3-Bacteriology Intro Flashcards
viruses
general
smallest infectious particles
require host cell for replication
bacteria
general
prokaryotic unicellular org
-no nuclei or mem bound organelles
-1 circular chromosome + small ribosomes
-cell wall of peptidoglycan
-respiration @ cytoplasmic mem
fungi
general
more complex eukaryotes
-uni or multi cellular
20 um
parasites
general
most complex microbe
eukaryote
uni or multi cellular
how to classify bacteria
- fundamental features- visible, nutrition, end products, surface molecules
- 16S rRNA gene seq bc highly conserved
bacteria shapes
- coccus (singular sphere), diplococci (2), cocci clusters, cocci chain
- coccobacillus (oval)
- bacillus (rod), rod chain, curved
- spirochete (squiggle)
- spirullum (spiral)
bacteria structure
- cytoplasm- chromo + ribos + mRNA + proteins
- cytoplasmic membrane-lipid bilayer, ETC
- cell wall- peptidoglycan
- appendages- pili, flagella
- capusle- polysac or amino acids, protect from immune system
cell envelope purpose
permeability
-keep things in/out
-passage for water, nutrients
-either gram pos or neg
-cell membrane + everything beyond
gram positive bacteria
cell envelope
thick external peptidoglycan layer only plasma membrane
-has teichoic acid + lipoteichoic acid transmembrane to promote attach to other bacteria/host cells (PAMPS)
-lipoteichoic links PG layer to cell membrane
gram negative bacteria
- plasma/inner membrane
- periplasmic space
- thin peptidoglycan layer
- outer membrane- inner leaflet of phospholipids + outer leaflet of LPS + porins
gram stain steps
- crystal violet- permeates exposed peptidoglycan
- gram iodine- binds CV = complexes
- decolorizer- alc or acetone, dehydrates PG layer, traps complex in pos or washes complex away in neg
- safranin red- stains both grams but CV darker so pos = purple, neg = red
peptidoglycan layer
function
exclusive to bacteria = drug target
for 1. cell shape
2. structural support- flagella attach, prevent osmotic lysis
peptidoglycan composition
-alternating beta-1,4 sugars (NAG and NAM)
-parallel strands crosslinked by peptide sidechains on NAM but vary by species
immune effects peptidoglycan
- activate complement = his release > hypotension/edema, neutrophil chemotaxis
- macrophage activation (TLR4/CD14) = IL1/IL6 > fever, TNF-a > fever hypotension, NO > hypotension, tissue factor activation>coagulation (DIC)
LPS structure
lipolpolysaccharide
endotoxin with 3 subunits
1. lipid A- endotoxin activity so massive immune resp, anchored to outer mem by FAs
2. core polysaccharide- branched polysac 9-12 sugars
3. O antigen- long linear polysac of repeating saccharide units, species variation
LPS function
- protect from complement bc tight packed and neg charge for permeability, prevents MAC from getting past O antigen
- activates immune system binding CD14 and TLR4 on APCs > fever, inflamm, septic shock
mycoplasma
1 membrane
NO peptidoglycan or LPS
chlamydia
2 membranes
sometimes peptidoglycan
ehrilichia and anaplasma
cell envelope
2 membranes
NO peptidoglycan or LPS
mycobacteria and nocardia
cell membrane
1 membrane + peptidoglycan + thick waxy layer
acid fast staining steps
- staining red by carbol fuchsin
- decolorization
- counterstain with methylene blue
whatever is left red is the acid fast bacteria aka stain not removed by acid alcohol wash
acid fast examples
- mycobacteria
- actinomycetes
acid fast cell wall
lipid AND mycolic acid rich outer layers
-resist gram staining so require specific technique
-LAM to hold waxy layer to membrane
pili/fimbriae
proteinaceous hair like surface structures on various bacteria
does conjugation, motility, attachment
flagella
rotating helical structures anchored to plasma mem for motility
-can be on one pole, both poles, or everywhere
endospores
function
produced by gram pos bacteria to convert normal growing cell to a dormant state
- very resilient to pH, temp extremes, raditation, enzymes/chemicals
can germinate > single vegetative (growing) bacterium, og cell dies
endospore structure
dehydrated, multilayer structure
-has complete copy of chromosome + minimum proteins and ribos
endospore implications
- bioterrorism
- wide variety of environments
- exist for centuries
- need to be considered in sterilization, disinfection
