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Basic knowledge Flashcards

1
Q

What are microbial biofilms?

A

These are microorganisms that grow on surfaces, they are surface adhered. These are encassed by protecive matrix of sugars - anchoring them.

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2
Q

What is quorum sensing?

A

Process of cell-to-cell signaling and communication which can aid in regulating their genes in a coordinated manner.

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3
Q

Basic mechanism of a virus

A

Viruses are acellular and lack metabolic mechanisms to replicate themselves. They attack host cell and hijack its machinery for replication to occur.

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4
Q

What is metabolism?

A

The sum of all chemical reactions that take place within body/cell including anabolism and catabolism.

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5
Q

What is taxonomy?

A

The classification of organisms in an ordered system that indicates natural relationships – allows us to come up with a universal nomenclature.

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6
Q

What are the three shapes in bacterial morphology?

A

Cocci, Bacilli and Spirilium.

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7
Q

What is an opportunistic pathogen?

A

Commensal organisms that cause disease within immune suppressed patients.

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8
Q

What is a parasite?

A

Organisms that live in close association with another form of life - can be detrimental to the host.

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9
Q

What are commensal bacteria?

A

Harmless bacteria in a stable mutualistic relationship with human host.

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10
Q

What is the advantage of being a small size in bacteria?

A

Nutrients get in and waste products can get out of cells easily allowing for accelerated metabolism and thus growth. Small cells = large sa to volume ratio = the higher the rate of exchange of nutrients.

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11
Q

What is the bacterial cytoplasmic membrane made of?

A

Composed of phospholipid and protein molecules (40:60)

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12
Q

Describe the main function of bacterial plasma membrane.

A

The plasma membrane is a selectively permeable membrane, controlling the osmosis, diffusion and active transport.

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13
Q

Describe 5 (out of 7) other functions of plasma membrane, other than exchange.

A
  1. Transport systems such as E-flux pumps for active transport that use ATP to pump material in/out of cell
  2. For the ETS in respiration
  3. Cell wall synthesis with specialised molecules called bactoprenols which transports monomers which form cell wall from cytoplasm, through plasma membrane to the periplasmic space where cell wall is created.
  4. For flagella and pili attachment which are both attached to plasma membrane.
  5. Cell division.
  6. Site of waste removal.
  7. Involved in formation of endospores
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14
Q

What are inclusion granules and what are they made of?

A

These are storage granules made when nutrients are in excess and to be used when nutrients are limited. These are made of carbon, nitrogen, sulphur or phosphorus.

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15
Q

What are carboxysomes?

A

Play a role in bacterial photosynthesis. Carboxysomes are sites of CO2 fixation.

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16
Q

What are the functions of gas vacuoles?

A

These are gas bubbles found in aquatic photosynthetic bacteria which allows organism to control its density, allowing organism to rise and fall as needed to maintain optimum light levels.

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17
Q

What are endospores?

A

An endospore is an extremely resistant dormant cell structure produced by some bacterial species.
These allow bacteria to survive in harsh environmental conditions.

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18
Q

What is a glycocalyx and what 2 morphologies are formed?

A

Glycocalyx is a viscous layer surrounding a bacterial cell.

  1. Capsule - an extensive, tightly bound layer of gelatinous material adhered to cell wall (outside).
  2. Slime layer - Loosely attached and unorganised glycocalyx which surrounds cell.
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19
Q

Describe properties and functions of capsule/glycocalyx layer.

A

The immune system is able to detect glycocalyx - confers immunological specificity.

  1. Acts as osmotic buffer
  2. Facilitates adherence to surfaces and aids colonisation.
  3. Aids biofilm formation - prevents removal.
  4. Helps bacteria resist phagocytosis - capsule increases size of bacterial cell thus, phagocytes unable to engulf large cell.
  5. If engulfed by phagocyte, capsule prevents enzymatic attack of cell.
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20
Q

Describe flagella.

A

Flagella consist of single, coiled tube of protein called flagellin.
The ATP-dependent rotation of flagella propels bacterium through liquid medium by AT and allows for locomotion.
Flagella also allows cell-to-cell contact and ability to sense surfaces. May trigger biofilms.

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21
Q

Describe pili.

A

Pili are fine, filamentous structures that extend from bacterial cell surfaces.
These are found mainly in G-.
They are rigid immobile structures which originate from cytoplasmic membrane via basal bodies in cell wall.

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22
Q

Describe the pilus shaft.

A

Pilus shaft composed of helical monomers of protein pilin.
At end of shaft, is an adhesive tip which corresponds to shape of specific glycoprotein receptors on host cell.
- Allows bacterial cell to be attached to host.

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23
Q

Name and explain the 2 types of pili.

A
  1. Short attachment pili - aka short fimbriae = organelles of adhesion which allow bacteria to colonise environmental surfaces and prevent electrostatic repulsion.
  2. Long conjugation pili - aka F/sex pili = enable conjugation which is the transfer of DNA from a donor/male bacterium with a sex pilus to recipient/female bacterium to enable genetic recombination/genetic exchange.
    Key method to transmit plasmids containing genes conferring some advantageous characteristic.
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24
Q

Name 4 methods of genetic exchange/recombination.

A 
The transferred donor DNA can then be combined into the recipient's nucleoid by 4 mechanisms. 
Transformation
Transduction 
Conjugation
Transposition
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25
Explain process of transformation.
The process by which FREE DNA released from one cell is taken up by another cell. G+ cells, capable of taking up free DNA = competent cells. Short DNA fragments (from autolysis of bacterium) bind to DNA binding proteins on surface of competent recipient cells.
26
Explain what happens during transformation (Hint: role of enzymes)
Nuclease enzymes can cut the bound DNA into short fragments. One strand destroyed and the other penetrates into the bacterium. DNA fragment from donor is exchanged for DNA from recipient.
27
Explain process of transduction.
Transduction is the transfer of fragments of DNA from one bacterium to another by a bacteriophage-bacterial virus. 1. The phage DNA is inserted into the bacterial cell. 2. Early mRNA and protein synthesis occurs, DNA replication, viral components synthesis. 3. Assembly of phage component within bacterial cell. 4. Lysis of cell and release of new bacteriophage progeny. 5. New phage can inject this DNA into another bacterial cell. This DNA can be incorporated into gene of new bacteria.
28
What is binary fission?
Binary fission is the process by which prokaryotic cells divide and reproduce
29
Define the generation time.
The generation time is the time taken for a population to double. (Not an individual cell to split). When one cell divides into two = 1 generation has occurred.
30
What is geometric progression?
Geometric progression is the way in which bacteria increase their numbers by doubling every generation time only under optimal conditions.
31
What is batch culture and why can't exponential growth be obtained?
Batch culture is culture grown in an enclosed vessel. Exponential growth cannot be sustained as nutrient availability decreases and waste products from metabolism accumulates and thus inhibits growth.
32
Explain what happens during lag phase.
No increase in cell numbers but size of cells increase. Cells prepare for cell division - takes up nutrients, metabolic processes, macromolecular synthesis. The duration of lag phase depends on what stage the inoculum was taken from.
33
Explain what happens during exponential/log phase.
Binary fission occurs at maximal rate due to optimal conditions reached. No of cells increases as an exponential function of 2n (geo progression). Growth is balanced. Rate and duration of log phase determined by environmental factors.
34
Explain what happens during stationary phase.
Growth rate decreases. No exp growth. Growth is restricted by nutrient exhaustion or metabolic waste accumulation. Unbalanced growth - cells have different compositions to log phase cells because those cells are experiencing the most severe nutrient limitation and will begin to metabolise non-essential proteins/organelles, cells will then have a diff composition to log phase cells. Growth rate = death rate (cryptic growth)
35
Explain what happens during death phase.
Rate of heath is higher than rate of growth. Cells are surviving by using up non-essential cellular contents. Cell lysis occurs releasing intracellular contents into the media.
36
Describe the formation of endospores.
The developmental process is initiated in response to nutrient deprivation. Allows bacterium to produce a dormant and high resistant cell to preserve the cell's genetic material in times of stress. Spores are highly differentiated and differ from mother cell. Endospores are not a reproductive structure but rather a survival form.
37
What environments can spores survive in?
Areas of severe nutrient depletion, heat, radiation, areas with chemicals.
38
What are SASPs and what is their function?
These are small acid soluble proteins made during process of sporulation. Functions: 1. They bind tightly to DNA in the core, protecting from UV damage, heat and desiccation. 2. Change the molecular structure of DNA from the normal Beta form to more compact Alpha form. 3. Acts as carbon source for outgrowth of new vegetative cell during germination.
39
What is the function of calcium dipocolinate?
Functions to reduce water availability within core and helps keep core dehydrated. The complexes intercolate i.e. insert between bases of DNA and so adds to the stability of DNA.
40
What feature of spore allows for resistance?
Dehydrated core and impermeability of spore coat.
41
What is a function of the cortex?
Cortex may osmotically remove water from the core aiding dehydration.
42
Describe process of conversion from spore to vegetative cell.
Involves activation, germination and outgrowth. 1. Activation - occurs by removing stress inducer, triggered by specific nutrient or triggered by sublethal heating. 2. Germination - during this loss of resistance properties occurs with loss of calcium dipocolinate and cortex components. 3. Outgrowth - involves water uptake and synthesis of new RNA, proteins and DNA. Vegetative cell then emerges from fractured spore coat.
43
What is the liquid component of the cytoplasm called?
Cytosol
44
What is the function of cytoplasm?
It is the site of most bacterial metabolism including anabolic and catabolic reactions.
45
Bacteria secrete endoenzymes and exoenzymes. What is the definition of both?
Exoenzymes - Extracellular enzymes - secreted by cell and functions outside he cell. Endoenzymes - Intracellular enzymes - secreted by cell and functions side the cell.
46
Describe composition of cytoplasm.
80% water. Nucleic acids, enzymes, amino acids, carbs, lipids, ions etc found in cytoplasm Cytosol
47
Describe basic structure of DNA within bacterial cell.
DNA is double stranded and supercoiled.
48
What is the function of ribosomes?
It is the site of protein synthesis.
49
What are plasmids?
Plasmids are small circular molecules of extrachromosomal DNA. They are independent of normal chromosome - don't divide at the same time. Contain between 5-100 genes.
50
What is the advantage of having plasmids?
Plasmids can contain advantageous genes not expressed in normal chromosome e.g. virulence, antibacterial resistance etc.
51
What is the glycocalyx? Describe the structure of the capsule and slime layer.
Glycocalyx is a viscous covering surrounding a cell made of polysaccharide/polypeptide slime. Capsule - Extensive, tightly bound accumulation of gelatinous material adhering to cell wall. Slime - Unorganised and loosely attached layer
52
Name the 3 basic parts of flagellum.
Filament Hook Basal body
53
Pili Fact
Pili can switch their adhesive tips in order to adhere to different types of cells and evade immune defences.
54
Describe the structure of phospholipids.
Phospholipids contain a polar phosphate molecule attached to a 3 carbon glycerol backbone. Two fatty acid chains dangling from the carbons of glycerol. Hydrophilic layer = glycerol and phosphate Hydrophobic layer = fatty acids
55
Name the 3 basic transporter proteins.
Uniporter Antiporter Symporter
56
What are uniporters?
Transport proteins that transport a substance from one side of the membrane to the other. Transport is down concentration gradient - does not require metabolic energy - powered by potential energy of gradient.
57
What are antiporters?
Transport proteins that transport one substance across the membrane in one direction while simultaneously transporting a second substance across the membrane in the opposite direction. Energy by ATP (active transport) and Proton Motive Force (PMF)
58
What is Proton Motive Force (PMF)?
PMF is an energy gradient resulting from the movement of hydrogen ions (protons) from high concentration to low concentration.
59
What are symporters?
Transport proteins that simultaneously transport two substances across the membrane in the same direction. Energy from ATP (active transport) and PMF.
60
Group translocation is an active transport process exclusive to bacteria. Describe the process.
A substance is transported across the membrane via a transporter protein. The substance is chemically altered during its transport. Once inside the membrane, the plasma membrane becomes impermeable to that modified substance, thus trapping it within the cell.
61
Describe the effects of disinfectant on cytoplasmic membrane.
Disinfectants cause an alteration of bonds in cytoplasmic membrane causing pores to form - can allow leakage of cellular contents.
62
Outer membranes are found in Gram- cells. Describe the composition of outer membrane.
It is a lipid bilayer composed of phospholipids, lipoproteins, proteins and lipopolysaccharides (LPS)
63
What is the main function of lipoproteins?
Connects the outer membrane to the peptidoglycan layer.
64
What two parts is LPS composed of?
Lipid A and polysaccharide chain
65
Describe Lipid A in LPS. | Describe the polysaccharide chain in LPS.
Lipid A is a derivative of 2N-acetyl glucosamine (NAG) with 7 fatty acids connected to it. The conserved core polysaccharide is attached to lipid A containing heptose, glucose and glucosamine sugars. The rest of the polysaccharide contains repeating sugars called O-Antigen.
66
Porins are found on the outer membrane. Define them.
Porins are proteins that form pores in the outer membrane wide enough to allow small hydrophilic molecules to pass through.
67
What is the function of the outer membrane?
Acts as a diffusional barrier. Is semi-permeable allowing entry of some substances, retention of enzymes and prevention of some substances. (Explains why G- bacteria are less susceptible to antibiotics than G+)
68
Define codon.
A series of three consecutive mRNA nucleotide bases coding for a specific amino acid.
69
From what 2 ways can genetic variation arise?
Mutation | Gene transfer
70
Define mutation.
A mutation is an error during DNA replication which results in a change of the sequence of deoxyribonucleotide bases in DNA.
71
What is spontaneous mutation? How is it caused?
This is a mutation which occurs naturally (every one in million/billion divisions). Caused by a low level of natural mutagens in the environment.
72
What is induced mutation?
Mutation caused by mutagens - substances that cause a higher rate of mutation.
73
Genetic recombination is defined as the transfer of DNA from one organism to another with subsequent integration into the DNA of the recipient. This can occur through horizontal transmission and vertical transmission. Define both.
Vertical transmission - The transfer of DNA from one generation to the next. Horizontal transmission - The transfer of DNA between bacteria of the same generation.
74
Why genetic exchange is important in bacteria?
This is the way in which bacteria get selective advantage from the host.
75
What happens during process of conjugation involving F plasmids?
1. F+ cell has an F plasmid coding for a sex pilus. 2. The sex pilus adheres to F- cell, The sex pilus retracts and a bridge is created between the two bacteria. 3. One strand of F+ plasmid breaks and enters recipient bacteria while one strand remains in the donor. 4. Both bacteria make a complementary strand of F+ plasmid and now both bacteria are F+, capable of producing a sex pilus.
76
Describe process of transposition.
Transposable elements/transposons move from one DNA site to another within the genome of the same organism. - moves DNA from one location to another.

Microbiology (6 decks)

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