Gram Positive and Gram Negative Bacteria I and II

Question 1

describe the equation for CFU/mL

Answer 1

Question 2

describe the 4 stages of bacterial growth

Answer 2

Question 3

describe how turbidity can be used to assess bacterial growth

Answer 3

Question 4

smaller size = better ___ to ___ ratio

Answer 4

smaller size = better surface area to volume ratio

substances enter and diffuse quickly

Question 5

describe the association between arrangement and cell shape

Answer 5

Question 6

describe cellular features unique to bacteria

Answer 6

• flagella for motility
• peptidoglycan cell wall
• capsule
• lipopolysaccharide (G-ve)
• type of communication

Question 7

name features that are common to both G+ve and G-ve bacteria

Answer 7

• cytoplasmic membrane that lacks cholesterol
• cell wall made of peptidoglycan
  
  • structurally slightly different in G+ve vs G-ve
    
    • basis of the Gram stain for differentiation
• external features: capsules and cell walls
• flagella for motility (not all species and not all the time)
  
  • eukaryotes use cilia: structurally and functionally different

Question 8

describe the cytoplasmic membrane in bacteria

Answer 8

structurally similar to that of eukaryotes

• lacks sterols (cholesterols)
  
  • hence need for cell wall (provides rigidity; gives cells their shape)
• bacterial membrane is functionally varied
• main roles:
  
  • selective permeability and transport
  • electron transport and oxidate phosphorylation (aerobes)
  • excretion
  • biosynthetic functions
  • chemotactic systems

Question 9

summarize the features and roles of the bacterial cytoplasmic membrane

Answer 9

Question 10

describe the peptidoglycan composition of the bacterial cell wall

Answer 10

• encloses cytoplasmic membrane and cytoplasmic contents
• defines cell shape
• high intracellular osmotic pressure would otherwise burst cell (lacks stabilizing sterols)

Question 11

name the 2 features that define gram staining character by cell wall composition

Answer 11

1. thickness of layers of peptidoglycan
2. cross-linking (type and extent)

Question 12

which 2 acidic polysaccharides are found only in gram positive cell walls?

Answer 12

• teichoic acid
• lipoteichoic acid

Question 13

describe the composition of the cell walls among the groups (bacteria, algae, protozoa, fungi)

Answer 13

Question 14

describe the steps of Gram staining

Answer 14

Question 15

gram positive bacteria have a ___ PG

while

gram negative bacteria have a ____ PG

Answer 15

Question 16

summarize the characteristic features based on Gram stain between Gram positive and Gram negative

Answer 16

Question 17

describe the linkage found in Gram positive

Answer 17

Question 18

describe the catalase test

Answer 18

• look for immediate oxygen bubbles; “fizzing”
  
  • bubbles = positive result
• useful for differentiation between Gram positive cocci:
  
  • • staphylococcus
  • • streptococcus

Question 19

list the medically important Gram positive pathogens

Answer 19

• catalase-positive
  
  • Staphylococcus aureus
  • S. epidermidis
  • S. saprophyticus
• catalase-negative
  
  • E. faecalis
  • E. faecium
• Lactococcus
• Streptococcus sp.
  
  • Streptococcus pneumoniae
  • S. pyogenes
  • S. agalactiae
• Viridans Streptococci

Question 20

describe features of the Gram negative outer membrane

Answer 20

• structurally and functionally different to cytoplasmic membrane
• chemically distinct
  
  • inner leaflet: similar to cell cytoplasmic membrane
  • distinctive outer leaflet
    
    • lipopolysaccharide (LPS)
    • outer membrane proteins
      
      • porins: enable passive diffusion of specific low molecular weight hydrophillic compounds
    • key control point for prevention of access by antibiotics

Question 21

name significant features of the lipopolysaccharide (LPS) layer

Answer 21

• role as physical barrier between G-ve bacteria and immediate environment
• recognized by the immune system: used to indicate presence of bacteria
• triggers inflammatory response
  
  • severe reponse to high levels of LPS: endotoxic shock
  • contributes to pathogenesis and associated clinical symptoms

Question 22

describe the structure of lipopolysaccharide (LPS)

Answer 22

Question 23

describe the function of porins in G-ve bacteria

Answer 23

• water-filled open channels that span outer membrane that allow passive diffusion of small hydrophilic molecules into cell
• important contributor to antibiotic resistance
  
  • changes or modifications to OMPs (outer membrane proteins)

Question 24

summarize difference between G+ve and G-ve based on cell wall

Answer 24

Question 25

describe mycoplasma sp. and mycobacteria

Answer 25

​exceptions to the G+ve and G-ve principles

• mycoplasma sp.
  
  • e.g. mycoplasma pneumoniae
  • lacks cell wall
  • has cellular membrane that contains sterols to provide rigidity
• mycobacteria
  
  • e.g. mycobaterium tuberculosis
  • waxy outer coat with high % lipids

Question 26

describe the linkage found in G-ve bacteria

Answer 26

Question 27

describe endospores

Answer 27

endospores are structures located inside the bacterial cell that are extremely resistant

Question 28

describe what is seen

Answer 28

Question 29

name 2 bacteria that can form endospores

Answer 29

bacteria that can form endospores include Bacillus and Clostridium

Question 30

summarize the components of an endospore

Answer 30

Question 31

contrast capsules and slime layers

Answer 31

both protect cell against dehydration; facilitate attachment to surfaces

• capsule
  
  • strongly attached
  • difficult to remove
  • highly organized
  • important for virulence: antiphagocytic
• slime layer
  
  • loosely attached
  • easily removed
  • relatively unorganized

Question 32

describe the location of bacterial flagella and descriptive term used to identify them

Answer 32

Question 33

name the species that have a built in endoflagellum

Answer 33

Question 34

describe the 2 component regulation system coordinated responses

Answer 34

• specific environmental signal detected by membrane bound receptor protein (e.g. histidine kinase)
• receptor facilitates transfer of phosphate group from cellular ATP onto appropriate response regulator (RR)
• RR can bind to specific sites on bacterial chromosome
• initiation of transcription and translation of genes for production of specific structure or enzyme