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Microbiology > Medical Microbiology - Intro > Flashcards

Medical Microbiology - Intro Flashcards

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Biology 101 flashcards
1
Q

True or False: All living organisms use DNA as their genetic material?

A

True

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2
Q

What are the three major groups of organisms?

A

Eubacteria

Archaebacteria (Archaea)

Eukarya (Eukaryotes)

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3
Q

True or False: Archaea are closer to Eucaryotes on the Tree of Life than Eubacteria are.

A

True; Archaea are much closer, evolutionarily, to Eucaryotes than are Eubacteria.

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4
Q

True or False; Viruses are the smalles infectious particles?

A

True

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5
Q

What is the genetic material of viruses?

A

Most viruses contain either DNA OR RNA; they typically do not contain both.

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6
Q

What is the exception to the rule that viruses usually contain DNA or RNA?

A

Mimivirus is the exception. This virus contains DNA and RNA.

It is a virus of amoeba.

It contains genes for nucleotide and amino acid synthesis.

It does not, however, contain genes for ribosomes.

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7
Q

What is a prion?

A

Prions are small particles that are composed of abnormally-folded proteins.

They cause disease by causing other proteins within the body to misfold and clump together in aggregates (plaques).

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8
Q

What are the characteristics of Eukaryotes?

A

Membrane-bound organelles

DNA contained within a nucleous

Linear DNA contained within multiple chromosomes

~20,000 genes

No cell wall

Large size as compared to bacteria and viruses

80S ribosome made up of 40S subunit and 60S subunit

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9
Q

What are the characteristics of Eubacteria (Prokaryotes)?

A

Lack membrane-bound organelles

DNA contained within a nucleopid region

DNA is circular chromosome

May contain circular plasmids (DNA) as well

Usually only one plasmid

1000-6000 genes

Has cytoplasmic inclusions (granuels)

Usually live independently

Small size as compared to Eukaryotes

Contain a cell membrane AND a peptidoglycan cell wall (Most contain cell walls)

70S ribosome made up of 30S subunit and 50S subunit

Do not reproduce sexually

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10
Q

How are bacteria characterized?

A

Shape

Size

Spatial arrangement

Gram + or -

Pathogenecity

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11
Q

Describe fungi.

A

Fungi are eukaryotes

Most have a cell wall that is made of chitin

Some are single celled (yeasts) and some are multi-cellular (molds)

Some can switch between being single and multicellular (Dimorphic); this is frequently determined by temperature

Fungi can reproduce both sexually and asexually; fungi are frequently characterized by their mode of reproduction

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12
Q

Describe parasites.

A

Can be unicellular (protozoans) or multicellular (worms, insects)

Some are obligate parasites

Others may have a free-living stage

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13
Q

What is an obligate parasite?

A

This is an organism that cannot complete its lifecycle without exploiting a suitable host.

Without the host, the parasite will not reproduce.

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14
Q

What is the size range of most viruses?

A

0.03 to 0.3 um

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15
Q

What is the size range of most bacteria?

A

0.1 to 10 um

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16
Q

What is the size range of most protozoa and fungi?

A

4 - 10 um

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17
Q

What are the mechanisms of host defense?

A

The immune system.

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18
Q

What are the characteristics of viruses?

A

Viruses have DNA or RNA as their genetic material (One exception: Mimivirus has both)

Obligate, intracellular parasite

Cannot reproduce outside of the cell

Have no organelles

Have a protein coat (Capsid) that helps to protect them from the environment

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19
Q

How many major shapes of bacteria are there?

A

Three:

Rods

Spiral

Cocci

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20
Q

True or False; Bacteria usually live independently.

A

True; bacteria can live in ‘bioflims’ with other bacteria however.

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21
Q

What are the three major parts of the bacterial cell and what are their functions?

A

Cell membrane: Carries out many biochemical / enzymatic reactions, participates in cell division, involved in ATP production via the electron transport chain, contains the enzymes for cell wall production.

Cell wall: Made up of peptidoglycan

Capsule: Slime layer. Protective layer surrounding bacterial cell.

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22
Q

What is the bacterial cell wall?

A

The bacterial cell wall is a semi-rigid layer of peptidoglycan that is outside of the cell membrane.

It helps the bacteria maintain shape, protects against lysis, determines Gram staining characteristics, and is a target for some antibiotics.

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23
Q

What do the shapes and arrangements of bacteria result from?

A

The shapes and arrangements of bacteria result from the cell wall and cell division.

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24
Q

What are the smallest bacterial cell types?

A

Mycoplasma and spiroplasma

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25
Q

What is the bacterial cell wall made of?

A

It is made up of a peptidoglycan layer (Murein layer)

This is a polymer of N-acetylglucosamine (NAG, GluNAc) and N-acetylmuramic acid (NAM, MurNAc)

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26
Q

How is the bacterial cell wall held together?

A

It is held together by beta 1,4 linkages between NAM and NAG

Four amino acids also attach to NAM and these help to provide more stability.

One set of amino acids is cross-linked to another set. This leads some bacteria to have peptide bridges in the peptiodglycan cell layer and this is the target of penicillins.

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27
Q

What form of amino acids do bacteria use?

A

D form

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28
Q

Image of gram + and gram - cell walls.

A
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29
Q

Second image of gram + and gram - cell walls.

A
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30
Q

Third image of gram + and gram - cell walls.

A
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31
Q

What are the characteristics of Gram + bacteria?

A
  1. cytoplasmic lipid membrane
  2. thick peptidoglycan layer
  3. capsule polysaccharides (only in some species)
  4. flagellum (only in some species)
    • if present, it contains two rings for support as opposed to four in Gram-negative bacteria because Gram-positive bacteria have only one membrane layer.
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32
Q

What are the characteristics of Gram - bacteria?

A
  1. Cytoplasmic membrane
  2. Thin peptidoglycan layer (which is much thicker in gram-positive bacteria)
  3. Outer membrane containing lipopolysaccharide (LPS, which consists of lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet
  4. Porins exist in the outer membrane, which act like pores for particular molecules
  5. There is a space between the layers of peptidoglycan and the secondary cell membrane called the periplasmic space
  6. If present, flagella have four supporting rings instead of two
  7. No teichoic acids or lipoteichoic acids are present
  8. Lipoproteins are attached to the polysaccharide backbone.
  9. Most do not form spores.
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33
Q

What is Lipid A?

A

Lipid A is found in Gram - bacterial cells

It is in the outtermembrane

It has very potent endotoxin activity

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34
Q

What is the medical importance of the bacterial cell wall?

A

It is used to identify the type of bacteria based on its gram staining reaction (Gram +, Gram -, or Gram non-reactive)

It is a target for host defense (Lysosyme)

It is a target for antibiotics (Penicillins)

35
Q

What is lysozyme?

A

This is an enzyme, in tears and syliva, that can degrade the bacterial cell wall.

36
Q

What is the gram staining process?

A
  1. Flood the slide with crystal violet solution for up to one minute. Wash off briefly with tap water (not over 5 seconds). Drain.
  2. Flood slide with Gram’s Iodine solution, and allow to act (as a mordant) for about one minute. Wash off with tap water. Drain.
  3. Remove excess water from slide and blot, so that alcohol used for decolorization is not diluted. Flood slide with 95% alcohol for 10 seconds and wash off with tap water. (Smears that are excessively thick may require longer decolorization. This is the most sensitive and variable step of the procedure, and requires experience to know just how much to decolorize). Drain the slide.
  4. Flood slide with safranin solution and allow to counterstain for 30 seconds. Wash off with tap water. Drain and blot dry with bibulous paper. Do not rub.
  5. All slides of bacteria must be examined under the oil immersion lens.
37
Q

Image of gram stain procedure.

A
38
Q

Second image of gram stain procedure.

A
39
Q

Why do Gram non-reactive bacterial cells not stain?

A

They do not have a cell wall and most are intracellular organisms; stains cannot reach them.

These organisms may weakly be Gram +

40
Q

What characteristics are limitations of the gram stain?

A

Having no cell wall

High lipid content in cell wall (This requires an acid fast stain)

Intracellular life cycle

To thin to be visulized

Lack of color under a microscope

41
Q

If gram staining cannot be performed, what other means can be used to stain?

A

Acid fast stains

Silver stains

Fluorescent antibody staining

Darkfield microscopy

42
Q

What color do Gram + bacteria stain?

A

Purple

43
Q

What color do Gram - organisms stain?

A

Pink to reddish

44
Q

What are the seven (7) major Gram + bacterial species that are associated with human disease?

A

Cocci: Staphlococcus, Enterococcus, & Streptococcus

Rods: Bacillus & Clostridium (Form spores) and Corynebacterium & Listeria (Non-spore formers)

NOTE: Listeria has an endotoxin-like molecule.

45
Q

What are the most clinically important Gram + cocci?

A

Staphylococcus (Catalase +)

* Staphyloccus aureus (Coagulase +)

* Other species (Primarily coagulase -)

Streptococcus (Catalase -)

* Beta-hemolytic streptococci

* Viridans (Nonhemolytic and alpha hemolytic) streptocci - Includes Streptococcus pneumoniae

Enterococcus (Catalase -)

* Enterococcus faecalis (Usually nonhemolytic)

* Enterococcus faecium (Usually alpha hemolytic)

46
Q

What is catalase?

A

Catalase is an enzyme that decomposes hydrogen peroxide to oxygen and water. It is present in almost all organisms.

It is important in that it protects bacteria from the oxidizing effects of hydrogen peroxide.

47
Q

What is coagulase?

A

Coagulase is an enzyme that enables the conversion of fribinogen to fibrin.

It allows bacteria to be protected from the immune system.

48
Q

What are the most important Gram + rods?

A

Spore forming rods

* Aerobes - Bacillus cerus, Bacillus anthracis

* Anerobes - Clostridium perfingens, septicum, difficile

Non-spore forming rods

* Uniform in shape - Listeria, Lactobacillus

* Irregular (Coryneform) in shape - Corynebactrium, Propionibacterium

Acid-fast rods

*Acid-fast - Mycobacterium

* Weak or partially acid-fast - Nocardia, Rhodococcus

49
Q

What are some of the clinically important Gram - rods?

A

Enterics

Anaerobes

Haemophilus

Bordetella

Legionella

Yersinia

Francisella

Pasteurella

Helicobacter

Vibrio

Campylobacter

Pseudomonas

Brucella

Gardnerella

50
Q

What are some of the clinically important Gram - cocci?

A

Neisseria gonorrhaea

Neisseria meningitidis

Haemophilus (Coccobacilli)

Acinetobacter (Coccobacilli)

Moraxella (Coccobacilli)

51
Q

What are some of the clinically important Gram - spirals?

A

Treponema

Borrelia

Leptospira

52
Q

What are some of the clinically important Gram - pleomorphic bacteria?

A

Chlamydia

Rickettsiae

53
Q

True or false; Gram - bacteria are some of the most commonly isolated bacteria.

A

True

54
Q

How does mycobacterium gram stain?

A

Mycobacterium does not normally stain using gram staining techniques.

It is acid-fast +, Gram non-reactive, and weakly gram +

55
Q

Why don’t spirochets stain well?

A

Spirochets are gram - but they are usually too small to see.

Must use darkfield or immunofluorescence to see.

56
Q

Why are Chlamydia and Rickettsiaes difficult to gram stain?

A

These are pleomorphic, intracellular organisms.

57
Q

What does pleomorphism mean in relationship to bacteria?

A

Pleomorphism means that the bacteria have the ability to alter their size and shape based on environmental conditions.

58
Q

Why is it difficult to perform gram staining on Mycoplasmas?

A

Mycoplasmas do not have a cell wall.

59
Q

What is the glycocalyx?

A

This is a ‘capsule’ that is made up of polysaccharides and is firmly attached to the cell wall in some bacteria.

Functions in protection and helps the microbe evade the host cell defense.

Also functions as a virulence factor and antigenic serotyping can be used to identify different strains of the microbe.

NOTE: Streptococcus pneumoniae

60
Q

What are bacterial flagella composed of and how does the flagella move?

A

Bacterial flagella are composed of a protein called flagellin.

The flagella is anchored to the cell membrane by a hook and basal body.

The number and arrangements of the flagella can be useful in identifying the bacteria.

The movement of the flagella is due to the movement of the basal body.

61
Q

Image of bacterial flaggela set=up.

A
62
Q

What is the basal body of the bacterial flagella made up of?

A

Rod

Integral proteins

Inner protein rings

63
Q

How is the flagella oriented within the bacterial Gram - cells?

A

The basal body resides in the cytoplasmic space of the cell membrane
.

The 1st outter ring is embeded within the peptidoglycan layer while the second outter ring is embeded in the outter membrane.

64
Q

How is the flagella oriented within bacterial Gram + cells?

A

The protein rings are embeded within the cytoplasmic membrane.

The rod spans the peptidoglycan layer.

There is no outter ring.

65
Q

Image of Gram - and Gram + bacterial flagella.

A
66
Q

What is the difference between Eucaryotic and Procaryotic flagella?

A

Eucaryotic flagella are made of microtubules.

Prokaryotic flagella are made of flagellin.

67
Q

What does monotrichious mean?

A

The bacterial cell has one polar flagella coming from one end of the cell.

68
Q

What does amphitrichous mean?

A

The bacteria has two flagella, one on each end of the cell.

69
Q

What does lophotrichous mean?

A

Lophotrichous means that the bacteria has multiple flagella in the same region of the cell. Usually at one end.

70
Q

What does peritichous mean?

A

Peritrichous means that the bacteria has many flagella all over the cell pointing in multiple directions.

71
Q

What is a pilius?

A

This is a hair-like appendage found on the surface of many bacterial cells.

Also known as fimbriae.

Used to attach to host cells.

Rarely found in Gram + cells

72
Q

What is a conjugation pilus or F pilus?

A

These are special pili that are used to transfer DNA from one cell to another.

73
Q

What is an endospore?

A

This is a dormant, tough covering that protects the bacteria from dessication and other harsh environmental conditions.

This is NOT a means of reproduction!!!

Under adverse conditions, sporulation occurs and when conditions improve, the spore germinates.

Seen in Bacillus and Clostridium species.

74
Q

What are bacterial inclusion bodies?

A

These store carbon, phosphate, and other molecules.

75
Q

What is contained within the periplasmic space?

A

Hydrolytic enzymes and binding proteins that are used for nutrient processing and uptake

76
Q

What is the nucleoid region?

A

This is the region of the bacterial cell where the genetic material is contained.

77
Q

What is a gas vacuole used for?

A

This is used for buoyancy and floating in an aquatic environment.

78
Q

What are the major serological molecules of enterobacteriaceae?

A

These are Gram - bacteria

Oxidase negative

O-antigen: LPS

K (VI) antigen: Capsule

H Antigen: Flagellum

79
Q

What is an endotoxin and where does it reside in bacteria?

A

Endotoxin is another name for LPS (Lipopolysacchairde)

They are found in the outter membranes of Gram - bacteria

80
Q

What is an exotoxin?

A

These are toxins that are secreted by bacteria.

81
Q

What is the significance of LPS and Lipid A?

A

LPS is only found in the outter membrane of Gram - cells

Lipid A is a component of LPS and is very toxic and stimulates rapid inflammation response by immune system. Can lead to Toxic Shock Syndrome.

LPS structure; Core, O-antigen, and Lipid A

82
Q

What does ‘normal flora’ mean?

A

This term refers to the organisms that normally inhabit an individual.

They typically do not cause disease but they can cause disease if they colonize sites of the body that should not be colonized.

83
Q

What factors influence microbial pathogenicity?

A
  1. Entry

2> Colonization

  1. Escape of host immune defenses
  2. Multiplication
  3. Damage of host tissues
84
Q

What are virulence factors and what are they related to?

A

These are chromosomal and extrachromosomal (plasmid) gene products that affect an organisms:

1) Invasivness
2) Adherence and colonization properties
3) Tissue damage / toxin production
4) Ability to elude host immune defenses
5) Antibiotic resistance

Microbiology (16 decks)

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