Them Bacteriaz Flashcards
bacteria are
single-cell organisms and prokaryotes
amount of chromosomes in bacteria
1 chromosome – can have more than one copy
size of bacteria
0.2-2 microns in diameter
two shapes of bacteria
cocci or bacili
cocci pair examples
pneumococci, meningococci, gonococci
chain cocci examples
streptococci
“grape like clusters”
staphylococcus
bacilli
rod shape of bacteria that varies in length
types of bacilli (rods)
square/rounded ends, short and rounded, tapered ends (fusiform), curved rods
hook shapes
vibros
prokaryotic nucleus
no nuclear membrane
prokaryotic division
no mitotic division
prokaryotic DNA
not associated with histones
prokaryotic organelles
no membrane-bound
prokaryotic ribsome size
70s
eukaryotic ribosome size
80s
types of storage granules
glycogen, PBHB, elemental sulfur, polymerized metaphosphate
plasmids
extrachromosonal DNA elements
bacteria that produce spores
bacillus and clostridium
bacillis
gram positive, rod shaped, obligate aerobe
clostridium
gram positive, rod shapes, obligate anaerobe
spores do not
undergo division, only germination (under favorable conditions will germinate and produce a single vegetative cell)
prokaryotic cell membrane
no cholesterol or sterols (EXCEPT mycoplamas)
mycoplasmas
cause primary atypical pneumonia
cationic dye added: bacteria stain
purple
add iodine
bacteria stain more purple
add ethanol/acetone
decolorization step, gram negative become decoloarized
counterstain
positive -> purple, negative -> pink
the more cross-linking of peptioglycan…
the more pigmentation
peptioglycan
polysaccharide with peptide cross links responsible for the structural rigidity of the cell, “sac like macromolecule” surrounding the entire cell
basic units of peptioglycan
NAG, NAA
peptioglycan sygar moeities
beta-1,4 linkage <– cleaved by lysozyme (saliva, tears, white blood cells)
peptioglycan crosslinking
via a pentaglycine bridge which is inhibited by penicillin
teichoic acids
found in gram positive organisms, repeating units of ribitol phosphate or glycerol phosphate joined through phosphodiester linkages, constitute major surface antigens of certain gram positive bacteria
wall teichoic acids
are attached to peptioglycan
membrane teichoic acids
attached to lipids embedded in the membrane
gram negative
outer membrane lipid bilayer composed of phospholipid and protein.
major antigenic determinants of gram negative bacteria
O-antigens (outer part of outer membrane that is anchored to the lipopolysaccharide)
endotoxin: gram negative
very important contributing factor to the severity of disease, lipopolysaccharide is the endotoxin of gram negative bacteria
space between the outer membrane and the inner membrane
perplasmic space and location for a number of hydrolytic enzymes or lysosomal-like enzymes present in gram negatives
lipid A
responsible for endotoxic activity of gram negative bacteria - virtually constant among gram negative organisms
presence of an O antigen
determines if the bacteria is “smooth” (as does a capsule), also important for serological typing “serotyping”
protoplasts
gram positive, mycoplasma, “bacterial persisters”
spheroplasts
gram negative, do no completely shed peptioglycan layer due to retention of the outer membrane
capsules
smooth, prevents pathogenic bacteria from phagocytosis, most are polysaccharides, K antigens (antigenic determinants)
bacillus anthracis capsule
made up of polyglutamic acid
flagella
not virulence factors, 3-12 microns, stain to see, locomotion, H antigens (serotype), flagellins, differences in aa primary structure
peritrichous
flagella all around the bacteria (vs. polar flagella on opposite sides)
pili
short hair like projections, protein in character, thinner and shorter than flagella, thought to be involved in adhesion,
F-pilus
special pilus used for conjugation (receptor for specific F phages)
definition of endotoxin
LPS component of gram negative bacterial outer membranes that is released at cell destruction or during normal growth cycles
definition of exotoxin
substance elaborated into the host tissues by a microorganism that causes damage to structure or function of affected target cells
definition of fibronectin
host cell surface associated glycoprotein that mediates nonspecific adherence of some bacteria (staph)
definition of pyogenic
stimulates the recruitment of polymorphonuclear white cells
definition of pathogenic bacteria
cause disease in the host…host inflammatory reponse
opportunistic bacteria
cause disease in immunosupressed, not healthy, people
barriers to entry
skin, ciliated epithelium, antibacterial secretions, mucin layer
pili and fimbriae
rod shaped protein structures, ordered array of single subunits, with tip structure that attached to host (usually carb residues)
adherence of bacteria occurs via:
pilli/fimbriae, afimbrial adhesins, biofilms
afimbrial adhesions
bacterial cell surface proteins that do not form pili, mediate binding to host (usually host proteins)
biofilms
ordered 3-D structures composed of pillars of bacteria surrounded by water channels, formed by bounding bacteria within polysaccharide slime, refractory to disinfectants and antibiotics
biofilms can…
be the source of aerosolized bacteria, can form on body surfaces/plastic tubing/plastic implants
iron
is essential to bacterial growth and is not found in its free form in humans (bound to transferrin/lactoferrin/ferritin/hemoglobin)
bacteria sequester
iron
bacterial sequester iron via
siderophores (low MW secreted compounds), binding to host proteins to sequester iron, toxins to kill host cells, iron abstinence
lyme disease causing bacteria
do not require iron for growth, use Mn as an alternate cofactor in non-dispensable enzymes
dealing with uptake via phagocytosis
1) prevent phagosome-lysosome fusion 2) degrade/form pores in lysosome membrane
phagocytosed bacteria can be killed by what host defense(s)?
NK cells, cytotoxic T-cell response
adaptation to live in a phagolysosome
producing enzymes that detoxify reactive oxygen species/prevent oxidative burst
phagocytes
immune cells with lysosomes
(Shigella or listeria) & actin
bacteria that grow in cytoplasm induce actin condensation to move to neighboring cells
shigella enters through
M cells
pathogenicity islands
cluster on bacterial chromosome of genes encoding virulence factors
hallmarks of pathogenicity islands
different CG content, near/within tRNA genes, encode virulence factors, acquired via horizontal gene transfer
virulence factor exams
adhesins, specialized secretory systems, toxins
horizontal gene transfer occurs via
transposons, bacteriophages
Type I Secretory System
one channel, span inner&outer membranes, no periplasm intermediates, one protein apparatus (usually); hemolysin
Type II Secretory System
general, inner membrane steps, periplastic intermediate, signal sequence (termini a), secrete virulence and non-virulent factors, cholera toxins
Type III Secretory System
one channel, span inner&outer membranes, several proteins, made to secrete virulence factors; “needle type”
“needle type” secretory system
Type III, injects virulence factors straight from bacteria to eukaryotic cytoplasm. result: changes cell signal transduction pathway causes inflammation, opening of tight junctions, electrolyte secretions, alteration on cytoskeleton; E.coli
Type IV Secretory System
span inner&outer membrane, several proteins, transfer bacterial DNA/effector proteins; “pili-type” structure; H. pylori
capsules
usually polysaccharides & occasionally proteins, protect against complement activation and phagocytes, some made with sialic acid or hyaluronic acid to mimic host cells
LPS
complement target in gram - bacteria,
LPS modification to change complement interaction
attach sialic acid to O-antigen (prevents C3 convertase formation), change LPS O-antigen length (prevents MAC mediated death)
exotoxins vs. endotoxin
exo found in gram - and +, endo in gram - only
exotoxin nomenclature is based on:
target, producing bacteria, activity, designated letter
the majority of bacterial toxins are encoded on
mobile genetic elements (bacteriophages) and plasmids (e.g. heat stable and heat labile toxins
type I toxins
bind to cell, not translocated inside; superantigens
superantigens
type I toxin, bind to MHC class II (macrophages), bind to T cell receptors (that bind to MHC), 1:5 T cells are stimulated by the binding of superantigens –> excessive cytokine (IL-2) release —> toxic shock (strep)
type II toxins
destroy eukaryotic membrane integrity; protein that forms membrane channels or an enzymes (phospholipase) that remove the polar head group of membrane phospholipids (s. aureus alpha)
type III toxins
A(=1) -B(>=1) toxins, A subunit has enzymatic activity, B subunit binds to host cell receptor (usually carb based), simple/complex toxins enter the cell
A-B subunits
type III toxins, usually separated by proteolytic cleavage but remain connected; A subunit is translocated into the cytoplasm, the B subunit determines toxin specificity
A subunit
removes ADP-ribosyl group from NAD, covalent attachment to host protein —> creates a variety of pathogenic downstream effects
