L4 Bacteria, structure, function & taxonomy Flashcards
what do unicellular microorganisms rely on
hosts
where do unicellular microorganisms live
free living
what is monera
single cell
what is protists
single cell
what is grouped in monera
prokaryotes
what are prokaryotes
eubacteria
archaeobacteria
what is grouped in protists
eukaryotes
what are eukaryotes
protozoa
algae/slime moulds
what is the structure of a typical bacterial cell
pili flagellum outer membrane cell wall inner membrane ribosomes genome of DNA folded and organised no nucleus/nuclear membrane
how does the bacteria move
flagellum for motility anchored in cytoplasmic membrane – needs energy from cytoplasmic membrane (electron transport chain)
where is the peptidoglycan
cell wall
do prokaryotes or eukaryote protist have nucleic acids
both do
do prokaryotes or eukaryote protist have structured nucleus
prokaryotes -
eukaryotes +
do prokaryotes or eukaryote protist have mitochondria
prokaryotes -
eukaryotes +
do prokaryotes or eukaryote protist have ribosomes
both do
do prokaryotes or eukaryote protist have cell membrane
both do
do prokaryotes or eukaryote protist have rigid PG cell wall
prokaryote +
eukaryotes -
do prokaryotes or eukaryote protist have mesosome
prokaryote +
eukaryotes -
do prokaryotes or eukaryote protist have ER/Golgi
prokaryote -
eukaryotes +
what is a mesosome
invagination of cytoplasmic membrane important for cell division to make daughter cells
what is the binomial system for naming bacteria
genus + species
why is bacterial taxonomy important
handling info learning communication identification evolution
what are the phenotypic characteristics
morphology - macro/micro-scopic biotyping - biochemical tests serotyping antibiogram patterns
macroscopic growth characteristics
shape margin elevation size texture appearance pigmentation optical density
what is beta hemolysis
complete hemolysis = yellow no red on blood agar
what is alpha hemolysis
degraded partially, characteristic green/brown colour
microscopic growth characteristics
shape
size
staining
arrangement
what are the shapes of microscopic growth
rod club coccus (round) curved (vibrio) spirillum spirochaete
what are the staining charactersitics
gram stain - true bacteria
acid fast stain - mycobacteria
how are the genotypic characteristics tested
% GC ratios DNA hybridisation chromosomal DNA fragment analysis ribotyping MALDI_TOF
what is MALDI TOF
Matrix-Assisted Laser Desorption/Ionization-Time Of Flight
sample mixed in liquid matrix with solvent (maybe acid) break up any vegetative bacteria, crystallise and hit with a laser = desorbs the material, ionises it and put through a vacuum column and hit detector = mass spectra gram of the sample
what is ribotyping
extract DNA and break up enzymatically into smaller linear units and probs single stranded DNA that has been enzymatically broken up into ribosomal RNA genes that are unique to specific organisms - rRNA-based phylogenetic analyses
what is DNA hybridisation
species specific probes that are specific to specific bacteria = if makes ds then it is the organism that you think it is
what is the difference between gram + and - cell wall
gram + is thick
gram - is thin
how does a gram stain work
crystal Violet stain
gram’s Iodine (mordant, fixes crystal violet)
decoloriser
(alcohol/acetone)
(gram+ve PG too thick so not stripped)
safranin red (counter stain, gram-ve gets stained)
do gram + and gram - have an outer membrane
gram +ve has no outer membrane
gram -ve has got an outer membrane
do gram + and gram - have and LPS (endotoxin)
gram +ve doesnt
gram -ve does
do gram + and gram - have teichoic acid
gram +ve does
gram -ve doesnt
do gram + and gram - sporulate
some strains of gram +ve do
gram -ve dont
do gram + and gram - have a capsule
sometimes
are gram + and gram - lysozyme sensitive
gram +ve are
gram -ve are not
what is lysozyme function
hydrolyses PG
which of the gram + and gram - are more susceptible to penicillin
gram +ve most susceptible
what is teichoic acid interlinked with
PG
what is LPS made up of
lipid A, outer core made of carbohydrate, O antigen
what is the function of cell wall
maintain rigidity, cell shape/structure maintain osmolarity (prevent osmotic lysis) survival - interacts with host membranes cell division - form cross wall separating 2 daughter cells
what is a cell wall made up of
two disaccharide sugars - N-acetylglucosamine and N-acetylmuramic acidalternating
what form are amino acids in - in cell wall
natural form of amino acid is L isomeric form
where are D isomeric forms found
cell wall there is a D isomeric form only form in nature where D isoform is made
how are adjacent stem peptides linked to the cell walls
linked directly by transpeptidase reaction (e.g. in E. coli) whereas in some gram positive have penta-glycine (5 glycine amino acids) form a cross bridge between adjacent stem peptides – where AB work
how do antibiotics with beta lactam structure work
molecular mimic for the stem peptide amino acid, interact with pencillin binding protein or transpeptidase enzyme and prevent that enzyme binding to amino acids ion stem peptide to form cross bridge
no cross bridge = no PG effective structure no cell wall and bacteria die (bactericidal)
how does vancomycin work
binds to terminal D-ala molecular inhibition - also prevents transpeptidation of adjacent stem peptides
how does the bacterial cell wall synthesise
PG precursor synthesised inside cell
exported across cell membrane
site is created in existing wall by enzymic action (PBPs)
new nucleotide minus terminal D-ala is encorporated
cell ‘grows
how are mycobacterium different
modified PG layer
covalently attached to arabinogalactan polymer
mycolic acid waxy coat - lipids
poor gram stain
why cant mycobacterium be gram stained
arabinogalactan polymer
how are mycobacterium stained
acid fast gram stain (Zeihl-Neelsen stain) - carbolfuchsin
how are mycoplasma different
no cell wall
cell membrane has steroids from host membrane
what are cell membranes generally like
lipid bilayer - hydrophobic no steroids (except mycoplasma) ion transport and energy production (mitochondria) mesosomes electron transport
what are spores like
cell survival in adverse conditions
desiccation, heat, starvation
what are capsules for
protect against phagocytosis
what are capsules
gelatinous material,polysaccharide/polypeptide
what are flagella for
cell motility
what are flagella like
1-20; peritrichous or polar
coiled in structure
where are flagella
anchored into bacterial membrane
what is the flagella protein
flagellin
what do flagella do
chemotaxis
how do flagella move
ATP driven motor membrane potential
what are fimbriae like
smaller length and diameter than flagella
how are fimbriae arranged
peritrichous arrangement
are fimbriae or flagella coiled
only flagella are
what is the fimbriae protein
pilin
what is the sex pili
F plasmid
what kind of infection do fimbriae cause
e. coli UTI
N.gonorrhoeae
what is LOS
LPS with no O antigen
what has LOS
neisseria
what happens to LPS in cell
shed LPS into constituent moietys, lipid A = inflammatory response, activates cytokines for e.g. increased temp, create fever, organ failure through lack of blood flow
which bacteria have porins
gram -ve
which bacteria have pili
N.gonnorrhea
what are the surface proteins in gram +ve
afimbrial adhesins protein F (Strep. pyogenes)
what do gram +ve bacteria cause on infection
inflammatory response
cytokines/shock
what affect the growth of bacteria
O2/CO2 temperature water pH light osmolarity (5-12%)
what are the nutritional requirements for bacterial growth
carbon and nitrogen source
inorganic salts
organic compounds
what are inorganic salts bacteria require for growth
Fe/Na/K/P/Ca/Mg
what are auxotrophs
can’t make essential nutrient have to get from environment
what is the medical relevance of cell wall synthesis
antibiotics
what is the medical relevance of capsules
vaccines
what is the medical relevance of cell membranes
antibiotics
vaccines
what is the medical relevance of ribosomes
antibiotics
what are monera and protists
like
unpaired chromosomes
no nucleus
