive than test for pyrons
What are the limitations of the BP test for bacterial endotoxins?
Certain chemicals can inhibit the interaction between the LAL sub and endotoxin
Can’t easily be used on viscous products
Only detect endotoxins produced by Gram -ve bacteria
What is depyrogenation?
Rinsing or diluting with pyrogenic rinsing fluid
For glassware: dry heat sterilisation; 650ºC - 1 min
250ºC - 45 mins
180ºC 4 hours
Removal of pyrogens from water by distillation (more reliable) and reverse osmosis
Why is depyrogenation difficult?
Pyrogens can often be difficult to remove from solution due to high variability of molecular weight
Also relatively thermally stable and insensitive to pH changes
