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Bacteria Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define obligate anaerobes

A

Unable to grow in presence of oxygen

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2
Q

Define obligate aerobes

A

Need oxygen to survive, grow at atmospheric levels of oxygen.

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3
Q

Define facultative anaerobes

A

Use oxygen if present but can grow by fermentation if not.

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4
Q

Define microaerophiles

A

Require oxygen but below atmospheric levels of oxygen.

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5
Q

What is the bacterial cell wall composed of?

A

Peptidoglycan consisting of repeating units of N-acetyl glucosamine and N-acetyl muramic acid.

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6
Q

Difference between gram positive and gram negative?

A

Gram positive has a membrane and peptidoglycan outer wall, gram negative has an inner plasma membrane and outer lipid membrane with a thin layer of peptidoglycan in between.

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7
Q

Describe how to distinguish between gram positive and gram negative?

A

Make a film with gram positive and gram negative bacteria. Flood with crystal violet - all cells take up dye. Flood with Lugol’s iodine. All cells appear blue-black. Decolourise with acetone - gram positive retain dye complex, gram negative cells are decolourised. Counterstain with a red dye. Gram positive cells = blue black. Gram negative cells = red..

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8
Q

What is the function of fimbriae?

A

Fine, shorter hair-like filaments from cell surface, made of protein pilin, which are adhesins that mediate adhesion of bacteria to receptors on cell surface, teeth, etcs.

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9
Q

Define non-selective media

A

Permit growth of many microorganisms

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10
Q

Define differential media

A

Discriminate between microorganisms

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11
Q

Define selective media

A

Have inhibitors which only allow growth of specific species or type of microorganisms.

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12
Q

Give an example of differential media

A

Blood agar

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13
Q

Give an example of selective media

A

CCFA

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14
Q

What is used for biochemical tests?

A

API strip - allows identification of enteric bacteria.

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15
Q

What are the genetic methods of identification of bacteria?

A
  1. PCR methods.
  2. Ribosomal 16s RNA gene sequencing.
  3. Whole genome sequencing
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16
Q

Describe Ribosomal 16s RNA gene sequencing

A

For non-culturable organisms especially anaerobic bacteria with high complex growth requirements. Culture from infection shows negative result. Distinguishes between small differences in the 16s ribosomal RNA molecule. Pro - easy to standardise. Con - cost.

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17
Q

Define normal microbial flora

A

The population of microorganisms that inhabits the skin and mucuous membranes of healthy people.

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18
Q

Define resident flora

A

Relatively fixed types of microorganisms regularly found in a given area at a given age. If disturbed, it re-establishes itself.

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19
Q

Define transient flora

A

Non-pathogenic or potentially pathogenis microorganisms that inhabit the skin or mucuous membranes for hours or days.

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20
Q

What factors are reflected by resident flora?

A

Age, nutrition, sex, genetics, environment.

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21
Q

Mutualistic relationship means….

A

Benefits host and bacteria

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22
Q

Commensalistic relationship means …

A

Benefits bacteria, host is neither harmed nor benefits.

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23
Q

Parasitistic relationship means…

A

Benefits the bacteria but harms the host.

24
Q

Dysbiosis means…

A

Shift between healthy microflora to disease-associated ones.

25
Q

How does dysbiosis occur?

A

Abuse of antibiotics, radiation, surgery, use of immune suppressors, use of hormones, acquired immune deficiency.

26
Q

Which are the sterile sites in the body?

A

Blood, brain, muscle, cerebrospinal fluid.

27
Q

When can opportunistic pathogens cause disease?

A

In an immuno-compromised individual, when they change from their usual location.

28
Q

Define symbiosis

A

Equilibrium between dynamic and active factors. Dynamic = interactions, Active = diet, lifestyle, hormones, oral hygiene, host defenses.

29
Q

What factors can disrupt the symbiosis?

A

Inappropriate diet, inadequate plaque control, impaired saliva flow, altered host defences, lifestyle risk factors.

30
Q

Which bacteria cause caries?

A

Acidogenic bacteria. Mutans streptococci, lactobacilli.

31
Q

Which bacteria cause periodontal diseases?

A

Gram negative anaerobes - P. gingivalis, Tannerella forsythia, Aggregatibacter actinomycetemcomitans

32
Q

How does the tongue act as a microbial habitat?

A

Highly papillated surface, acts as a reservoir for obligate anaerobes. Facultative and obligate anaerobes. Streptococci, Actinomyces, Rothia, Neisseria.

33
Q

How do the teeth act as microbial habitats?

A

Non-shedding surface = large masses of microbes to accumulate = dental plaque biofilm. Smooth surfaces, pits and fissures. Diverse microflora. Streptococci, actinomyces, Fusobacterium.

34
Q

How do the cheeks lips and palate act as microbial habitats?

A

Desquamation limits biomass. Microflora has lower diversity. Facultative anaerobes present. Streptococci dominate.

35
Q

What is dental plaque?

A

Complex microbial community on the hard tissue surfaces of the mouth. Made of living, dead and dying bacteria and their products.

36
Q

What shape are gram positive organisms?

A

Rods, cocci or irregular shape.

37
Q

Name 3 gram positive organisms.

A

Streptococci (facultative anaerobic cocci, lactic acid). Lactobacillus (facultative anaerobe, lactic acid,). Actinomyces (facultative anaerobe)

38
Q

Strep mutans is associated with…

A

Caries, bacterial endocarditis. (Infective agent of caries)

39
Q

Strep salivarius colonises…

A

Mucosal surfaces, esp tongue.

40
Q

Where is strep mitis found?

A

Cheek, tongue, saliva, tooth.

41
Q

Where is strep salivarius found?

A

Tongue and saliva

42
Q

Where is strep mutans found?

A

Saliva and teeth

43
Q

Describe Actinomyces…

A
  1. Gram positive
  2. short pleomorphic rods with branching
  3. major proportion of plaque
  4. found in normal oral flora
  5. increase with gingivitis
  6. associated with root caries.
  7. facultative anaerobes
44
Q

What is the shape of gram negative organisms?

A

Cocci, rods, filamentous rods, spindle shaped or spiral shaped.

45
Q

Name 4 of the most important gram negative bacteria.

A

P gingivalis, P intermedia, F nucleatum, A. actinomycetemcomitans.
Also Treponema, Neisseria, Veillonella.

46
Q

Define virulence

A

Ability of an organism to infect the host and cause disease.

47
Q

Define virulence factors

A

Molecules that assist a bacterium to colonize the host, cause disease and evade host defences.

48
Q

Name the different virulence factors

A
  1. Adherence factors. - pili to adhere to cells.
  2. Invasion factors - surface components encoded on plasmids or chromosome.
  3. Capsules. - protect from opsonization and phagocytosis
  4. Endotoxins. - lipopolysaccharide endotoxins on Gram negative bacteria = fever, inflammation, shock.
  5. Exotoxins. - enzymes and toxins secreted by bacteria, eg cytotoxins and neurotoxins.
  6. Siderophores - iron-binding factors allowing competition for iron, which is bound to hemoglobin, transferrin and lactoferrin.
49
Q

How does F nucleatum produce virulence factors?

A

Coaggregates to form a bridge between early and late colonisers, helps increase pH of crevise for red complex bacteria.

50
Q

How does P gingivalis produce virulence factors?

A

Fimbriae, proteases, adheres to tissues, co-aggregates with other bacteria, invasive

51
Q

How does A actinomycetemcomitans produce virulence factors

A

Adhesins, bacteriocins, antibody-binding proteins, resistant to hydrogen peroxide, invasive

52
Q

How does T forsythia produce virulence?

A

Induces apoptosis, eliminating host cells.

53
Q

How does T denticola produce virulence?

A

Invasive, flagella for motility. (Gram negative spirochaete)

54
Q

How does P intermedia produce virulence?

A

Invasive, proteases, fimbriae (gram negative rod, black pigmented).

55
Q

Describe the flora of normal, healthy dentate mouth.

A

85%: Streptococci, Veilonella, Gram positive cocci and actinomyces, Gram negative anaerobic rods.
5-7% Neissaeria.
2% Lactobacilli.

Oral Biology (4 decks)

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