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Immunology Notes > Microbiology > Flashcards

Microbiology Flashcards

Basic Mibrobiology

1
Q

What bacterium is this?

A

Spirochetes

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2
Q

What bacterium is this?

A

Neisseria

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3
Q

Facultative anaerobes have . . .

A

the faculty to be aerobic, but they are not obligate to be so.

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4
Q

What bacterium is this?

A

Corynebacterium

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5
Q

Erythromycin

A

Antibiotic which targets the 50S subunit of the bacterial 70S ribosome.

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6
Q

Only known gram-negative coccus bacterium

A

Neisseria

A dipplococcus, meaning that two cocci remain adjacent to one another. Described as two coffee beans kissing.

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7
Q

What bacterium is this?

A

Streptococcus

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8
Q

This bacterium causes whooping cough.

A

Bordetella pertussis

B. pertussis uses its adhesins to bind to ciliated respiratory cells. These adhesins are vital to its pathogenicity.

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9
Q

Spirochetes

A

Gram-negative bacterium family containing Treponema pallidum, which causes syphilis.

Spirochetes have a gram-negative cell wall that stains with safranin, however are too small to be seen with a conventional light microscope. They must be visualized with a darkfield microscope.

In addition to the typical inner membrane-cell wall-outer membrane structure of other gram negative bacteria, spirochetes have another membrane over their gram-negative, LPS-contianing “outer” membrane. This special membrane has few exposed proteins, and as such protects spirochetes from immune recognition. Its flagella run sideways underneath this special membrane, making them periplasmic flagella. Their rotation propells the spirochete.

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10
Q

Major shapes of bacteria

A
  1. Cocci
  2. Bacilli
  3. Spiral-shaped
  4. Pleomorphic (lacking a distinct shape)
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11
Q

Why penicillin only works on gram-positive bacteria

A

The peptidoglycan layer surrounding gram-positive bacteria prevents the entry of large cargo into its branches, however small molecules like penicillin are small enough to diffuse through the holes.

The peptidoglycan layer in gram-negative bacteria are protected from even small molecules by their outer membrane, and so penicillin cannot reach its target in the peptidoglycan mesh.

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12
Q

Organisms that release pyrogenic exotoxins

A

Staphylococcus aureus

Streptococcus pyrogenes

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13
Q

Pili

A

Also called fimbriae.

Straight filaments arising from the bacterial cell wall. Can serve as adherence factors (in this case adhesins). In this case they are often vital for the adhesion and virulence of the bacteria.

May also be a sex pillus, which allows for the donation of plasmid DNA via horizontal gene transfer to another competent bacterium.

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14
Q

Two classically pathogenic gram-positive cocci

A

Streptococcus (can be identified by its tendency to form strips of cocci)

Staphylococcus (can be identified by its tendency to form clusters of cocci)

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15
Q

Exotoxins

A

Proteins released by gram-positive or -negative bacteria that may cause disease manifestations.

Produced by all major gram-positive bacteria except Listeria monocytogenes (which produces endotoxin).

Exotoxin-induced diseases include anthrax, botulism, tetanus, and cholera.

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16
Q

Gram-Positive organisms

A

Organisms that stain blue with the crystal violet dye.

Have a peptidoglycan cell wall over a cytoplasmic membrane.

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17
Q

Mycobacteria

A

An exception to the gram stain rule.

Weakly gram-positive, but stain better with a special stain called the acid-fast stain.

This group incudes organisms that cause tuberculosis and leprosy.

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18
Q

What bacterium is this?

A

Clostridium

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19
Q

This bacterium causes gonnorhea.

A

Neisseria gonorrhea

The adhesins of N. gonorrhea allow it to bind to cervical cells and buccal cells. These adhesins are vital for the pathogenicity of N. gonorrhea.

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20
Q

Tetracycline

A

Antibiotic which targets the 30S subunit of the bacterial 70S ribosome.

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21
Q

Capsules

A

Protective walls that surround the cell membrane of gram-positive and -negative bacteria.

Usually composed of sugar residues.

Help prevent detection of the bacterium by hiding its protein antigens.

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22
Q

The Gram Stain Protocol

A
  1. Pour on crytal violet and wait 60 seconds.
  2. Wash off with water and flood with iodine solution. Wait 60 seconds.
  3. Wash off with water and “decolorize” with 95% alcohol.
  4. Finally, counter-stain with safranin. Wait 30 seconds and wash off with water.
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23
Q

Gram-negative endotoxin

A

Another name for lipid A, the inner lipid region of LPS which connects it to the gram-negative outer membrane.

Toxic to humans - may vcause fever, diarrhea, and possibly endotoxic shock/septic shock.

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24
Q

Common facultative intracellular organisms

A
  1. Listeria monocytogenes
  2. Salmonella typhi
  3. Yersinia
  4. Francisella tularensis
  5. Brucella
  6. Legionella
  7. Mycobacterium
25
Q

What bacterium is this?

A

Bordetella pertussis

26
Q

The most common vaccine against streptococcus pneumoniae carries antigens from ______ in order to induce tolerance.

A

The most common vaccine against Streptococcus pneumoniae carries antigens from 23 of the most common Streptococucs capsule proteins in order to induce tolerance.

27
Q

Virulence

A

Degree of pathogenicity

28
Q

Bacterial DNA

A

Consists of a single circle of double-stranded DNA and smaller plasmids which may be exchanged with other competent cells.

29
Q

Common causes of infectious diarrhea

A

Enterotoxins derived from:

Vibrio cholera

Escherichia coli

Campylobacter jejuni

Shigella dysenteriae

30
Q

Mycoplasma

A

Bacterium with no cell wall. They have only a simple cell membrane, and are therefore neither gram-positive or gram-negative.

31
Q

Endospores are only formed by. . .

A

2 genera of bacteria:

The aerobic Bacillus

and

the anaerobic Clostridium.

32
Q

Gram-Negative organisms

A

Organisms that stain red with the safranin dye.

Have an outer membrane, over a peptidoglycan cell wall, over a small periplasmic space, over an inner cytoplasmic membrane.

Murein lipoprotein extends from the cell wall into the outer membrane.

The outermost membrane of gram-negative bacteria contains LPS.

33
Q

Autotrophs

A

Utilize inorganic chemical sources such as carbon dioxide, ammonium, sulfate, etc.

34
Q

Unlike the membrane of animal cells, the bacterial membrane contains no . . .

A

cholesterol or derivative sterols.

35
Q

Endospores

A

Metabolically dormant forms of bacteria that are resistant to harsh conditions. Have a multi-layered coat consisting of:

  1. Cell Membrane
  2. Thick peptidoglycan mesh
  3. Another cell membrane
  4. A wall of keratin-like protein
  5. An outer layer called the exosporium
36
Q

Enterotoxins

A

Exotoxins that act on the GI tract to cause diarrhea.

37
Q

All of the medically important bacteria are . . .

A

chemoheterotrophic.

38
Q

Structure of a Flagellum

A

Exist in both gram-positive and -negative bacteria.

Affixed to the bacteria by a basal body​, which spans the entire cell wall, to the inner membrane in both gram-positive and -negative bacteria.

39
Q

Quellung reaction

A

Bacteria are mixed with antibodies that bind their capsule. When the antibodies bind, the capsule swells with water. This process may be visualized under a microscope.

40
Q

What bacterium is this?

A

Bacillus

41
Q

Common causes of food poisoning

A

Enterotoxin released by:

Bacillus cereus

Staphylococcus aureus

42
Q

Structure of LPS

A

The outer region of LPS is a carbohydrate chain of 1-50 oligosaccharide units. These differ slightly from one organism to another and are antigenic determinants, hence its nick-name as the O-antigen.

The middle region of LPS is a water-soluble core polysaccharide.

The inner region of LPS (which interfaces with the outer gram-negative bacterial membrane) is named lipid A. It is a disaccharide with mutliple fatty acid tails reaching into the membrane. It is toxic to humans, and thus is also known as the gram-negative endotoxin.

43
Q

What bacterium is this?

A

Listeria

44
Q

Obligate intracellular organisms

A

Incapable of the metabolic pathways for ATP synthesis and thus must steal ATP from their host.

Ex. Chlamydia and Rickettsia

45
Q

Transpeptidase

A

Catalyzes the formation of the cross-links in the peptidoglycan layer of gram-positive and -negative bacteria.

This enzyme is the target of penicillin and other beta-lactam antibiotics, and so is also known as penicillin binding protein.

46
Q

This stain is used to visualize the capsules of bacteria

A

India ink stain

The capsule appears as a halo around the cell.

Used primarily to identify Cryptococcus.

47
Q

What bacterium is this?

A

Bacillus anthracis

48
Q

Apart from ___ and ___, all gram-negative bacteria are ___ or ___.

A

Apart from Neisseria and Spirochetes, all gram-negative bacteria are bacilli or pleomorphic.

49
Q

Only known group of spiral-shaped gram-negative bacteria

A

Spirochetes

This bacterium is responsible for syphilis

50
Q

What bacterium is this?

A

Staphylococcus

51
Q

What bacterium is this?

A

Cryptococcus

Stained with the india ink stain to visualize capsules.

52
Q

Examples of neurotoxin

A

Tetanus toxin

Botulinum toxin

53
Q

6 Classical gram-positive bacteria that cause disease in humans

A

Note: These are the only common gram-positive bacteria that infect humans, almost all other infections are gram-negative.

  1. Streptococcus
  2. Staphylococcus
  3. Bacillus
  4. Claustridium
  5. Corynebacterium
  6. Lysteria
54
Q

Microaerophilic bateria

A

Also called aerotolerant anaerobes

Use fermentation and have no electron transport system/ They can tolerate low amounts of oxygen due to the presence of superoxide dismutase, but have no catalase.

55
Q

O-antigen

A

Another name for the outer polysaccharide region of LPS.

56
Q

This bacterium is unique in that its capsule is made up of amino acid residues.

A

Bacillus anthracis

57
Q

Teichoic acid

A

An important polysaccharide present in the gram-positive bacterium cell wall.

Strongly antigenic and is used as a serological determinant for many gram-positive species.

58
Q

Four classically pathogenic gram-positive bacilli

A

Spore forming:

Bacillus

Clostridium

Non-spore forming:

Corynebacterium

Listeria

Immunology Notes (24 decks)

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