bacteria: structure, genetics and examples Flashcards

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1
Q

what are rod shaped bacteria called?

A

bacilli

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2
Q

what are sphere shaped bacteria called?

A

cocci

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3
Q

other than as cocci or bacilli, in what other forms can bacteria be seen in?

A

diplococcus

chains of cocci

clusters of cocci

chain of rods

curved rods

spiral rods

filamentous branching

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4
Q

describe the structure of gram positive bacteria cell envelope

A

1 cell wall

its wall is thick and made of peptidoglycan

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5
Q

describe the structure of gram negative bacteria cell envelope

A

2 membranes

Has a thin cell wall (made of Peptidoglycan)

plus an outer membrane that contains lipopolysaccharides

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6
Q

the gram negative outer membrane made of lipopolysaccharides is also known as ?

A

endotoxin

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7
Q

what colours do gram positive and negative stain?

A

Positive = PurPle

Negatove = piNk

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8
Q

what colours do gram positive and negative stain?

A

Positive = PurPle

Negatove = piNk

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9
Q

list other structures that a bacterial cell may contain

A

circular SNA

a capsule -sugar coating for extra protection

pili/flagella for motility

spores

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10
Q

what are spores and why are they useful for the bacteria?

A

spores are made by bacteria

they are highly resistant to heat and chemicals

spores can last longer in water then bacteria

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11
Q

what are endotoxins?

A

endotoxin is the component of the outer membrane of gram negative bacteria

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12
Q

what are exotoxins?

A

proteins secreted by bacteria which specific actions

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13
Q

what is plasmid DNA?

A

additional bits of DNA that can swap between different bacterium

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14
Q

what are the 3 mutations that can occur in bacteria DNA?

A

base substitution

base deletion

base insertion

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15
Q

how do bacterium transfer genes between them? 3 methods

A
  1. transformation (take DNA from environment)
  2. transduction (bacteria is infected by a virus which passes its DNA on)
  3. conjugation (via plasmid transfer )
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16
Q

what are 2 factors that contribute to virulence?

A
  1. colonisation factors - : adhesins, invasins, nutrient acquisition, defence against the host
  2. toxins
17
Q

what bacteria are flora on the skin

A

Staphylococcus epidermidis

18
Q

what bacteria are flora on the oropharynx

A

Alpha-haemolytic streptococci

19
Q

what bacteria are flora on the large intestine

A

anaerobic bacteria:
Clostridium spp

Aerobic bacteria:
Enterococci

20
Q

what bacteria are flora on the vagina

A

Streptococcus spp

Bacteroides spp

21
Q

how do bacteria enter a host?

A

Respiratory tract
Gastrointestinal tract
Genitourinary tract
Skin break

22
Q

list some attributes of bacterial pathogens

that allow them to compete with host cells and flora

A

Sequestering nutrients

Using novel metabolic pathways

Out competing other microorganisms

Use a ‘two component sensor kinase’ to sense changes in competing bacteria, nutrient availability etc.

alter their own genes eg. to produce more toxins

23
Q

what structures help bacteria to adhere to mucous surfaces ?

A

fimbriae + pili filamentous proteins (protrude out)

lipids in surface

other non-fimbrial proteins

24
Q

what are biofilms?

A

Bacteria secrete an extracellular polymeric substance of protein, polysaccharides and DNA to help them stick together on a surface

25
why are biofilms advantageous?
Like this they are more resistant to antimicrobials No longer in planktonic state (single) Seen in dental plaques
26
what cells are involved in the host response to bacterial infection?
IgA → block attachment to host cells complement → cell lysis to prevent proliferation antibodies→ prevent proliferation, neutralise toxins