L7 - Diversity & Biology Of Bacteria 1 Flashcards
What is the bacteria binomial nomenature?
Genus + species
What are the prominent bacterial diseases that cause the most harm?
- Black Death (yersinia pestis)
- cholera (vibrio cholerae)
- tuberculosis (mycobacterium tuberculosis)
- bacterial meningitis (high fatality rate)
What are some common foodborne bacterial infections?
Salmonella
Clostridium
Campylobacter
Staph aureus
Listeria
Escherichia
What is the importance of the Microbiome
- development of the intestinal immune system
- homeostasis
- prevents colonisation by bacterial pathogens
- effects on extra-intestinal autoimmune diseases
Bacterial structure: nucleoid
DsDNA, circular chromosome, spatial organisation (supercoiled)
Bacterial structure: ribosomes
70s ribosome (30s and 50s subunit)
- coupled transcription/translation
Why are ribosomes the major target for antibacterial drugs
So bacterias can’t make proteins
Why do we use 16s rRNA to study Microbiome
It has a low mutation rate and is highly conserved so it is useful to study phylogenetic studies
- by using primers on the most conserved sequence, we can sequence by PCR and amplify to see what bacteria is there
Bacterial structure: cytoplasmic cell membrane
Lipid Bilayer structure similar to eukaryotic membranes but no steroids
- anchor for proteins
- osmotic barrier
- transport of solutes
- synthesis of lipids
Describe structure of cell wall
Rigid layer around membrane
- peptidoglyan = polysaccharide chains with peptide cross links containing other molecules
- resists osmotic pressure and determines cell shape
- signal to innate immune system of bacterial presence
Describe gram stain procedure and results
Procedure:
- fixation
- crystal violet
- iodine treatment
- decolourisatoin
- counter stain safranin
Gram positive = purple negative = pink
Describe the cell wall composition of gram negative and gram positive
Negative
- 2 thin layers of peptidoglycan with periplasm space
Positive
- thick layers of peptidoglycan
Describe what it means by an ‘acid-fast’ cell envelope
- large amounts of wax (mycolic acid, long branched complex fatty acids)
- hydrophobic layer -> impenetrable to many harsh chemicals, disinfectants and strong acids
- reduced rate of nutrient uptake
What is the role of peptidoglyan cell wall
- mechanical strength
- counteract osmotic pressure of cytoplasm
- role in bacterial replication
- target for some antibiotic
What are the glucose derivatives of peptidoglycan cell wall and how is it cross linked to one another
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)
Linked by tetrapeptide
How does the bacteria cell wall trigger inflammatory responses in immune cells?
Recognition via NOD1 and NOD2 receptors
- activation of NF
- production of pro-inflammatory cytokines
What enzyme targets peptidoglycan as a critical host defence strategy
Lysozyme detects these fragments in the absence of obvious infection
How do bactera evolve to evade this mechanism to enhance pathogenicity
Modify their cell wall:
- tuberculosos - animation of glutamic acid residues NOD1 ending
- pneumoniae and listeria - N-deacetylation of sugars to reduce inflammation activation NOD2 signalling
What is the significance of teichoic acids in gram positive bacteria
- chains of glycerol phosphate/ribitol phosphate bound covalently to peptidoglycan
- provides rigidity
- role in cell morphology and division
- major surface antigen
- promote interactions with host cells and biofilm formation
- promote adherence to cells
- pro inflammatory responses through toll like receptors 2
What is the composition of inner and outer leaflet of gam negative cel wall
Inner = phospholipids
Outer = LPS
Periplasmic space of gram negative bacteria is referred to as multipurpose compartment. Why?
- contains transport systems for iron, proteins, sugars and other metabolites
- hydrolytic enzymes
- virulence factors (collagenases, hyluronidases proteaases b lactamases)
What is LPS? What are the 3 types? What is its importance?
It is an endotoxin that causes fever
Lipid A, core polysaccharide, o-polysaccharide
- essential for bacterial viability
- hydrophilic O-polysaccharide repels hhydrophobic molecules that would otherwise penetrate
- small hydrophilic enters through porins
How is LPS used to classify bacteria
O antigen = O157
