Lecture 2: Microbiological concepts with a focus on bacteria

Question 1

Prokaryotic cells:

a) Name 2 prokaryotic microrganisms
b) are they larger or smaller than eukaryotic cells?
c) Do they have a nucleus or a nuclear membrane?
d) what is their DNA like?
e) do they have membrane structures?
f) do they have a cell wall? If yes what does it contain?
g) do they have larger or smaller ribosomes than eukaryotic cells?

Answer 1

a) eubacteria and archaea
b) much smaller (0.1 um - 10 um)
c) they don’t have a nucleus or a nuclear membrane
d) their DNA is unenclosed but similar in structure to eukaryotes
e) do not have membrane structures
f) they have a complex cell wall containing peptidoglycan (expect the mycoplasma species don’t)
g) smaller ribsomes

Question 2

Eukaryotic cells:

a) Name 5 eukaryotic micorganisms
b) are they larger or smaller than prokaryotic cells?
c) Do they have a nucleus or a nuclear membrane?
d) what is their DNA like?
e) do they have membrane structures?
f) do they have a cell wall?
g) do they have larger or smaller ribosomes than prokaryotic cells?

Answer 2

a) Plants, animals, algae, fungi, protozoa
b) Larger 10-100 µm
c) have both nuclear membrane and nucleus
d) DNA inside nucleus and same DNA structure as ProkC
e) Membrane structures present
f) Plants, fungi & algae have simple cell walls (animals & protazoa do not)
g) Larger ribosomes (80s)

Question 3

Study the structure of prokaryotic cell

a) name its 8 common structures.
b) do all prokaryotes have all these structure?
c) name two structure ALL prokaryotes have.

Answer 3

a) nucleiod region, ribosomes, plasma membrane, cell wall, capsule, prokaryotic flagella, fimbriae & pili
b) Not every bacteria has all of these structures
c) they will DNA floating around and a plasma membrane.

Question 4

a) What is the function of the prokaryotic plasma membrane?
b) Is the cell wall and plasma membrane permeable or impermeable?
c) what is the function of the prokaryotic flagella?
d) what are the hair like structures of prokaryotes called and what is their function?
e) how does having this hair like structure affect our ability to get rid of the bacteria.

Answer 4

a) allows the movement of nutrients, wastes and signalling molecules in and out of the cell
b) Both the plasma membrane and cell wall are permeable
c) Flagella rotates to allow the bacteria to move.
d) the hair like structures are called fimbriae, the main function of which is to allow attachement.
e) The bacteria with fimbriae are harder to get rid of than bacteria w/o fimbriae

Question 5

Important differences between prokaryotes and eukaryotes:

a) which one contains the membrane-bound organelles such as mitochondria and golgi apparatus?
b) which one has the cell wall that contains peptidoglycans?
c) There is an exception to question b, what is this exception?

Answer 5

a) Only eukaryotes contain, membrane-bounded organelles.
b) only prokaryotes have peptidoglycans in cell wall
c) EXCEPT, peptidoglycan is only found in the Bacteria/Eubacteria domain. Achaeans have simpler cell walls without peptidoglycan.

Question 6

Cellular reproduction: Eukaryotes vs Prokaryotes

a) which one reproduces by binary fission?
c) which one reproduces by mitosis/ meiosis?

Answer 6

a) prokaryotes

b) eukaryotes

Question 7

Important differences between prokaryotes and eukaryotes:

a) which one produces endospores?
b) are endospores the same as fungal spores? If not how are they different to fungal spores?

Answer 7

a) prokaryotes only
b) Endospores are not the same as fungal spores.
- Endospores are a survival mechanism for certain bacteria where as in fungi spore as for reproduction

Question 8

Important differences between prokaryotes and eukaryotes:

a) which one can specialise and form tissue?
b) which one never changes?

Answer 8

a) eukaryotes

b) prokaryotes

Question 9

Bacterial cell structures:

a) Where is the DNA/ chromosomes located?
b) where are the ribosomes located?
c) what is cytoplasm?
d) do all bacteria have capsules?
f) how do bacterial capsules affect us? Explain why.
g) do bacilli and cocci have similar structure?

Answer 9

a) Chromosomes (DNA) are located centrally
b) Ribosomes are scattered throughout the cytoplasm
c) Cytoplasm= liquid filled space inside the cell
d) Not all bacteria have capsules
e) The ones with the capsule are MORE pathogenic because capsules provide better adherence to host cells and thus it is harder for the immune system to get rid of
f) bacilli and cocci have the same structure except of course their shape, and both may or may not have capsules.

Question 10

Bacteria Intracellular Materials:

a) What does the nuclear material contain and what is its purpose?
b) does it have a nucleus or nuclear membrane?
c) what are plasmids? and what is their function?
d) Plasmids are transferable between bacteria, explain what this is important.
e) what is the function of ribsomes?

Answer 10

a) includes the double stranded circular DNA which is the bacteria’s genetic control centre
b) no nuclear membrane = no nucleus
c) Plasmids: Small, closed, circular pieces of DNA
separate from the main DNA. These code for
non-essential functions e.g. Antibiotic resistance
d) transferring copies of plasmids is how bacteria transfer resistance between cells
e) proteins synthesis

Question 11

Bacterial cytoplasm:

a) what is it composed of?
b) what type of reactions occur here?
c) What else happens in the cytoplasm?
d) what does it contain?

Answer 11

a) 80% composed of fluid and a complex of chemicals
b) enzymatic rxns for energy production
c) Also where all the cellular biosynthesis happens (protein production at ribosomes)
d) it contains all of the intracellular materials

Question 12

Bacterial cell wall:

a) for those bacteria that have a cell wall (which most of them do), what does the cell wall provide?
b) Is the cell wall permeable or impermeable?
c) what kind of substances does the cell wall secrete of the cell?
d) What role does the cell wall play in Gram staining?

Answer 12

a) the cell wall provides rigidity and strength and thus helps the cell keep its shape it also provides protection.
b) Just like the membrane inside the cell wall, the cell wall also has to be permeable to substances to allow waste to go out and nutrients to come in
c) -secretes toxins out
- secretes enzymes out
- inter cell signals in/out
d) The structure of the bacterial cell wall is how we get the gram stain results of Gram +ve and Gram -ve as the cell wall composition between gram +ve and gram -ve bacteria differs.

Question 13

Cell wall composition:

a) what is the main difference in the cell wall of Gram positive and Gram negative bacteria?
b) what determines if a cell is G.pos or G.neg?
c) what are the colours for gram pos and gram neg?

Answer 13

a) The main difference between Gram +ve and Gram -ve bacteria is the peptidoglycan layer
b) the amount of peptidoglycan in a cell wall that determines whether bacteria is gram +ve or gram -ve
c) G.pos= blueish purple colour
- G.neg= pink

Question 14

Gram positive bacteria:

a) Is the peptidoglycan layer thick or thin?
b) how are the peptidoglycan layers held together?
c) do they have an outer membrane layer?

Answer 14

a) thick
b) vertically running through the peptidoglycans are teichoic acid and lipoteichoic acid and these hold the peptidoglycan layers together.
c) no they do not have an outer membrane layer, that is exclusive to Gram pos bacteria only.

Question 15

Gram negative bacteria:

a) Is the peptidoglycan layer thick or thin?
b) do Gram neg bacteria have an outer membrane?

Answer 15

a) Thin layer of peptidoglycan

b) they have an outer membrane which is a lipopolysaccharide

Question 16

Gram stain:

a) what is Gram type/ Gram reaction?
b) what microorganism is Gram stain used for?
c) what are the gram stain’s result based on?
d) describe the colour and cell wall of Gram pos
e) describe the colour and cell wall of Gram neg
f) what are gram variables?
g) how should you report your gram stain results?
h) how are the results abbreviated?

Answer 16

a) staining reaction
b) gram stains are used JUST for bacteria and bacteria ONLY.
c) the results are based on the cell wall composition of bacteria.
d) purple colour, large amount of peptidoglycan in cell wall
e) pink colour, small amount of peptidoglycan in cell wall
f) bacteria that stain as both purple and pink.
g) report results as: Gram Pos or Gram Neg, Bacilli or Cocci (always capitalize the G!)
h) often abbreviated to GPB, GPC, GNB, GNC

Question 17

Method of gram staining:

What colour do G. Pos and G. neg bacteria start out as?

Answer 17

colourless.

Question 18

Assume your bacteria has already been smeared on your slides:

a) what is the 1st step in gram staining.
b) does this step kill the bacteria?
c) what colour are your G. pos & G. neg bacteria in this step?

Answer 18

a) Heat fixation: to stick the bacteria to the glass slide so that they don’t wash off.
b) no bacterial is still alive and viable
c) colourless

Question 19

Assume your bacteria has already been smeared on your slides:

a) What is the 2nd step in Gram staining?
b) what is the duration of this step?
c) what colour are your G. pos & G. neg bacteria in this step?

Answer 19

a) Crystal violet
b) leave for about 30 secs
c) purple

Question 20

Assume your bacteria has already been smeared on your slides:

a) what is the 3rd step in Gram staining?
b) what is the duration of the step
c) what colour are your G. pos & G. neg bacteria in this step?

Answer 20

a) Iodine treatment
b) leave for about 30 secs
c) purper (lighter)

Question 21

a) What is the chemistry behind step 3?
b) How does this affect Gram. Pos bacteria?
c) How does this affect Gram. Neg bacteria?
d) what fundamental difference does this result in?

Answer 21

a) the crystal violet and Lugol’s iodine molecules combine to make a larger molecule inside bacteria
b) In Gram-positive bacteria, once we wash the slide with the alcohol in the next step, those two molecules combined cannot wash out back through that peptidoglycan, they are too large.
c) In Gram-negative bacteria, that thin layer of peptidoglycan is not sufficient enough to hold these molecules inside the cell and they wash out.
d) And that is the fundamental reason for their colour difference

Question 22

a) What is the fourth step in Gram staining?
b) what is the duration of the step
c) what colour are your G. pos & ; G. neg bacteria in this step?

Answer 22

a) decolourization using Alcohol or Acetone
b) for Alcohol wash for 15 secs, for acetone wash for 1 sec
c) Gram pos: purple, Gram neg: colourless
* gram pos still have the crystal violet + iodine complex inside them

Question 23

a) What is the fifth step in Gram staining?
b) what is the duration of the step
c) what colour are your G. pos & G. neg bacteria in this step?

Answer 23

a) counter stain (safranin): using carbol fushin
b) leave for about 30 seconds
c) GP= purple, GN= pink!

Question 24

a) What bacteria is the most commonly isolated bacterial cause of diarrhoea, particularly in western countries?
b) where is this bacteria found?
c) how does it spread?
d) is it Gram neg or Gram pos?
e) is it Bacilli or cocci?
f) what is a special feature about their shape?

Answer 24

a) Campylobacter
b) Found in raw chicken and animal faeces.
c) Spreads mainly through kids putting their hands in the environment and then in their mouth
d) Gram neg
e) Bacilli
f) the bacilli has a curve in them giving it helical shape that resembles a cartoon seagull.

Question 25

a) what is glycocalyx?

b) Name its two types.

Answer 25

a) a gelatinous material which coats the surface of some bacteria
b) capsules & slime layers

Question 26

Glycocalyx: capsules

a) what is a capsule’s organisation like?
b) what is its attachment like?
c) what is its function?
d) Some bacteria are typed by their capsule composition. Explain this using an example.

Answer 26

a) Highly organised
b) firmly attached
c) protect against phagocytosis
d) Haemophilus influenzae B – Hib
- the B represents the capsule type- the composition of its capsule is unique compared to other kinds of the same organism.

Question 27

Glycocalyx: Slime

a) what is its organisation like?
b) what is its attachment like?
c) what is its function?
d) How can we remove slime?

Answer 27

a) not highly organised
b) not firmly attached
c) helps bacteria slide on surface and protects it from drying
d) easily washed off with water

Question 28

a) What are Capsules and Slime made up of?

b) how does having a glycocalyx affect the virulence of bacteria?

Answer 28

a) Both of these are made up of polypeptides (chains AA) and/or polysaccharides (sugar molecules/carbohydrates)
b) bacteria with glycocalyces are often more pathogenic because they have better adherence and they help protect from phagocytosis
- some even provide protection from antibiotics (still being researched)

Question 29

a) are capsules permeable?

b) can they absorb stains?

Answer 29

a) capsules are permeable
b) but they cannot absorb stain because the polysaccharide and polypeptide composition of the capsule doesn’t stain in the Gram stain, it remains colourless.

Question 30

Bacterial projections: Fimbriae

a) what is fimbriae?
b) how many are present in a bacterial cell?
c) what is their function?

Answer 30

a) Fimbriae are bristle like short projections.
b) they are present in multiple numbers
c) function is ADHERENCE: not only can they adhere to host tissues, but they can pretty much adhere to anything be it tissue, glass or plastic.

Question 31

Bacterial projections: Pili

a) what is Pili?
b) how many are present in a bacterial cell?
c) what is their function?

Answer 31

a) bristle like long projections
b) present singly or in pairs
c) function: adherence to another bacterium during DNA transfer and conjugation (bacterial sex).

Question 32

Conjugation:

a) Pili can also be referred to?
b) what does pilli do?
c) how does Pili attach to recipient cell?
d) what gets copied inside the host DNA during conjugation?
e) how does this copy pass to recipient cell?
f) what do both the donor and recipient end up with?
g) what does this encode for?
h) how does your answer to f spread?

Answer 32

a) pili can also be referred to sex pili/F pili
b) Pass plasmids (circular piece of extra chromosomal DNA) from one bacteria to another
c) pili extends out of the host DNA and attaches to the recipient cell
d) the plasmid gets copied inside the host DNA
e) it unwraps from circular shape and travels down the pili into recipient cell
f) both the donor and the recipient end up with the same plasmid (donor doesn’t lose its plasmid if it passes it to the recipient).
g) Plasmid DNA may encode for antibiotic resistance
h) Plasmids can be passed between dissimilar bacteria which is hpw antibiotic resistance spread.

Question 33

Bacterial cell projections: Polar distributions of Flagella

a) what is the function of flagella?
b) what is monotrichous flagella?
c) what is lophotrichous flagella?
d) what is amphitrichous flagella?
e) what is peritrichous fagella?

Answer 33

a) Flagella’s function is motility ONLY
b) Monotrichous is the simplest -one single flagella on one end
c) Lophotrichous has many flagella on one end
d) Amphitrichous has many on either end
e) Peritrichous has random flagella distribution all around the cell.

Question 34

Bacterial endospores:

a) what is sporulation?
b) what is sporulation for?
c) name the two spore (endospore) forming genera of bacteria?
d) what are endospores resistant to?
e) how long can they survive?
f) when does a spore change back to a bacterium?

Answer 34

a) sporulation is a process in which some bacteria can make a copy of their DNA with some cytoplasm and enclose it in layers of thick protein
b) It is for survival under unfavourable growth conditions (low moisture or low nutrients)
c) Bacillus and Clostridium
d) Endospores are resistant to heat and disinfectants
e) survive for years in soil/dust
f) They we only go from being a spore back into a bacterium once the outside environment becomes favourable again.
* one spore regenerates into one vegetative cell when it regenerates.

Question 35

How do Bacteria grow?

a) how do bacteria reproduce and what is this process called?
b) what occurs during this process?

Answer 35

a) Reproduce by an asexual process called binary fission
b) Single cell splits into two identical daughter cells
- Chromosome duplicates
- and same genetic material in both daughter cells

Question 36

How do Bacteria grow?

c) what is generation time?
d) is generation time the same for all bacteria?
e) what does generation time depend on? explain this by giving examples.

Answer 36

c) Generation time- how long it takes to double cell numbers
d) it is not the same for all bacteria, it varies with organism: 15-20 minutes to 24 hours, or longer
e) Depends on environmental conditions & location
- in vitro (in laboratory) maybe faster
- in vivo (in human body) maybe slower
- e.g. Escherichia coli takes 15-20 min in broth solution in lab. vs. 12-24 hrs in GIT

Question 37

a) During binary fission what happens in each cell division?

b) what does this result in?

Answer 37

a) the number of bacterial cell doubles with each cycle.
b) This results in very rapid increase in bacterial population. Overnight, this process can will results in millions of bacterial cells

Question 38

The Bacterial Growth Curve – in broth solution
a) what happens in the bacterial lag phase?
(3 points)

Answer 38

1. Initial lag phase: bacteria is responding to the change in environment e.g. the nutrients in the broth solution
2. Bacteria is processing the nutrients in terms of their composition e.g. aa nutrients vs carbohydrate nutrients and it will then switch on and produce the appropriate enzyme to digest those nutrients
3. The lag phase is also when the DNA replication of the bacteria occurs.

Question 39

The Bacterial Growth Curve – in broth solution

a) what happens in the bacterial exponential phase?

Answer 39

a) Exponential phase: all of a sudden the bacterial population takes off, because now they are all switched on and with binary fission, the population goes bananas.

Question 40

The Bacterial Growth Curve – in broth solution

a) what happens in the bacterial stationary phase?

Answer 40

a) Stationary phase: the amount of reproduction= the amount of death
b)

Question 41

The Bacterial Growth Curve – in broth solution:

a) what are the four phases of the bacterial growth curve?

Answer 41

1. lag phase
2. exponential phase
3. stationary phase
4. death/ decline phase

Question 42

The Bacterial Growth Curve – in broth solution

a) what happens in the bacterial death/ decline phase?

Answer 42

a) Death or decline phase: if we don’t add any more nutrients and we let the stationary phase continue, eventually the amount of toxicity and waste products will outweigh the amount of nutrients that are left, and the bacteria would start to die

Question 43

Bacterial Colonies on agar: 18-24 hours growth

a) what is a colony?
b) why is streaking bacteria on agar important?
c) what does the colony morphology assist in?
d) on an agar plate what does a colony look like?
e) one cell grows how many colonies?
f) are all the cells in a colony different?
g) upto how many cells can a colony end up with

Answer 43

a) A colony is a ‘heaped pile’ of daughter progeny from ONE original bacterial cell that was inoculated onto an agar plate
b) Streaking enables us to see if our bacterial growth is pure or mixed
c) Colony morphology assists with identifying the actual type of bacteria
d) Colony= a single dot on an agar plate
e) One colony grows from one cell, thus streaking out 10 bacterial cells would grow 10 colonies.
f) All cells in a colony are identical
g) Each colony could end up with >10 to the power of 7 cells

Question 44

Various bacteria require and/or prefer particular growth environments/nutrients.

a) is this always the case for all bacteria?
b) how can bacteria the categorized?
c) how can we identify an unknown organism.

Answer 44

a) no, Sometimes these conditions are essential and sometimes these conditions are only preferred
b) Bacteria can be categorised based on their Growth requirements/preferences
c) Testing for these conditions can help to identify an unknown organism

Question 45

Atmospheric conditions/ preferences:

a) What are obligate aerobes?
b) What are microaerophiles?
c) What are obligate anaerobes?
d) What are facultative anaerobes
e) What are carboxyphiles (capnophiles)

Answer 45

a) Oxygen is essential for growth- Grow in air (78% Nitrogen, 21% Oxygen, 0.039% CO2????)
b) Requires low levels of O2 (must have some, 6-16%)
c) Unable to grow in O2 grow- Will only grow in the complete absence of O2
d) able to grow with or without O2 e.g. E. coli
e) Grows best with increase concentration of CO2 (2.5 to 5 to 10%)

Question 46

Temperature preferences:

a) what are Psychrophiles?
b) What are Psychrotrophs?
c) What are Mesophiles?
d) What are Thermophiles?

Answer 46

a) Psychrophiles: Growth temp. 0 to <20 degrees Celsius, optimum= 15 degrees Celsius
b) Psychrotrophs: Growth 0 to 40ºC, optimum= 20 to 30ºC
c) Mesophiles: Growth 10 to 45ºC, optimum= 37ºC (body temp)
d) Thermophiles: Growth 45 to 85ºC, optimum= 50 to 55ºC

Question 47

pH tolerance:

a) what does it apply to?
b) What are Acidophiles?
c) What are Alkalophiles?
d) What are Neutrophiles?

Answer 47

a) Applies to buffers and growth media
b) Acidophiles: prefer acidic pH , optimum pH 0-5.5
c) Alkalophiles: prefer basic pH, range pH 8.5-11.5
d) Neutrophiles- prefer close to neutral pH, optimum pH 7.2-7.6

Question 48

a) what is biochemistry?

b) what is the primary element needed in biochemistry?

Answer 48

a) chemistry of living organisms

b) carbon is the primary organism needed

Question 49

a) What is metabolism?
b) what two processes does metabolism utilize?
c) what are these processes?
d) are they exogernic or endogernic?

Answer 49

a) Metabolism is the sum of all chemical reactions
b) utilises 2 processes: catabolism and anabolism
c) Catabolism (decomposition): Breaking of chemical bonds–> larger molecules broken into smaller molecules
- Anabolism (biosynthesis): Creation of chemical bonds to form larger molecules from smaller molecules
c) catbolism releases enegery (exogernic) where as anabolism requires energy (endergonic)

Question 50

a) what do catabolism and anabolism need to be fueled by?
b) What is the name of the major biological energy storage molecule?
c) what does the utilization of energy involve?
d) what are catabolic and anbolic processes facilitated by?
e) what is this facilitator?
f) what does the facilitator do?

Answer 50

a) fueled by a supply of nutrients and energy
b) Adenosine triphosphate (ATP)
c) The utilisation of energy involves breaking ATP down into its precursors i.e. catabolism of ATP to release that energy for use
d) Catabolic and Anabolic processes are facilitated by enzymes
e) enzymes are biological molecules that act as catalysts for metabolic reactions
f) they greatly increase rate of reactions but are not consumed in reactions

Question 51

Energy Storage (ATP– adenosine triphosphate):

a) what is the breakdown and formation of ATP mediated by?
b) what happens does the formation and breakdown of ATP depend on?
c) what does catabolism of ATP do?
d) what does anabolism of ATP do?

Answer 51

a) The breakdown of ATP & formation of ATP is mediated by oxidation-reduction (Redox) rxns. These rxns are always coupled (can’t have one without the other).
b) formation & breakdown of ATP depends on the addition or removal of phosphate groups
c) Catabolism of ATP releases energy
d) Anabolism: Adding phosphate groups to AMP to produce ATP requires energy

Question 52

Carbohydrate Catabolism to get ATP:

a) what is the principle carbohydrate utilised in ATP production?
b) How do microbes/ bacteria obtain this carbohydrate? give a few examples.
c) what two pathways do microbes use to produce ATP?
d) give a brief description of both pathways.
f) both pathways start with a common pathway. What is this common step?

Answer 52

a) principle carbohydrate utilised for ATP production is glucose
b) Microbes have enzymes to break down larger sugars into glucose . e.g. of large sugars: mannitol, fructose, lactose, sorbitol, galactose
c) Microbes use cellular respiration (oxygen) or fermentation (no oxygen) to produce ATP
d) -Respiration produces lots of ATP and CO2 and H2O
- Fermentation produces low ATP & organic waste (acids, alcohols)
f) Both pathways start with glycolysis (Embden-Meyerhof-Parnas pathway), but follow different subsequent pathways

Question 53

STUDY GLYCOLYSIS, RESPIRATION AND FERMENTATION.

Answer 53

STUDY GLYCOLYSIS, RESPIRATION AND FERMENTATION.

Question 54

Host- Microbes relationship:

a) What is mutualism? give examples
b) what is commensalism?
c) what is parasitism? give example

Answer 54

a) Mutualism– Symbiotic relationship where both members benefit e.g. Gut flora including E. coli and Bifidobacterium sp.
b) Commensalism– Symbiotic relationship where one member benefits without affecting the other
c) Parasitism (amensalism or antagonism)- Relationship where one member benefits while the other is harmed e.g. viruses, pin worm, malaria, lice (pubic and head), syphilis, gonorrhoea

Question 55

Normal Flora (NF) (normal microbiota):

a) Humans & animals are colonised by microbes during & after birth. Where are these derived from?
b) is Normal flora harmful?
c) list four functions of normal flora.

Answer 55

a) derived from:
- Derived from birth canal and contact with environment
- Food and baby formula
- Hand to mouth from people, objects and air
b) No. Normal Flora are harmless microbes that have important roles in maintaining the health of the host i.e. they are beneficial
c) 1. NF occupy colonisation sites on tissue preventing access to foreign microbes
2. NF in the gut produce several B vitamins and Vit K
3. NF secrete chemicals that antagonise foreign microbes
4. Stimulate the developing immune system in children

Question 56

Normal flora:

a) does normal flora always remain the same.
b) What are the two kinds of normal flora?

Answer 56

a) No, NF is constantly changing throughout life

b) Resident flora (permanent) or transient flora (hours – months)

Question 57

what happens when we encounter a brand new microbe? (3 outcomes)

Answer 57

1. Cause disease
2. NF could antagonise the new microbe
3. Or it could become part of your NF (either for a short period or permanently)

Question 58

stages of infectious disease:

What are the five stages of infectious disease?

Answer 58

1. incubation period
2. prodromal phase
3. invasive phase
4. decline phase
5. convalescence

Question 59

stages of infectious disease: Incubation phase

a) Are there any symptoms?
b) What do the initial invading microbes do?
c) What must the microbes overcome?
d) What are the pathogenic organism assisted by?
e) If the host defenses are overcome what happens?

Answer 59

a) No symptoms
b) Initial invading microbe(s) colonise a body site(s)
c) Must overcome host defenses (immune system, skin, normal flora)
d) Pathogenic organisms are assisted by their virulence mechanisms
e) If host defenses overcome, the numbers of organisms increase

Question 60

stages of infectious disease:

a) what happens in prodromal phase?
b) what happens in invasive phase?
c) what happens in decline phase?
d) what happens in convalescence

Answer 60

a) Prodromal phase: Mild symptoms
b) Invasive phase- Identifiable disease with dramatic increase in microbes (may continue to death)
c) Decline phase- Reduction of microbes (immune response and/or treatment)
d) Convalescence (recovery)

Question 61

a) What are virulence factors?
b) does every strain of the same organism possess the same array of virulence factors?
c) what are the 4 things microbes produce during an infection that give them their virulence factors?

Answer 61

a) virulence factors are traits that collectively give the microbes the ability to cause disease
b) No, the same organism can either be capsulated or uncapsulated, the capsulated would be more virulent
c) microbes produce: toxins (includes the intoxication of food),
produce and release enzymes, produce haemolysins & also produce adherence factors (fimbriae, pili, glycocalyx)

Question 62

a) How does microbial production of toxins impact virulence?

b) what are the two types of toxins?

Answer 62

a) Toxins can kill host cells and cause vomiting and diarrhoea
b) Two types: Endotoxins and Exotoxins

Question 63

How does microbial production and secretion of enzymes impact virulence?

Answer 63

• : help to invade tissue (spreading factors)
  
  • : kill host cells
  • : evade immune system

Question 64

How does microbial production of haemolysins impact virulence?

Answer 64

They lyse the RBC in the lab on a blood agar plate but in the body they don’t specifically target the RBC, instead they are toxic to a variety of cells.

Question 65

How does microbial production of adherence factors impact virulence?

Answer 65

increase adherence of microbes via adherence factors such as fimbriae, pili, glycocalyx

Question 66

Endotoxins:

a) are these derived from gram neg or gram pos?
b) how are these released?

Answer 66

a) Endotoxins are derived from Gram -ve bacteria ONLY remember these have lipopolysaccharide (LPS) in their cell wall.
b) when the cell dies, the cell wall breaks up
- and the wall fragments containing LPS endotoxin is released.
- thus endotoxins are made up of some of the molecules of the cell wall.