Gram Positive and Gram Negative Bacteria I and II Flashcards
describe the equation for CFU/mL
describe the 4 stages of bacterial growth
describe how turbidity can be used to assess bacterial growth
smaller size = better ___ to ___ ratio
smaller size = better surface area to volume ratio
substances enter and diffuse quickly
describe the association between arrangement and cell shape
describe cellular features unique to bacteria
- flagella for motility
- peptidoglycan cell wall
- capsule
- lipopolysaccharide (G-ve)
- type of communication
name features that are common to both G+ve and G-ve bacteria
- 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
- structurally slightly different in G+ve vs G-ve
- external features: capsules and cell walls
- flagella for motility (not all species and not all the time)
- eukaryotes use cilia: structurally and functionally different
describe the cytoplasmic membrane in bacteria
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
summarize the features and roles of the bacterial cytoplasmic membrane
describe the peptidoglycan composition of the bacterial cell wall
- encloses cytoplasmic membrane and cytoplasmic contents
- defines cell shape
- high intracellular osmotic pressure would otherwise burst cell (lacks stabilizing sterols)
name the 2 features that define gram staining character by cell wall composition
- thickness of layers of peptidoglycan
- cross-linking (type and extent)
which 2 acidic polysaccharides are found only in gram positive cell walls?
- teichoic acid
- lipoteichoic acid
describe the composition of the cell walls among the groups (bacteria, algae, protozoa, fungi)
describe the steps of Gram staining
gram positive bacteria have a ___ PG
while
gram negative bacteria have a ____ PG
summarize the characteristic features based on Gram stain between Gram positive and Gram negative
describe the linkage found in Gram positive
describe the catalase test
- look for immediate oxygen bubbles; “fizzing”
- bubbles = positive result
- useful for differentiation between Gram positive cocci:
- staphylococcus
- streptococcus
list the medically important Gram positive pathogens
- 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
describe features of the Gram negative outer membrane
- 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
name significant features of the lipopolysaccharide (LPS) layer
- 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
describe the structure of lipopolysaccharide (LPS)
describe the function of porins in G-ve bacteria
- 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)
summarize difference between G+ve and G-ve based on cell wall
