Microbial structure Flashcards
what do eurkarotes have?
nucelus bound by double membrane
linear DNA
DNA organised into chromosomes :complexed with proteins
large complex ribosomes , many types of rRNA and proteins
what do prokaryotes have ?
no nucleus , has nucleoid no physical boundary
circular DNA
plasmids present
70S ribsomes
what are the structural features of eukaryotes
cytoplasm filled with large complex collection of organelles
Mitochondria with cristae
transcription requires movement and formation of mRNA for translation
what are the structural features of prokaryotes
no membrane bound organelles independent of plasma membrane
mesosomes used in aerobic respiration
transcription and translation occur simultaneously
structural components of bacteria
capsule pili flagellae spores slime cell wall
what does the capsule in bacteria do
protects cell from phagocytosis , dessication
loose polysaccharide stucture
what do pili/fimbriae do
appendage for bacterial conjugation, forms tube to transfer plasmids between bacteria, attachement, facilitates bacterial attachement to host surfaces , lectin proteins
what do flagellae do
organs for movement
what are spores
hard multilayered coats, hard to kill, long term survival
what is slime
helps to bind lots of bacteria together in a biofilm which makes it hard to get to to treat with antibiotics, protects against immune attack
what is gram positive
purple , has 2 layers, thick layer of PGN with LTA
what is gram negative
has 3 layers, LPS lipopolysaccharide , thin PGM , pink
how does gram staining work
primary stain (purple), trapping agent , decolourisation
gram positive traps stain so stays purple
gram negative washes stain away
counter stain applied
what is PGN
peptidoglycan , mesh like layer
what is LTA
lipoteichoic acid , provides cell rigidity
what is LPS
endotoxins, potent immune and inflammatory host repsonses
how do bacteria replicate
they are self-replicating, reproduce by binary fission, bi-directional replication
4 phases of bacterial growth
lag, log/exponential, stationary, death
what is the lag phase
active cell growth (size), preparation for replication
what is the log phase
max rate of cell division,
stationary phase
exhaustion of nutrients,,rate of cell death is the same as new cells, cessation of growth
death phase
number of cells dying exceeds the number of new cells,
bacteria recombination
conjugation - transferring plasmids
transdution - exchange of DNA from bacteriophage
transformation - take up DNA from environment
how to class bacteria
gram stain, cell shape, atmospheric preference, key enzymes, fastitdiousness
