intro L1-11 Flashcards
light microscope res and mag
200nm res
*1000 mag
types of light microscopy
brightfield (standard)
darkfield (^contrast no stain)
phase contrast (refraction/ interference)
DIC (differential interference contrast)
fluorescence
types of scanning electron microscopy
confocal (laser to scan multiple z-planes)
2 photon (long wavelength light)
gram-staining process
- add primary crystal violet stain
- iodine application (mordant)
- wash w alcohol (decolorizer)
- safranin application (counterstain)
gram negative
outer-membrane
less peptidoglycan
e.g. e.coli
gram pos
thin peptidoglycan layers
no outer membrane
bacterial cell wall functions
protection
target
cell division
cell shape
GFP
green fluorescent protein
good for live imaging, simultaneous visualization of various,
misleading malfunction
bacterial S layer
outermost layer
crystalline lattice of single protein
protective selective sieve
lost in lab strains often
capsules
polysaccharide
sometimes covalently attached to cell wall
biofilms importance > can be immunogenic
immune response avoidance
pili and fimbriae
protein polymers
attachment/ adhesion
pathogenesis / immunogenic
support conjugation
“twitching” motility
pili longer and fewer
chemotaxis
directionality
flagella
bio nanomachine w rotary motor
endospores
starvation triggered
v resistant
germinate under conditions
survival mechanisms
biofilms
communities
held by matrix
often differentiate
promote adhesion and resistance
phases of batch growth
lag
expon
stationary
death
lag phase
condition adjustment
metabolic enzyme/ metabolite synthesis
expon phase
optimal growth
stationary phase
rate of cell production = rate of cell death
growth limit by nutrient depletion/ toxin accumulation
death phase
complex viability loss w some cell turnover
growth measurement methods
plating
turbidity
direct microscopic counting
flow cytometry
plating methods
“colony forming units” extrapolated for cell numbers
:) of plating methods
v sensitive
customization for species of interest
only viable cells
:( of plating methods
underestimates for cells in chains/ clusters
no. dependent on growth conditions
turbidity method
measures light scattering by cells
:)/ :( of turbidity method
:)simple
convenient/ continuous
non-destructive
:(measures dead cells
decreasing sensitivity
accuracy affected by culture turbidity
:) direct counting method
direct
clumping/ chaining accomodation
:(
laborious
can’t distinguish live/dead
flow cytometry
measures particles in a microfluidic flow
:) flow cytometry
automated
measures fluorescence at multiple wave-lengths
cell sorting
FACS
Fluorescence Activated Cell Sorting
:( equipment required
cell splitting in binary fission
septum forms at mid-cell as Z-ring constricts
replisome
DNA replication machinery
replication fork
structure formed as DNA is replicated
chromosomes replication
replisomes bind to oriC
bidirectional replication to ‘terC’
chromosomes segregate and cells divide
bacterial chromosome replication time
~40 mins
1000bpm
why do b.subtilis and e.coli divide every 20 mins?
as they initiate replication in previous cell cycle
daughter oriC’s location on chromosome
1/4 or 3/4 distance along cell
divisome
governs septum formation/ cell division
assembles into Z-ring
cyanobacteria differentiations
heterocysts > N2 fixation
akinetes > survival
B. dellovibrio
grows inside other bacteria
myxococcus
eats other bacteria and complex fruiting bodies
catabolic vs anabolic
energy releasing/ energy building into food
macronutrients
proteins
lipids
carbohydrates
nucelic acids
two types of nutrient media
chemically defined
undefined ‘complex’
bacterial monitoring measurement and calculations
measures population density and number
calculates growth rate and generation time
cell count formulae
N=N(0)2^n
final cell number= initial cell number*2^(no. generations)
g=t/n
generation time= expon growth duration/ no. generations
factors affecting growth of bacteria
temp
pH
osmolarity
O2 availability
chemostats
bioreactors
open system in which fresh media is added whilst spent media removed
chemostats advantages
growth at “steady state”
important in bioprocessing
dilution rate
flow rate/ volume
mu
growth rate relating to slope
flow rate and growth rate relation
if flow> growth rate - wash-out
if flow < growth - stationary phase/ wash out
microfluidics
agar pad w tracks whilst SEM observes individuals
silicon master
bacterial DNA
v condensed
4.6 mbp
3 micrometers
not double-membrane bound
E.Coli chromosome
circular
operons
gene clusters transcribed together
densely-packed genes
bacterial DNA mobile elements
plasmids
antibiotic resistance genes
transposable elements
conjugation plasmid
small extrasomal DNA strand
shigella
E.Coli related
causes dyssentry
plasmid pINV encodes key virulence genes
types of bacteriophage
lytic
lysogenic
transduction
transposons
jumping genes
often resistance
integrons
accumulate ‘useful’ genes
bacterial genome variation
core > “housekeeping” genes
accessory > mobile elements inc
pangenome
totality of genes across all strains of a species
implications of genome sequencing
epidemiology of infectious disease
comparative genomics
understanding bacterial genetic
uncovering unsampled diversity
changing classification of organisms
metagenomics
art
illumina genome sequencing
highly scalable
short DNA fragments
sanger genome sequencing
slow / expensive
accurate
sequence assembly
overlapping sequences aligned
complete genome assembly
oxford nanopore
v long reads
:( less accurate
bioremediation
use of microorganisms, plants or enzymes to detoxify soil contaminants (as xenobiotic pollutants resistant to natural degradation)
biotechnology
cellular factories
organisms producing medically/ commercially useful biomolecules
quick/ cheap
genetic modification of bacteria
clone gene of interest into expression vector > linearise > ligate > transform> multiplication> lysis and purification and induction
recomb therapeutics + enzymes
small-scale, high value products or high volume, low-cost commodities