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BM211: Introduction to Microbiology > Block B Lecture 2 - Gram-Negative Bacteria > Flashcards

Block B Lecture 2 - Gram-Negative Bacteria Flashcards

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1
Q

What is the defining feature of a gram-negative bacteria?

A

Its outer membrane
(Slide 3)

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2
Q

What is gram staining based on?

A

The fact that the peptidoglycan layer is much thinner in gram negative bacteria when compared to gram positive bacteria
(Slide 3)

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3
Q

What colour do gram-positive and gram-negative bacteria appear in gram-staining?

A

gram-positive bacteria appear either purple or blue whereas Gram-negative bacteria appear appear either pink or red
(Slide 3)

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4
Q

What are fimbriae and flagella?

A

Fimbriae are short hair-like appendages which protrude from the surface of bacterial cells and flagella are long whip-like appendages which protrude from the surface of bacterial cells
(Slide 4)

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5
Q

What are fimbriae and flagella used for?

A

Fimbriae are used for adhesion whereas flagella are used for motility
(Slide 4)

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6
Q

What do conjugative pili (fimbriae) facilitate?

A

The transfer of DNA between bacteria during bacterial conjugation
(Slide 4)

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7
Q

What is bacterial conjugation?

A

A mechanism of horizontal tranfer, where DNA is exchanged between bacteria, usually in the form of plasmids
(Slide 4)

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8
Q

What is a key virulence factor for many gram-negative bacteria?

A

The type III secretion system
(Slide 4)

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9
Q

What is a bacterial envelope?

A

The complex structure surrounding a bacterial cell which provides structural integrity, protection and a barrier between cells interior and the external environment
(Slide 5)

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10
Q

Describe the structure of a gram-negative bacteria’s envelope.

A

It has a cell wall which itself is made up of an outer membrane and the periplasm and has a thin peptidoglycan layer contained in the periplasm (an intermembrane space present in the envelop of gram-negative bacteria) the envelope also may or may not contain a capsule or S-layer
(Slide 5)

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11
Q

What are 2 functions of the outer membrane of gram-negative bacteria?

A

It acts as the first line of defence against antibiotic therapy, disinfectants and host immune response
Acts as a selectively permeable barrier
(Slide 6)

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12
Q

State 5 ways that the outer membrane of gram-negative bacteria can act as a selectively permeable barrier.

A

Nutrients can enter through protein channels
Large antibiotics are excluded
Small antibiotics can diffuse through protein channels
Hydrophobic antibiotics can diffuses poorly across the outer membrane
It protects the cell from bile salts such as cholic acid and deoxycholic acids and other detergents such as SDS
(Slide 6)

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13
Q

What is the biggest problem we face in treating bacteria?

A

Anti-microbial resistance
(Slide 7)

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14
Q

What kind of bacteria causes the majority of anti-microbial resistance (AMR) deaths worldwide?

A

Gram-negative bacteria
(Slide 8)

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15
Q

What 3 bacteria cause over 50% of global bloodstream infections (BSIs)?

A

E. coli, S. aureus and K. pneumoniae
(Slide 8)

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16
Q

Why do we mainly study the Bacteroidetes and Proteobacteria (Pseudomonas) phyla of gram-negative bacteria?

A

Bacteroidetes as they are a major component of human gut microbiota
Proteobacteria as they can cause disease
(Slide 9)

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17
Q

Where can we find proteobacteria?

A

In all major ecosystems, though they are not a major component of normal gut microbiota
(Slide 10)

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18
Q

Why is having elevated levels of proteobacteria in the gut not good?

A

As it indicates a dysbiotic microbiome which can lead to gastric bypass, metabolic disorders, inflammation and cancer
(Slide 10)

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19
Q

What is a dysbiotic microbiome?

A

A dysbiotic microbiome refers to an imbalance or disruption in the composition and function of the microbial communities residing in a particular environment
(Slide 10)

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20
Q

Proteobacteria are the most metabolically diverse of all bacteria, state 3 different methods of metabolism they can have.

A

Chemolithotrophy
Chemoorganotrophy
Phototrophy
(Slide 11)

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21
Q

What are the 5 classes that Proteobacteria can be divided into?

A

Alpha
Beta
Delta
Gamma
Epsilon
all have “Proteobacteria” following this
(Slide 11)

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22
Q

What are 3 features that many Alphaproteobacteria have?

A

Many are obligate or facultative aerobes and many are oligotrophic (able to grow in low nutrient environments)
(Slide 12)

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23
Q

What are the 6 major orders of Alphaproteobacteria?

A

Rhizobiales
Rickettsiales
Rhodobacterales
Rhodospirillales
Caulobacterales
Sphinomonadales
(Slide 12)

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24
Q

What are Rickettsia spp.?

A

A family of obligate intracellular bacteria contained within the Rickettsiales order which are mostly associated to arthropods
(Slide 13)

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25
Q

Where must Rickettsia spp. bacteria get certain metabolites from?

A

They must get them from their host and they are unable to synthesise them
(Slide 13)

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26
Q

How can some Rickettsia spp. bacteria infect mammalian hosts?

A

Mostly through arthropods (tick, fleas etc) through their bites or faeces
(Slide 13)

27
Q

What is Caulobacter crescentus (in the Caulobacterales order within the Alphaproteobacteria class) a model organism for?

A

Asymmetric cell division and cellular differentiation
(Slide 14)

28
Q

What are the 2 cells types that Caulobacter crescentus can produce and what are their functions?

A

Stalked cells which forms biofilms to exploit nutrient sources and swarmer cells which are motile to allow them to seek out new environments
(Slide 14)

29
Q

What are the 6 major orders contained in the Betaproteobacteria class?

A

Burkholderiales
Hydrogenphilales
Methylophilales
Niesseriales
Nitrosomonadales
Rhodocyclales
(Slide 16)

30
Q

What 2 diseases does Neisseria meningitidis cause?

A

Meningitis and meningococcal septicaemia (a blood stream infection that damages the walls of the blood vessels)
(Slide 17)

31
Q

In what age groups is Neisseria meningitidis more common in?

A

Infants, teens and young adults (it also only infects humans)
(Slide 17)

32
Q

What is Neisseria gonorrhoeae?

A

It is responsible for the development of the STI gonorrhoea
(Slide 18)

33
Q

Approximately what percentage of Neisseria gonorrhoeae infections are asymptomatic?

A

10%
(Slide 18)

34
Q

Why is Neisseria gonorrhoeae a major public health concern?

A

Due to the spread of highly resistant strains
(Slide 18)

35
Q

What is Bordetella pertussis the causative agent for?

A

Pertussis, AKA whooping cough
(Slide 19)

36
Q

What is Pertussis (whooping cough)

A

A seriously and highly infectious respiratory disease affecting mostly children
(Slide 19)

37
Q

How can pertussis be prevented and treated?

A

Can be prevented by vaccination and treated with antibiotics
(Slide 19)

38
Q

What are the 2 main orders contained within the Gammaproteobacteria class?

A

Enterobacteriales and Pseudomonadales
(Slides 21 - 26)

39
Q

What does enteric bacteria (referring to enterobacteriales) mean?

A

That they primarily inhabit the gastrointestinal tract
(Slide 21)

40
Q

What are 3 features of enterobacteriales?

A

They primarily inhabit the gastrointestinal tract
They are facultative aerobes
They can be motile or nonmotile
They are nonsporulating
They are rod shaped
Have relatively simple nutritional requirements
Ferment sugars to a variety of end productions
(Slide 21)

41
Q

How can enteric (enterobacterial) bacteria be separated into 2 broad groups and what groups are they?

A

Separated by the type and proportion of fermentation productions generated by anaerobic fermentation of glucose with the 2 groups being:
Mixed-acid fermenters
2,3-butanediol fermenters
(Slide 22)

42
Q

What are 3 examples of enterobacteriales genera whose bacteria are mixed acid fermenters?

A

Escherichia
Salmonella
Shigella
(Slide 23)

43
Q

What genus are salmonella and shigella closely related to?

A

Escherichia
(Slide 23)

44
Q

What does Escherichia presence in water indicate?

A

Recent faecal contamination
(Slide 23)

45
Q

What is salmonella characterised immunologically by?

A

Surface antigens
(Slide 23)

46
Q

What 2 surface antigens can salmonella have and where are these based?

A

An O antigen based on the outer region of the lipopolysaccharide
A H antigen based on flagellar proteins
(Slide 23)

47
Q

What are 2 genera in the enterobacteriales class which are butanediol fermenters?

A

Enterobacter
Klebsiella
(Slide 25)

48
Q

Where are bacteria in the Enterobacter genus found?

A

In water, sewage and the intestinal tract of warm-blooded animals
(Slide 25)

49
Q

What disease can bacteria in the Enterobacter genus cause?

A

They can cause urinary tract infections (UTIs)
(Slide 25)

50
Q

Where are klebsiella bacteria found?

A

In soil and water
(Slide 25)

51
Q

What do most strains of klebsiella fix?

A

Nitrogen
(Slide 25)

52
Q

What 3 infections / diseases can klebsiella pneumoniae cause?

A

Pneumonia, UTIs and bacteremia (the presence of bacteria in the blood)
(Slide 25)

53
Q

Why is Pseudomonas aeruginosa a major health concern?

A

As it is a major cause of serious hospital acquired infections associated with high levels of AMR and it can cause infections at multiple body sites
(Slide 26)

54
Q

What is the main order in the Epsilonproteobacteria class?

A

Campylobacterales
(Slide 28)

55
Q

Where can campylobacter jejuni most common be acquired?

A

It’s foodborne and is most commonly acquired from undercooked poultry (bird), pork or raw shellfish
(Slide 28)

56
Q

What are 3 symptoms of campylobacter jejuni?

A

Diarrhea (often bloody), fever and stomach cramps
(Slide 28)

57
Q

What are the 2 main orders in the Deltaproteobacteria class?

A

Bdellovibrionales
Myxococcales
(Slides 30 and 31)

58
Q

What are the 5 main genera in the Deltaproteobacteria class?

A

Bdellovibrio
Myxococcus
Desulfovibrio
Geobacter
Syntrophobacter
(Slide 29)

59
Q

What are the key features of Deltaproteobacteria?

A

They reduce sulphate, sulphur and are Dissimilative iron reducers.
They are bacterial predators

(Slide 29)

60
Q

What is the key feature of Bdellovibrio bacteria?

A

They are microbial predators
(Slide 30)

61
Q

What are microbial predators?

A

Any microorganism which preys on other microorganisms as a source of nutrition
(Slide 30)

62
Q

What is the life cycle of myxococcus xanthus?

A

It begins in either the vegetative or swarm stage where individual cells move and feed co-operatively in a process called swarming. When nutrients become depleted they start to form multicellular structures called “mounds” which then undergo further differentiation and morphogenesis to form fruiting bodies with vegetative cells forming the stalk and a subset of cells undergoing sporulation to become spores, before then being positioned at the tips of the stalk.
Once sporulation is complete, the mature fruiting bodies release spores into the environment which can then remain dormant for extended periods of time until they encounter suitable conditions for germination
(Slide 31)

63
Q

What is germination?

A

When a spore begins to grow vegetative cells
(Slide 31)

BM211: Introduction to Microbiology (21 decks)

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