29. Bacterial Structure and Characteristics Flashcards
archaea vs bacteria
archaea: ancient, single cell, cell wall differences to bacteria, LACK PEPTIDOGLYCAN, no human pathogens
bacteria: NO NUCLEAR MEMBRANE, distinct biochem and RNA markers, asymmetrical membrane
structural components (fimbriae, capsule, flagellum), cell wall (gram + or -), and genetic makeup are three general ways to ____ bacteria
classify
obligate aerobes _____ oxygen
require
microaerophiles ______ oxygen
require reduced
obligate anaerobes _____ oxygen
require no
facultative anaerobes ____ oxygen
they are anaerobic or aerobic
capnophiles _____ oxygen
require INCREASED CO2
what are 6 general levels we use to classify bacteria?
- shape
- gram reaction
- atmosphere
- spores
- biochemisty/genetic classification
- serology typing
what shape to staphylococci make?
like grapes
what shape to vibrio make?
like a comma
what shape do Bdellovibrio make?
comma with a tail
what shape do borrelia burgdorgeri make?
corkscrew
what shape does syphilis make?
spirochete
what shape does helicobacter pylori make?
helical
what shape are palisades?
bacili lined up in columns
are cocci normally gram - or +?
+
are bacilli normally gram - or +?
-
what is a red blood plate vs a chocolate blood plate?
RBCs intact in red, RBCs popped in chocolate (see iron)
what do alpha bacteria do on a red blood plate?
start to get conversion of hemoglobin to methemoglobin so turns brown
what do beta bacteria do on a red blood plate?
complete hemolysis - no RBCs around bacteria
what do gamma bacteria do on a red blood plate?
nothing
what 4 structures are common to all bacteria?
cell membrane/envelope
cytoplasm
ribosomes
one (or a few) chromosomes (eg E. coli technically has one but the chromosomes replicate at a different rate than the cell can divide so often find multiple in one cell)
layer number for each:
gram +
Gram -
acid fast
gram + (2 layers)
- cell wall (peptidoglycan)
- cytoplasmic membrane
gram - (3 layers)
- cytoplasmic membrane
- cell wall
- outer membrane
acid fast bacteria (2.5 layers)
- cytoplasmic membrane
- cell wall
- acyl layer
gram + cell wall structure?
- thick peptidoglycan cell wall (40+ layers)
- resists lysis by complement
- teichoic acids and lipoteichoic (LTA) polymers
- other proteins and carbs (enzymes/adhesions)
- TLR2 recogntion (LTA)
- inner membrane has 2 leaflets and is symmetrical, outer is NOT
gram - cell wall structure?
- asymmetric outer membrane (outer leaflet composed of LPS, inner leaflet of peptidoglycans)
- thin peptidoglycan layer
- periplasmic space b/w membrane (aqueous)
- barrier to non-polar molecs
- outer membrane porins (nable diffusion across outer membrane, barrier to large polar molecs)
- TLR4 recognition (LPS)
acid fast cell envelope?
- most similar to gram-positive cells (mycobacteria…so hard to treat thanks to the novel molecules in its membrane)
- cell wall comprised of fatty acids and waxes
- lipid components difficult to stain but once stained, stay stained
- mycolic acid, WAX D (much more rigid), arabinogalactans and sulfolipids present in cell wall
- TLR1/2/6 recognition
steps to gram stain?
fixation - crystal violet - iodine treatment (crosslinks peptidoglycan to change it from porous to tight closed so that gram+ retains violet) - decolorization - counter stain safranin (red)
what pathogens have acid fast cell wall?
mycobacterium
acid fast staining procedure?
- stain with carbolfuchsin
- resists decolorization with acid alcohol
- counter stain with methylene blue
peptidoclygan cell wall is unique to what?
prokaryotes
the peptidoglycan is what?
polymer consisting of 2 sugars and 5 aa’s that forms a mesh-like layer outside of the cytoplasmic membrane
- gives strong structural support (gram + thick, 90% dry weight; gram - thin, 10% dry weight)
- rigid (protects vs osmotic pressures)
- involved in bacterial replicatoin
- TARGET OF MANY ANTIBIOTICS
sugars of the peptidoglycan prokaryotic cell wall?
NAG and NAM (alternating)
they make up the backbone and they are cross linked by peptides and there are tetrapeptide cross chains to keep Nag and Nam together
gram + amino acids of NAM/NAG peptidoglycan monomer?
L-alanine D-glutamine L-lysine D-alanine D-alanine
gram - amino acids of NAM/NAG peptidoglycan monomer?
L- alanine D- glutamic acid meso diaminopimelic acid D-alanine D-alanine
what makes the aa’s pentapeptide of the prokaryotic peptidoglycan unique?
has D-forms of aa’s that do not occur in human proteins and are thought to help vs attack by peptidases
enzymes required for peptidoglycan synthesis?
transglycosylase (inserts and links new peptidoglycan monomers)
transpeptidase (forms the peptide cross-links between the rows and layers of peptidoglycan) *** common target to keep bacteria from replicating
bacterial motility with flagella - forward vs backward motion
anticlockwise rotation: forward movement, swimming (chemoattractant)
clockwise rotation: tumbling movement, reorientation
flagella are present on which types of bacteria?
bacilli and spirochetes, but not cocci (so don’t see on gram +, ie never see staph and strep w/flagella)
3 parts of flagella?
filament, hook (sheath), and basal body
what is a single flagella called- what is an example?
monotrichous (vibrio)
what are multiple flagella from one spot called?
lophotrichous
what are one flagella from each end called?
amphitrichous
what are many flagella in multiple directions called - what is an exam?
peritrichous (E.coli)
pili/fimbriae are present on gram+ or gram- bacteria?
both
what motility is afforded thanks to fimbriae?
twitching motility - grappling hook (type IV)
gives adhesion to surface and each other
fimbriated strains of E.coli can do what to RBCs?
agglutinate
how are pili used in bacterial sex?
exchange of genetic material = CONJUGATION
are fimbriae or pili longer?
pili
do gram+ or gam- bacteria have glycocalyx?
both
what is the purpose of the glycocalyx?
helps the cell adhere ot the env’t (biofilm) or is a virulence factor
and protects bacteria from phagocytes - keeps macrophages at arm’s length, looks like host, and really big for macrophages to engulf
slime layer vs capsule glycocalyx?
slime layer: loosely assoc with the cell
- protects from dehydration and loss of nutrients
capsule: firmly attached to cell wall (so doesn’t slough off)
- gummy, sticky consistency
- protects similar to slime layer
- adhesion to surfaces and nutrients
endospores are found in gram+ or - bacteria?
certain gram+ (bacillus and clostridium)
what is the endospore?
a dormant, tough, and temporarily non-reproductive structure
- resistant to extreme heat/radiation but can be destroyed by autoclave or burning
- mult layers
- when env’t returns favorable,it can germinate itself
some have crystals of nutrients too
classes of plasmids?
fertility plasmids - conjugation
resistance plasmids - resistance vs antibiotics
col plasmids - contain genes that code bacteriocins that kill other bacteria
degradative plasmids - digestion of unusual substances
virulence plasmids - turn bacterium into a pathogen
