lecture 2 bacteria 1 Flashcards
what are the three domains of life?
bacteria
arcaea
eukarya (protists, fungi, molds)
whats the most powerful microscopy tool?
xray crystollography
what are 4 morphologies of microbes and which are most common?
filamentous rods
rods
spirochetes
cocci in chains
common: rods and cocchi
what are the general features of a typical bacterial cell?
cell membrane
chromosomal dna that is concentrated in a nucleoid and extrachromosomal dna called plasmids
ribosomes
cell wall
some prokaryotic cells may have flagella pili fimbriae and capsules
differences between flagella, pilus, and fimbriae
flagella is for motility
pilus is for flexibility, four types, can be rigid
fimbriae are shorter more flexible and made of sugar. used to colonize and stick bacteria together or to surfaces.
what are the 5 functions of membrane proteins?
integral or peripheral proteins
transport
osmosis
energy
sensing
secretion
what is a hopanoid
chemical structurre of these are diverse but the role is the same as cholesterol as stabilizing agent for the membrane of bacteria
three functions of cytoplasmic membrane?
permeability barrier - prevents leakage and is gateway for transport of nutrients/waste into and out of the cell. polar and charged molecules must be transported.
protein anchor - holds transport proteins in place
energy conservation - generation of proton motive force
what are four types of lipids
cardiolipin
palmitic and oleic acid
cyclopropane fatty acid
hopanoids
describe function of cardiolipin
palmitic and oleic acid
cyclopropane fatty acid
hopanoids
cardiolipin= binds environmental stress proteins when the cell is under osmotic stress
palmitic= add fluidity to membrane in cold temperatures, saturated or unsaturated
cyclo= stiffens cell membrane by converting unsaturated fatty acids to cyclopropane
hopanoids= stabilize membranes like cholesterol does
how do prokaryotes protect the cell membrane?
cell envelope includes at least one structural supporting layer like the cell wall, helps keeps its shape and resist mechanical stress
describe gram positive bacteria
thick cell wall
describe gram negative bacteria
thin cell wall
how does cell wall protect against changes in osmotic pressure
because cell membrane is typically attached to the cell wall (which is s rigid sugar protein coat) which allows it to maintain its shape in different solutions
describe the structure of the cell wall
consists of a single interlinked molecule, like a mesh that is made up of peptidoglycan - 100 of them have been distinguished
long line of sugars ties together by beta 1,4 linkage
those sugars are tied through bridges of amino acids
that bind creates the mesh
what is the rigid layer of peptidoglycan structures typically made of
alternating modified glucose NAG or NAM
amino acids like L-ala D-ala D-Glu L-lys or DAP
how can the peptidoglycan structure be destroyed
by lysozymes, which cleave the glycosidic bond between sugars and is found in human secretions, defense against bacterial infection
whats the difference between peptidoglycan arrangement in gram + and gram -
gram + = have a bridge of pentaglysines that cross link the two peptidoglycan
gram - = have a direct cross link between 2 peptidoglycan
what is unique about bacteria structure
peptidoglycan
can be used as a target for antibiotics (the enzymes responsible for its biosynthesis) like in penicillin or vancomyacin
how do peptidoglycan structures grow
synthesis complex that extends the chains of amino sugars
penicillin binding proteins catalyze the formation of peptide cross bridges
extension as a whole is organized by protein complex that includes MreB which is an actin homologue
what are 3 different places that bacterial species can synthesize new peptidoglycans
in dispersed zones
at the septum (middle)
at the poles
whats the difference in the cell envelope between gram + and gram -
gram + = very thick peptidoglycan layer, will stain blue with gram stain
gram - = has thin peptidoglycan layer, will stain pink with gram stain. has LPS which needs to be cleared if used by humans
describe in detail the structure of gram + bacterial cell wall
has multiple layers of peptidoglycan threaded by teichioc acids
techoic acid is negatively charged, a glycopolymer that helps with ridigity and protects against high temperatures and high salt conditions, and antiobiotics
only small things go through the cell wall so the bacteria has to secrete enzymes to break down bigger molecules
lipoteichoic acid are teichoic acids covalently bound to membrane lipids
describe in detail the structure of gram negative bacteria cell wall
LPS consists of core polysaccacharide -> O polysaccacharide and lipid A
different sugars form the LPS and the lipid A part is the thing that anchors sugars to outer membrane
it also is the thing that makes the immune system react, as it sees it as toxic
outer membrane -> LPS stuff attached
peptidoglycan layer middle
inner membrane
braun lipoprotein is a transmembrane protein spanning the outer membrane to peptidoglycan layer
