Bacteria Morphology Flashcards
virus replication cycle
Attachment
Penetration
Uncoating
Transcription
Translation
Genome replication
Assembly
Release
characteristics of bacteria
no membrane-delimited nuclei
cytoplasm is gel-like
not homogenous
DNA replicates semi-conservatively
genome attached to cell membrane
one or two circular chromosomes
translation in bacteria
large and small ribosomal subunit
IF1, IF2 initiation factors
initiation: mRNA binds small ribosomal subunit with Shine Dalgarno sequence (AGGAGG)
requires energy
occurs in cytoplasm
what does no nuclear membrane allow for
simultaneous transcription and translation
what kind of cell membrane do bacteria have
lipid bilayer
plasma membrane
a selective barrier
limit the free-diffusion of ions
most polar compounds must be specifically transported across the membrane by proteins
transport against a concentration gradient requires
energy
why is membrane potential essential to generate energy
proton motive force
electrical potential does work:
generate ATP, turn flagella, move solutes
what does the cell wall do
maintains structure
surrounds cell protoplast
prevents osmotic lysis of cell protoplast
types of solutions
isotonic: same solute concentration, no net movement of water particles
hypertonic: has a higher solute concentration than another solution, particles move out of cell (crenation)
hypotonic: solution has a lower solute concentration than another solution, particles move into cell (lyse)
peptidoglycan
gram + structure VS gram - structure
made of peptides and glycans
gram+ structure contains pentapeptide and tetrapeptide between NAG and NAM
gram- structure has a direct link between NAG and NAM
gram staining
if there is a thick peptidoglycan layer (gram+) the colour stays in (purple)
porins
create pores in outer membrane
mainly in gram- bacteria
homotrimers
small channels allow for passage of small solutes
antibiotics can pass through
lipopolysaccaharide (LPS)
an endotoxin
only in gram-
very stable
reduces blood pressure
septic shock
lipoteichoic acid
gram+ only
covalently link to peptidoglycan
negative charge and hydrophobic site
antigenic
mycobacteria have
an additional mycolic acid and arabinogalactan layer
mycoplasma
has no cell wall
requires a isotonic environment
can cause respiratory disease
capsules
a glycocalyx around the cell wall
sugar coat (polysaccharides)
promotes adhesion
limit permeability (negative staining with dyes)
inhibit phagocytosis
nutrient reserve
enhance pathogenicity
endospores
nutrient limited conditions
very stable
keratin-like coat
resistant to UV, heat, dessication, antibiotics, disinfection
sporulation
DNA replicates
membranes around DNA
forespore
protective cortex
protein coat
spore is released
germinate (enzymatic digestion of coat, growth)
how are endospores associated with disease
harmless themselves until they germinate, involved in many human diseases; tetanus, botulism, gas gangrene
flagella
motility
require membrane potential (proton motive force)
60 cell-lengths/sec
antigenic and a PAMP
flagella arrangements
monotrichous
amphitrichous
lophotrichous
peritrichous
flagella rotation
running: bundled flagella (counter-clockwise rotation)
tumble: flagella separated (clockwise rotation)
attractant: chemical gradient (tumbling or running)
