three parameters of microscopy
magnification
resolution
contrast
light microscopy
visible light passes through a series of lenses to produce a magnified image (~1000x)
bright field
most common
illuminates field evenly
phase contrast
amplifies slight variations in refractive index
can be live samples
fluorescence
use a dye to tag to illuminate structures
electron microscopy
electron beams are used in place of light, can clearly magnify images 100,000x (can not be living cells)
transmission electron microscopy
cross sections
cell structure details
scanning electron microscopy
3D view
cell surface details
atomic force
a probe moves in response to the slightest force between it and sample
greater resolving power than EM
surface details
coccus
circle
bacillus
rods
vibrio
curved rod
spirillum
shorter, rigid, external flagella
spirochete
longer, flexible cell wall, endoflagella
groupings of cells
depends on the plane which they divide
differential staining
distinguishes between two groups of bacteria
gram positive
remain purple
thick peptidoglycan layer
teichoic acids (negatively charged)
gel-like between peptidoglycan and membrane
gram negative
counterstain pink
think peptidoglycan layer
outer membrane: porin proteins and LPS
periplasm between inner and outer membranes
peptidoglycan
specific to bacteria
permeable to sugars, amino acids and other substances
LPS (outer membrane in gram negative)
o antigen is recognized by the immune system
lipid A acts as an anchor
penicillin
antibiotic
inhibits cell wall synthesis by preventing glycan chain cross linking
gram negative generally more susceptible
lysozyme
enzyme
breaks down the of the glycan chain (tears and saliva)
gram positive is more sensitive
acid fast staining
small group of microbes
waxy cell wall do not gram stain
cells that retain the primary red stain are "acid fast"
tuberculosis and leprosy diagnosis
mycoplasma
lack a cell wall
vary in cell shape
stronger membrane (contain sterols)
archaea
no peptidoglycan
single membrane
s-layers (surface layers): sheets of protein or glycoprotein
eukaryotes
diverse cell walls
algae cell walls
polysaccharides (often cellulose or pectins) or even silica or calcium) - diatoms
fungi cell walls
polysaccharides (chitin) and glycoproteins
cell envelope
membrane, cell wall, capsule (if present)
capsule:
distinct and gelatinous
slime layer
diffuse and irregular
flagella
long protein structures used in most prokaryotic mobility
in bacteria, they spin like propellers
powered by proton motive force
eukaryotic flagella
powered by ATP
under plasma membrane
microtubules and motor proteins (cytoskeleton)
movement is whip like
pili
shorter and thinner than flagella
similar structure (protein subunits)
different function
cytoplasmic membrane
selective barrier
anchors proteins
energy transformation
hypotonic
water flows in
hypertonic
water flows out
passive transport
rare in bacteria
from area of high concentration to low concentration
active transport
against concentration gradient
need energy input
important in bacteria
proton motive force
electrochemical gradient of H+ (protons)
source of potential energy
group translocation
transported molecule is chemically modified
energy from an organic compound is used to drive transport
no longer transported in the other direction
can help cell monitor how much transported molecule there is
secretion
protein secretion is directed by a specific amino acid tag or signal sequence
chromosome
single, circular, double stranded DNA
tightly packed and super coiled
found in nucleoid
ribosomes
site of protein synthesis (translation)
similar: made of proteins and RNA, 2 subunits, but different in eukaryotes: size, sequence
cytoskeleton
less extensive than eukaryotes, but homologous
less is known
cell division and cell shape
storage granules
accumulate and store large carbon polymers or other nutrients (glycogen or phosphate)
gas vesicles
aquatic bacteria
protein bound compartment that provides buoyancy
controlled density
endospores
differentiated cells produced by some bacterium
very resistant to heat, chemicals, radiation
formed during a distinct phase of growth (sporulation) and cued by environment
germination
back to vegetative growth (spores)