PID BLOCK3- bacteriology Flashcards
Ribosomes
- ribonucleoproteins w large 50s and small 30s subunit
- protein synthesis + translation
-target for antibiotics
- 16s rRNA gene encoding for 30s subunit used for reconstructing phylogenies
Plasma membrane
inner membrane next to cytoplasm
-PHOSPHOLIPID BILAYER + PROTEINS
-where energy is stored
Proteins in the plasma membrane
- Transport proteins
- Energy generation components
- Proteins that anchor or help assemble
Transport proteins
- in the plasma membrane
-transport of specific molecules in and out of cell
- mediates passage of hydrophilic substances
Energy generating components
synthesis of ATP in plasma membrane
Phospholipid bilayer
Part of plasma membrane
-hydrophobic/hydrophilic sides
-Hydrophobic/ lipid solube can pass with passive diffusion
Main functions of plasma membrane
- Selective permeability barrier
- Bacterial respiration and energy generation
- Anchor for external structures
Cell wall
PEPTIDOGLYCAN LAYER
-mesh like structure containing alternating subunits of NAG and NAM cross-linked w peptides by transpeptidase enzymes called Penicillin binding proteins (PBPs)
Peptidoglycan
Bacteria cell wall, good target for antibiotics
polymer unique to prokaryotic cells
Penicillin- binding proteins
PBPs
- transpeptidase enzymes that connect with NAG and NAMs in cell wall
Function of cell wall
- Protection against mechanical damage and osmotic lysis
- Transport: non selective permeability
Outer membrane
- Only in Gram neg bacteria
Protein containing asymmetrical lipid bilayer (LIPOPOLYSACCHARIDE or endotoxin)
Function of outer membrane
Only in gram neg
- Selective permeability
- Resistance to large or hydrophobic toxic compounds
- Tolerance to detergents + bile salts
Lipopolysaccharides
- in the outer membrane of gram neg bacteria
-virulence factor
lipid A component = endotoxic activity
Mediator of septic shock
heat stable
Symptoms of LPS
- Fever
- Leukopenia
- Anorexia
- Diarrhea
- Blood coag
- Hemorrhagic shock
The exceptions to the 2 main structural classes of bacteria are?
Mycobacteria and Mollicutes (mycoplasma)
Mycobacteria
Bacterial envelope is gram + but contains MYCOLIC ACID
-Acid fast staining for identifying
Mollicutes (Mycoplasma)
Plasma membrane w sterols
NO CELL WALL- no peptidoglycan layer
Capsule
POLYSACCHARIDE LAYER
Function of the capsule
- Protection
- Virulence factors
- Nutrient reserve
Endospores
- Cryptobiotic state of dormancy, most durable
-Produced by Bacillus and Clostridium
-keratin spore coat helps survival
Function of endospores
- Ensure survival during adverse enviro conditions
- Dormant, highly resistant bodies
Flagella
-on bacterial surface
Flagella function
locomotion or bacterial motility
Pili/Fimbriae
- Fine, straight hair-like, attached to cell wall
- Most common on Gram neg bacteria
for adhesion
Function of pili/Fimbriae
- Adhesion to host tissues
- Contribute to antigenicity
Bacterial colony
single bacterium multiplies on solid growth media.
Growth of bacteria produces a colony that is visible without microscope
Different morphology depends on
Culture medium
Incubation time
Temp
Oxygen
Genetic differences
Environmental factors of bacterial growth
- Nutrients
- pH (best growth @ 7.2-7.4)
- Ionic strength + osmotic pressure
- Light
- Temp (most are mesophilic w growth at 30-37 C)
- Gaseous requirement: O2 or CO2
Classification of bacteria based on O2
- Obligate aerobes
- Obligate anaerobes
- Facultative anaerobes
- Aerotolent anaerobes
Generation time
time required for a single bacterial cell to yield 2 daughter cells (30 min- 20 hrs)
How do bacteria replicate?
Binary fission
Bacterial growth curve
- Lag phase
- Exponential phase/ logarithmic phase
- Maximal stationary phase
- Decline phase/ death phase
Lag phase
cell size increases
active metabolism but no division
Exponential or Logarithmic phase
cells multiply at maximum rate
Maximal stationary phase
Due to exhaustion of nutrients or toxic byproducts
Growth is ceased
Fungal characteristics
- Eukaryotic
- Non-photosynthetic heterotrophs
- Aerobic growth
Cell membrane contains sterols (ergosterol) and chitin
Mycelium
filamentous mass of hyphae
Convalescent carrier
recovered but continues to shed pathogen
Ex: strangles in horses
Incubatory carrier
incubating pathogen but not yet ill
shedding of pathogen during incubation period
Strangles in horses
- detection of convalescent carriers
- contagious febrile disease of URT w abscess of lymph nodes
Pathogenicity islands
carry genes coding 1 or more virulence factors
- horizontal gene transfer
- mobile, located on bacterial chromosome or plasmids
Quorum sensing
regulates gene expression in response to changes in cell density
Mediated by chemical signal molecules (autoinducers)
Low density= individual cell behavior
High density= group behavior
makes biofilm
Virulence factors that play a role in adherence
- Flagella
- Pili/ Fimbriae
- Capsule= glycocalyx.. layer of exopolysaccharides
Invasion
ability of pathogen to spread to other locations in host by invading host cells/tissues
Extracellular invasion
breaks down barriers of tissue to disseminate in host while remaining outside host cell
Production of extracellular enzymes
Intracellular invasion
bacteria penetrates cell and survives within enviro
- Facultative intracellular
- Obligate intracellular
Exotoxins
Proteinaceous toxins
Delivery by:
1. Secretion into milieu
2. Direct injection into host cell
Type 1 Exotoxin
- Active @ cell surface
- Disturbs cell metabolism by binding to receptors on cell surface
Ex: clostridium perfringens
Type 2 Exotoxin
damages membranes of cells
Ex: staph aureus
Type 3 Exotoxin
Intracellar, needs transport protein to be brought in (A-B toxins)
Ex: clostridium botulinum
Types of proteolytic toxins?
- Botulinum toxin
- Tetanus toxin
Endotoxins
component of prokaryotic cell wall, not released until cell death and lysis of bacteria
Effect: fever, diarrhea, weakness, blood coag, septic shock, death
(Lipo) Teichoic Acid
Only in GRAM +
Mediator of septic shock
Does exotoxins have low or high toxicity?
High toxicity
Do endotoxins have low or high toxicity?
Low toxicity
Where is the gene location for exotoxins vs endotoxins?
Exotoxins= on plasmids
Endotoxins= on bacterial chromosome
Heat stability for exotoxin vs endotoxin?
Exotoxin= heat labile
Endotoxin= heat stable
Are vaccines available for exotoxins or endotoxins?
Only available for exotoxins (toxoids)
Antigenicity of exotoxin vs endotoxin
Exotoxin= highly antigenic
Endotoxin= poorly antigenic
What species are exotoxins found in?
Both gram positive and gram negative
What species are endotoxins found in?
Mostly gram neg and Listeria
True or false: Endotoxins are part of the cell wall
TRUE
What is the protein location of exotoxins?
Proteins secreted from cell
Biofilms
Mass of bacteria, clings to surfaces
Produces extracellular polymer matris and exchanges nutrients
Functions of biofilms
- Bacterial persistence (endocarditis)
- Reduc. of host immunity
- Local damage (Ex: catheters)
- Reduced susceptibility to antibiotics
Iron uptake
needed for bacterial growth
Bacterial cytotoxins damage host by releasing ferritin, hemoglobin, lactoferrin
Receptor mediated recognition
