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Foodborne Pathogens > PowerPoint 2 : Review of bacteria > Flashcards

PowerPoint 2 : Review of bacteria Flashcards

1
Q

What type of bacteria has lipoteichoic acid?

A

Gram Positive

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2
Q

Which bacteria has an outer membrane?

A

Gram Negative

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3
Q

What is the role of adding iodide to the Gram stain?

A

Binds crystal violet and traps it in the peptidoglycan

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4
Q

What is the purpose of alcohol in the Gram Stain?

A

Cells are de-stained

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5
Q

Which cells retain the purple die?

A

Gram positive

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6
Q

Why do we add safranin or Carbol Fushin?

A

Stains the gram negative cells pink

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7
Q

Pili are found on most gram positive cells (T/F)?

A

False

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8
Q

Teichoic acid is found on gram positive cells (T/F)?

A

True

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9
Q

Lipopolysaccharides are found on gram positive cells (T/F)?

A

False

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10
Q

What are lipopolysaccharides made of?

A
  • lipid A
  • core
  • repeating oligosaccharide (O antigen)
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11
Q

What is the polysaccharide layer that lies outside the cell envelope of bacteria?

A

Capsule

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12
Q

Which organelle mediates attachment to other cells or surfaces?

A

Fimbrae and Pili

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13
Q

What is an adhesin pili?

A

Pili with an adhesin protein that allows the cell to stick to human cells. Some mediate genetic exchange.

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14
Q

Where are sex pili found?

A

On Enteric Bacteria

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15
Q

On which bacteria is the sex pili coded for by a conjugative transmissible plasmid (F plasmid), which resides in the donor cell?

A

E.coli

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16
Q

What is the stiff helical organelle of locomotion that protrudes from the cell surface and allows swimming?

A

Flagellum

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17
Q

What is the capsule K antigen?

A

Capsular polysaccharide associated with cell surface non-covalently and protects bacteria from the host immune system.

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18
Q

What is the lipopolysaccharide O antigen?

A

Also known as lipoglycan and endotoxin.

  • A hydrophobic lipid section, lipid A, which is responsible for the toxic properties of the molecule
  • A hydrophilic core polysaccharide chain, a
  • A repeating hydrophilic O-antigenic oligosaccharide side chain that is specific to the bacterial serotype
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19
Q

What is the protein antigen found on the surface of some gram-positive, and some gram-negative bacteria, rarely used in classification?

A

Fimbriae F antigen

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20
Q

What is the antigen that based on the reaction with the flagellin protein arranges itself in a hollow cylinder to form the filament in a bacterial flaegellum?

A

Flagella H antigen

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21
Q

What antigens is e.coli 157:H7 type based on?

A

O and H antigens

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22
Q

What antigen is Listeria Monocytogenes based on despite the fact that the semantics are 1/2a, 1/2b, 4b, etc.?

A

Based on O and H antigens

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23
Q

Although they are typed based on O and H antigens, what bacteria is given a name based on where it was discovered?

A

Salmonella

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24
Q

For salmonella, instead of calling them serotypes what are they called?

A

serovars

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25
Q

What pathogen is based of the O and K antigens (and O4:K12 is the most common cause of illness in Canada?)

A

Vibrio Parahaemolyticus

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26
Q

What bacteria is based on toxins A,E, F?

A

Clostridium Botulinum

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27
Q

In what type of media can injured cells grow?

A

non-selective media

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28
Q

What type of cells can appear dead due to the use of selective media in termal studies, so then the thermal resistance will be underestimated and the the true kill values will be low?

A

Injured cells

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29
Q

What type of cells make escape routine detection post-processing leading to faster spoilage or a safety problem?

A

Injured cells

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30
Q

What are salt, organic acids, and suboptimal temperatures examples of?

A

Selective agents

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31
Q

What requires de novo RNA and protein synthesis and is during the lag phase?

A

Recovery

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32
Q

How can peroxide detox agent help in recovery?

A

Can help overcome damage caused by oxygen toxicity

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33
Q

What is the state of the cell called when it cannot be cultured on any media even though their viability can be demostrated by non-culturable methods.

A

viable but not coluturable (VBNC)

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34
Q

Salmonella, Campylobacter, Eschrichia, Shigella, Yersinia pestis, Vibrio, can exist in what type of state?

A

VBNC

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35
Q

What is a survival strategy for non-sporulating species?

A

VBNC

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36
Q

True or false: the VBNC state is morphologically the same form that of a normal vegetative cell.

A

false: its different

37
Q

Red fluorescent nucleic acid stains are incubated with cells, if they permeate what does it indicate?

A

The cells is dead

38
Q

What color will bacteria with intact membrane stain?

A

Intact membrane: green

Damaged membrane: red

39
Q

What is substrate responsive metabolism?

A
  • can be used to detect viability
  • cells can be incubated with a nutrient (yeast extract) and an antibiotic that inhibits cell division (nalidixic acid, cirpofloxacin)
  • live cells elongate but do not divide
40
Q

What method can show listeria monocytogenes is viable?

A

substrate responsive metabolism

41
Q

What often induces VBNC state?

A
  • nutrient limitation

- also salt concentration, exposure to chemicals, and temperature shifts

42
Q

T/F: VBNC can be resuscitated by temperature shifts and a gradual return of nutrients.

A

True

43
Q

Vibrio Vulnificus is commonly found in what type of food?

A

Shellfish such as oysters

44
Q

How many bacteria in the biosphere may be unculturable?

A

As many as 99%

45
Q

What regulates genes that would be superfluous to isolated cells but that are useful to large populations?

A

quorum sensing

46
Q

Quorum sensing is based on diffusion of a signal molecule produced in large amounts (T/F)?

A

true

47
Q

What type of response does quorum sensing elicit?

A

phenotypic response

48
Q

What is signal transduction?

A

two components regulatory system where one protein spans the membrane, picks up a signal and then reacts based on a response regulator protein.

49
Q

What is quorum sensing systems built on?

A

auto-inducers which diffuse through the cellular membrane to initiate a specific response when a certain population density has been reached

50
Q

What acts a signaling molecule in gram negative bacteria for quorum sensing?

A

N-acyl homoserine lactone (AHL) molecules

51
Q

How is probiotic bacteria thought to prevent infection by pathogenic bacteria?

A

Lactobacillus acidophilus prevents e.coli infection by produce small biologically active molecules that interfere with the quorum sensing system of e.coli.
-this limits the pathogen’s ability to adhere to tissues and cause lesions.

52
Q

What are the two components in signal transduction?

A
  • Histidine Kinase Receptor

- Response Regulator

53
Q

What signal system does L.monocytogenes have?

A

Signal Transduction

54
Q

What signal system does s.aureus have?

A

Signal Transduction

55
Q

What signal system does lactic acid bacteria have?

A

Signal Transduction

56
Q

What signal system does S.enterica serovar typhimurium have?

A

Quorum sensing

57
Q

What signal system does enteropathogenic e.coli have?

A

Quorum sensing

58
Q

What signal system does v.cholerae have?

A

Quorum sensing

59
Q

What is a biofilm?

A

Aggregation of cells, often multiple species, into heterogeneous complex structures that are attached to a solid surface

60
Q

What is the purpose of defined boundaries in biofilms?

A

Allow fluid channels to run through the biomatrix. Critical for bringing in nutrients and carrying away waste.
-resistant to heat, chemicals, sanitizers

61
Q

What are endospores?

A

Differentiated cells that are very resistant to heat and cannot be easily destroyed even by chemicals

62
Q

What are the two pathogens infamous for causing illness after consumption of food with germinated spores?

A
  • clostridium botulinum

- bacillus cereus

63
Q

T/F: Bacterial chromosomes are plastic

A

True

64
Q

What is the geometry of Borelia burgdorferi and Giardia lamblia’s chrosome?

A

Linear

65
Q

How many chromosomes does Giardia have?

A

Four

66
Q

What is the term that defines the genes that are shared by all members of a certain group?

A

Core Genome

67
Q

What is the term that includes the genes that are present in any member of a certain group?

A

Pangenome

68
Q

What is the term that describes the genes that are present in a subset of members of a certain group?

A

Accessory Genome

69
Q

What are the mobile genetic elements that contribute to diversity in bacteria?

A
  • bacteriophage
  • plasmids
  • pathogenicity islands
  • transposons
70
Q

What is a prophage?

A

A bacteriophage or phage genome inserted and integrated into the circular bacterial DNA chromosome or existing as an extrachromosomal plasmid.

71
Q

What do prophages carry?

A

Genes for virulence factors or toxins required for pathogenesis by the pathogens they lysogenize

72
Q

What is the process by which a prophage converts a non-pathogenic bacteria into a pathogen?

A

Lysogenic Conversion

73
Q

What bacteria is not pathogenic until infected with a phage CTX that carries the gene for the cholera toxin?

A

Vibrio cholerae

74
Q

What are the vibrio cholerae serotypes that are pathogenic?

A

O1 and O139

75
Q

What are circular molecules (some exceptions) of double-stranded DNA called which are self-replicating?

A

Plasmids

76
Q

Do plasmids carry essential genes?

A

No. They carry genes which encode for products which can benefit the bacteria under certain circumstances (i.e AMR genes).

77
Q

What are pathogenicity islands and what do they allow?

A
  • DNA elements integrated in the chromosome of some bacteria which contain genes that confer special properties
  • Allow the bacteria carrying them to occupy special ecological niches (i.e AMR genes).
78
Q

Are pathogenicity islands able to move from one bacteria to another, even in unrelated strains?

A

Yes

79
Q

What gene is essential to pathogenicity islands and allows them to integrate the host DNA?

A

Integrase Gene

80
Q

What is the role of the repeated sequence at the end of pathogenicity island’s sequences?

A

Involved in integration

81
Q

What are DNA elements that can hop from one place in chromosomal DNA to another?

A

Transposon

82
Q

What does transposon DNA have that gives it the ability to hop each time it moves?

A

Transposase Gene

83
Q

What are the few types of bacterial transposons?

A
  • Insertion Sequence (IS) Elements

- Composite Transposons

84
Q

What are Insertion Sequences (IS) Elements?

A
  • smallest transposons
  • really only encode the transposon
  • can interrupt gene function by inserting in the middle of a gene
  • have Inverted Repeat (IR) at either end
85
Q

What are composite transposons?

A

When two IS elements bracket other genes and carry those other genes with them when they move.
(i.e: Transposase Gene + 3 other genes + Transposase Gene)

86
Q

What is the transmission of DNA from mother to daughter cells called?

A

Vertical Gene Transfer

87
Q

What is intoxication?

A

Ingestion of bacterial or mould toxin, which must be present in its active form.

88
Q

What is infection?

A

Illness that occurs after the consumption of viable bacterial cells or viruses.

89
Q

What is a toxico-infection?

A

When illness occurs from the ingestion of a large number of viable cells of some pathogenic bacteria.
-the bacteria cells either sporulate, colonize, or die, and release the toxins.

Foodborne Pathogens (11 decks)

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