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CMBM Exam 3: Immunology > Intro to Bacteria > Flashcards

Intro to Bacteria Flashcards

1
Q

Describe the following differences between Eukaryotic and Prokaryotic cells: Major groups, size, nucleus, chromosome, membrane bound organelles ribosomes, cytoplasmic membrane, cell wall, respiration, and reproduction.

A

Eukaryotes Prokaryotes
Major Groups: Fungi/Parasites Bacteria
Size: >5um 0.5-3um
Nucleus: classic membrane no membrane
Chromosome: >1, strands, diploid ~1, circular, haploid
MBO: Present Absent
Ribosomes: 80S (60+40) 70S (50+30)
CM: Contains sterols Anionic polymers
Cell Wall: Fungi (chitin) Peptidoglycan
Respiration: Mitochondria Cytoplasmic memb.
Reproduction: Sexual/asexual Binary fission (asexual)

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2
Q

What are 5 macroscopic characteristics of microbes that we can use to distinguish?

A
  1. Size
  2. Shape
  3. Fermentation of sugars
  4. Hemolysis
  5. Resistance to antibiotics
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3
Q

What are 4 microscopic characteristics of microbes that we can use to distinguish?

A
  1. Size
  2. Shape
  3. Arrangement
  4. Staining characteristics
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4
Q

What are 3 basic shapes of bacteria?

A
  1. Coccus (circular)
  2. Bacillus (rod)
  3. Spirillum (spiral)
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5
Q

Upon gram staining what color are gram negative and gram positive bacteria?

A

Gram negative: Pink

Gram positive: Purple

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6
Q

What bacteria cannot be classified by gram staining and why?

A
  1. Mycobacterium: waxy outer coat; acid fast
  2. Mycoplasma: no peptidoglycan
  3. Chlamydia: spore-like structure
  4. Treponema: very thin
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7
Q

What are 3 metabolic distinctions that can be made?

A
  1. Oxygen requirement
  2. Substrate utilization (lactose or non-lactose fermenter)
  3. Production of specific enzymes (ie catalase)
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8
Q

What is the most precise way of distinguishing between different microbes?

A

Genetic testing/Gene sequencing
Highly conserved sequences (16S rRNA) identify the genus
Highly variable sequences identify and species or subspecies

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9
Q

How does transcription and translation differ between eurkaryotes and prokaryotes

A

In prokaryotes transcription and translation may be coupled

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10
Q

What are the 5 functions of the prokaryotic cell membrane?

A
  1. Electron transport/ATP production
  2. Uptake and Secretion (ie toxins)
  3. Maintenance of membrane potential
  4. Septum formation for cell division
  5. Site of DNA and cell synthesis
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11
Q

What is the main purpose of the cell wall in prokaryotes?

A
  1. To prevent osmotic lysis of the plasma membrane
  2. Protect the cell from drying and desiccation
  3. Determine and maintain the shape of the cell
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12
Q

What is the structure of peptidoglycan?

A

Alternating and repeating disaccharide units of NAG and NAM which form a linear polymer in which the NAG is bound to a 4 amino acid oligopeptide of Ala-Glu-Lys-Ala. The polymers are then crosslinked by a pentaglycine which connects the Lys on one polymer to the Ala on another.

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13
Q

How does lysozyme disrupt the peptidoglycan structure?

A

Lysozyme cleaves the beta-1,4 glycosidic bond between NAG and NAM

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14
Q

How does penicillin function?

A

Penicillin binds to the transpeptidase which cross links the polysaccharides of the peptidoglycan wall by catalyzing the Ala-Ala cleavage during peptidoglycan crosslinking. The result is a deficient cell wall which causes swelling/osmotic lysis of the bacterium

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15
Q

Aside from peptidoglycan, what other components are found composing the cell wall?

A

Lipoteichoic acid and Teichoic acid

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16
Q

S. aureus is a gram positive bacteria that is particularly resistant to harsh conditions and can survive for a longer time than other bacteria. How does it achieve this at the molecular level?

A

There is an extra layer of cross linking that creates a more rigid cell wall

17
Q

What is teichoic acid (TA) and lipoteichoic acid (LTA)? What is special about LTA?

A

TA is a polymer of glycerol or ribitol phosphate that is covalently attached to peptidoglycan
LTA is a polyglycerol phosphate that is covalently linked to glycolipids in the cytoplasmic membrane
LTA is antigenic with different serotypes existing and promotes adherence to mammalian cells

18
Q

What 2 important components is the outer membrane of gram negative bacteria composed of?

A

Lipopolysaccharide (LPS) and Porin proteins

19
Q

What 4 main things are found in the periplasmic space of gram negative bacteria?

A
  1. Thin layer of peptidoglycan with very little cross linking
  2. Hydrolytic enzymes (breakdown macromolecules)
  3. Binding proteins for uptake of metabolites
  4. Virulence factors (collagenases, proteases, hyaluronidases, and antibiotic resistance enzymes)
20
Q

How does LPS function when it elicits an immune response?

A

As an endotoxin

21
Q

How does the outer membrane of gram negative bacteria function to help the cell?

A

It is a barrier to…

  1. Lysozyme
  2. Antibiotics
  3. Harsh environments
    * Only small hydrophilic molecules can pass through the porins, certain antibiotics like vancomycin cannot enter
22
Q

What are the 4 components (starting with the distal end) of LPS? Give a brief description of each

A
  1. O antigen: Variable repetitive glycan polymer which antibody is directed against
  2. Core polysaccharide: highly conserved
  3. Disaccharide diphosphate
  4. Lipid A: Toxic portion which is recognized by TLR4
23
Q

Name 5 specialized bacterial structures

A
  1. Capsule
  2. Biofilm
  3. Flagella
  4. Fimbriae (Pili)
  5. Spores (Endospores)
24
Q

What is a capsule composed of and what are some of its functions?

A

Made of polysaccharide (peptides in bacillus)
Functions to protect the bacteria from phagocytosis as well as promote adherence to tissues, prosthetic devices, and protect against drying

25
Q

Define biofilm

A

Aggregate of bacteria that bind to each other on a surface within a slime layer

26
Q

What is the slime layer of a biofilm composed of?

A

It is an extrapolymeric substance composed of

  1. Polysaccharide
  2. DNA
  3. Protein
27
Q

What is the purpose of flagella and how are they recognized by the immune system?

A

They are long helical protein filaments that endow the bacteria with motility.
They are recognized by TLRs

28
Q

What are fimbriae composed of and what function do they serve?

A

They are hair-like structures composed of pilin which cover the surface of the bacterium
Purpose to to mediate specific binding to target cells and are often required to cause an infection. The adhesive component is found at the tip of the pili

29
Q

What are spores?

A

Dormant structures formed by vegetative gram (+) bacteria in response to environmental stress which makes them resistant to heat, drying, freezing, and disinfectants for long periods of time

30
Q

How are different spores classified?

A

The location of the spore within a cell is characteristic of the bacteria and helps to identify them

31
Q

In order of least to greatest, what 3 bacterial metabolic processes produce the most energy?

A
  1. Fermentation
  2. Anaerobic respiration (terminal electron acceptor such as nitrate, sulfate, CO2)
  3. Aerobic respiration
32
Q

What is the time it takes for a bacterium to divide?

A

Doubling Time or

Generation Time

33
Q

What are the 4 phases of bacterial growth and what are some features associated with each phase?

A
  1. Lag: little change in cell number but increased metabolic activity
  2. Exponential (Log): Divide as fastest possible rate
  3. Stationary: No change in cell number/equilibrium between cell division and death. Nutrients are exhausted and waste builds and pH rises (increased NH3 due to deamination of amino acids)
  4. Death: death rate exceeds the growth rate
34
Q

What are 7 factors that affect bacterial growth?

A
  1. Carbon source
  2. Nitrogen for protein synthesis
  3. Iron required for enzyme (electron transport)
  4. pH
  5. Temperature (clinically relevant bacteria grow at 37 degrees)
  6. Osmotic conditions (salt concentration)
  7. Oxygen concentration
35
Q

What are 6 classifications of bacteria based on tolerance to oxygen?

A
  1. Obligate aerobes (require oxygen)
  2. Obligate anaerobes (die in presence of oxygen)
  3. Facultative anaerobes (prefer oxygen but can live without it)
  4. Aerotolerant anaerobes (do not use oxygen but are not harmed by it)
  5. Microaerophilic (require oxygen, do not ferment, but are harmed by high levels of oxygen)
  6. Capnophilic (grow in a CO2 enhanced environment)
36
Q

What allows certain bacteria to live in the presence of oxygen?

A
  1. Superoxide dismutase (required): reduces superoxide anion to molecular oxygen and hydrogen peroxide
  2. Peroxidase: Reduces hydrogen peroxide to 2 H2O
  3. Catalase: Combines 2 H2O2 to produce 2 H2O and 1 O2
    * Must have SOD and either or both peroxidase and catalase

CMBM Exam 3: Immunology (21 decks)

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