bacteria: structure, genetics and examples

Question 1

what are rod shaped bacteria called?

Answer 1

bacilli

Question 2

what are sphere shaped bacteria called?

Answer 2

cocci

Question 3

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

Answer 3

diplococcus

chains of cocci

clusters of cocci

chain of rods

curved rods

spiral rods

filamentous branching

Question 4

describe the structure of gram positive bacteria cell envelope

Answer 4

1 cell wall

its wall is thick and made of peptidoglycan

Question 5

describe the structure of gram negative bacteria cell envelope

Answer 5

2 membranes

Has a thin cell wall (made of Peptidoglycan)

plus an outer membrane that contains lipopolysaccharides

Question 6

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

Answer 6

endotoxin

Question 7

what colours do gram positive and negative stain?

Answer 7

Positive = PurPle

Negatove = piNk

Question 8

what colours do gram positive and negative stain?

Answer 8

Positive = PurPle

Negatove = piNk

Question 9

list other structures that a bacterial cell may contain

Answer 9

circular SNA

a capsule -sugar coating for extra protection

pili/flagella for motility

spores

Question 10

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

Answer 10

spores are made by bacteria

they are highly resistant to heat and chemicals

spores can last longer in water then bacteria

Question 11

what are endotoxins?

Answer 11

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

Question 12

what are exotoxins?

Answer 12

proteins secreted by bacteria which specific actions

Question 13

what is plasmid DNA?

Answer 13

additional bits of DNA that can swap between different bacterium

Question 14

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

Answer 14

base substitution

base deletion

base insertion

Question 15

how do bacterium transfer genes between them? 3 methods

Answer 15

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

Question 16

what are 2 factors that contribute to virulence?

Answer 16

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

Question 17

what bacteria are flora on the skin

Answer 17

Staphylococcus epidermidis

Question 18

what bacteria are flora on the oropharynx

Answer 18

Alpha-haemolytic streptococci

Question 19

what bacteria are flora on the large intestine

Answer 19

anaerobic bacteria:
Clostridium spp

Aerobic bacteria:
Enterococci

Question 20

what bacteria are flora on the vagina

Answer 20

Streptococcus spp

Bacteroides spp

Question 21

how do bacteria enter a host?

Answer 21

Respiratory tract
Gastrointestinal tract
Genitourinary tract
Skin break

Question 22

list some attributes of bacterial pathogens

that allow them to compete with host cells and flora

Answer 22

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

Question 23

what structures help bacteria to adhere to mucous surfaces ?

Answer 23

fimbriae + pili filamentous proteins (protrude out)

lipids in surface

other non-fimbrial proteins

Question 24

what are biofilms?

Answer 24

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

Question 25

why are biofilms advantageous?

Answer 25

Like this they are more resistant to antimicrobials

No longer in planktonic state (single)

Seen in dental plaques

Question 26

what cells are involved in the host response to bacterial infection?

Answer 26

IgA → block attachment to host cells

complement → cell lysis to prevent proliferation

antibodies→ prevent proliferation, neutralise toxins