Medical Micro - Bacteriology Flashcards
what are the 2 types of bacterial cells
gram +
gram -
difference between bacteria and archaea
lack peptidoglycan in cell walls
mostly studied in extreme environments
have different types of lipids in their membrane
features of crenarchaetoa and where do they reside
Thermophilic & hyperthermophilic.
Cool marine planktonic waters
features of euryarchaetoa
methanogens
Halophiles
Thermoacidophiles
what do methanogens do
use H2 to reduce CO2 to CH4
where do halophiles reside
Halophiles – live in very high salt environments
what are optimum conditions for thermacidophiles
have an optimum growth temperature between 60 – 80C
live at low pH
what are protozoans
protista
eukaryotic cell
where do protozoans inhabit and what do they consume
water and soil
feed on bacteria and small particles
how do protozoans reproduce
sexually and asexually
how do protozoans consume their food
absorb nutrients through their membrane or wrap themselves around their prey to ingest
what is the size range of a protozoan
2μm - 2mm
what is a virus
Obligate intracellular parasites – cannot replicate by themselves
what kingdom do virus belong to
no kingdom
how is information organised within a virus
ds DNA, ss DNA, ds RNA, ss RNA – usually organised as single linear or circular molecule of nucleic acid.
structure and function of the caspid
protein subunits
protects the nucleic acids
what is marine snow
loose association of microbes with organic detritus
what are pellicles
predominantly 2D structures forming on surface of liquids
what is step 1and 2 of biofilm formation
adhesion
reversible and irreversible
what is step 3 of biofilm formation
maturation 1
formation of microcolonies surrounded by EPS
what is step 4 of biofilm maturation
maturation 2
formation of a continuous biofilm
what is step 5 of biofilm formation
dispersion and sloughing off
due to programmed cell death, lytic phage expression or NO signalling
what is step 6 of biofilm formation
transport of biofilm particles
dispersed organisms phenotypically similar to planktonic cells
what is EPS
extracellular polymeric substance
house of biofilm
list biopolymers of microbial origins
polysaccharides
proteins
glycolipids, phospholipids, LPS
nucleic acids
what does bacterial biofilm act as
a major barrier to wound healing
outline initial reversible adhesion
adhesion at a distance of 5-20nm
little energy needed to remove bacteria
outline irreversible adhesion
binding is mediated by polymer bridging - achieved by reduced radius of body
irreversible binding
specific receptor/adhesion process
achieved by bacteria but not colloids
outline the structural function of peptidoglycan
forms sheets around the cell - connected by cross links to form a polymer
can be 90% of gram-positive cell wall
in gram-negative bacteria what is used as an effective bacteria
lipopolysaccharide layer
LPS
what is the purpose of understanding the differences of gram-negative/positive cell walls
important for targeting bacteria
many antibiotics are effective in targeting gram-positive bacteria but show little specificity for gram-negative bacteria
in terms of microbial locomotion what is the purpose of gas vesicles
allow regulation of position in water column for some aquatic species
what are some forms of bacterial motility except flagella
twitching
gliding
swarming
what are the 3 main morphologies of dsDNA phages
myophage
siphophage
podophage
what allows phages to have different specificity
absorption apparatus
what is rigid body motion
rotation of the phage that allows it to inject genetic material into the host
what is reversible absorption
first contact of the phage with the receptor on the cell surface
what is irreversible absorbtion
phage walks on the cell surface to find a spot to absorb irreversibly
AKA moon walk
how does long flexible ejection system work
the phage uses a screw like mechanism that reaches the host cytoplasm
how does viral contractile ejection system work
the phage docks and ejects genetic material into the host cytoplasm
what is the difference between lytic and lysogenic phages
lytic - replicates phages and kills cell
temperate - introduces viral genetic material into host genome
functions of endolysins/holins step 0
lytic protein accumulation
step 1 of endolysins/holins function
inner membrane disruption
step 2 of endolysins/holins function
peptidoglycan disruption
step 3 of endolysins/holins function
outer membrane fusion with inner membrane
what is the lysogenic cycle
phage inserts its viral genetic material into host genome
does not kill the host - initially
how do temperate phages decide between lytic or lysogenic
lysogenic - low amount of host compared to phages
lytic - abundance of hosts to infect
phages communicate to each other to decide
what is the pseudo-lysogenic cycle
phage infects a cell that does not want to divide
phage remains in the cell as a molecule
only one of the daughter cells carries phage DNA
step 1 for capsid formation in the cell
terminase binds viral genome
step 2 of capsid formation in the cell
terminase-DNA binds procapsid portal
step 3 of capsid formation in the cell
DNA translocation
step 4 of capsid formation in the cell
contamer cleavage and packaging completion
what are different antiviral resistance methods
preventing virus absorption
preventing virus DNA entry
cutting virus nucleic acids
abortive infections
how is virus absorption blocked
the host can mutate or mask its receptors
phage cannot undergo irreversible binding
how do phages bypass receptor masking by EPS
phages produce EPS degrading enzymes
what is superinfection exclusion
when a virus infects a host cell and commands the cell to not allow other viruses to enter
how is superinfection exclusion mechanism achieved
expression of:
Imm - redirects DNA outsides
Sp - blocks T4 lysosome
how is cutting virus nucleic acids mechanism acheived
host DNA is protected from cleavage, viral DNA is not
i.e. methylation
how can phages bypass virus nucleic acid cleavage
modify nucleotides, makes it bulkier
enzymes cannot reach nucleic acids to cleave it
how is the abortive infection mechanism achieved
Phage DNA replication is detected by RexA
activated RexA activates RexB
RexB allows escape of +ions
membrane potential is lost and ATP synthesis is blocked
