L28B - Introduction To Microbiology And Bacterial Cells Flashcards
What are the 2 cell types?
- prokaryotes - bacteria, archea
- eukaryotes - fungi, protozoa, helminths, slime moulds, algae
What are facts about prokaryotes? (6)
- 1-5mcm
- haploid
- asexual reproductions
- unicellular
- no true nucleus
- cell wall
What are facts about eukaryotes? (5)
- > 10mcm
- diploid
- sexual reproduction
- unicellular/multicellular
- true nucleus
What are facts about viruses? (2)
- no cellular structure
- genetic material surrounded by protein
What are facts about prions?
- no nucleic acid
- pieces of infectious protein
What are examples of prions? (3)
- bovine
- spongiform
- encephalopathy
What are facts about bacteria? (5)
- unicellular
- huge diversity (size, shape, habitat and metabolilsm)
- majority are harmless/even beneficial
- some cause disease (pathogenic)
- some are pharmaceutical contaminants
What is the bacterial classification? (3)
- morphology - cell shape, size, motility, spore forming
- metabolism - use of energy sources/nutrients
- molecular characteristics - protein, lipid structure, seq of gene encoding 16S RNA
What are the bacterial shapes in cocci? (4)
- coccus
- diplococcus
- chains
- clusters
What are the bacterial shapes in rods?
- single rod
- paired rod
- chains
What are the different bacterial shapes? (3)
- cocci
- rods
- spirals
What is the classification of 70S bacterial ribosome?
- 50S subunit (23S rRNA, 5S rRNA + proteins)
- 30S subunit (16SRNA + proteins)
= 70S bacterial ribosome
What is important about 16S rRNA gene seq? (4)
- all bacteria have ribosomes = essential gene
- 16S gene highly conserved
- hypervariable regions (variation between species)
- organisms identified by their sequence
What are the parts in bacteria cell structure? (6)
- plasma (cytoplasmic) membrane
- cytoplasm
- the nucleoid
- plasmid
- prokaryotic cell wall
- ribosomes
What is the plasma (cytoplasmic) membrane like? (4)
- selective semi-permeable barrier
- mediates nutrient transport
- site of secretion and respiration
- site of environment response regulators
What is the cytoplasm? What does it contain? What does it not contain?
- between plasma membrane and nucleoid
- ribosomes (protein translation, 70S), inclusion bodies (contain important nutrients C, P, N, S)
- no mitochondria, no true nucleus
What is the double stranded DNA (dsDNA) like? (4)
- not enclosed by nuclear membrane
- usually single closed circular chromosome
- DNA supercoiled
- 1 copy of each gene
What are plasmids like? (3)
- extrachromosomal, small circular dsDNA
- replicate independently (multiple copies)
- encode auxiliary functions
What is the prokaryotic cell wall like (3)? What is it composed of?
- protects from the environment
- rigidity, strength
- unique to bacteria
- composed of peptidoglycan cross linked to form mesh
What is the peptidoglycan structure? (4)
- glycan backbone made of chain of sugar residues joined by glycosidic bonds
- every other sugar linked to short peptide
- peptides crosslink to another on adj glycan backbone
= strong mesh like structure formed
What does the mesh like structure of the peptidoglycan structure allow?
Molecules to pass in and out
What 2 types of bonds make it strong and rigid?
- glycosidic bonds
- peptide bonds
What are the 2 division of pathogenic baceria due to difference in PG structure?
- gram positive
- gram negative
What is gram positive bacteria like? (3)
- stain purple
- thick PG layer (20-80nm)< 60-80% cell wal
- X-linked to form thick mesh
What is gram negative bacteria like? (3)
- stain pink
- thin PG layer (1-3nm), 10-20% cell wall
- surrounded by outer membrane
What do gram positive cell walls contain? (4)
- teichoic acids - acidic polysacchs bonded to PG, transport metal cations
- lipoteichoic acids - teichoic acids bonded to membrane lipids, release by killed bacteria during infection = inflammatory response
- plasma membrane
- PG
What do gram negative cell walls contain? (6)
- lipopolysaccharide - stabilises membrane structure
- porins
- outer membrane - impermeable to large molecules
- periplasm - gel-like, contains proteins
- PG
- plasma membrane
What are lipopolysaccharides (endotoxin) like?
- strong immunogenic
- extremely toxic to animal cells
- heat resistant
What are the parts of the lipopolysaccharides?
- lipid A - embedded in outer membrane, toxic = endotoxin
- core polysacch - 10 sugars linked to lipid A
- O-specific polysacch - surface of outer membrane - immunogenic
What are examples of gram positive bacteria? (3)
- staphylococcus // S. aureus
- streptococcus // S. pneumoniae
- clostridioides // C. Difficile
What are examples of gram negative bacteria? (3)
- escherichia coli, E. Coil
- pseudomonas // P. Aeuroginosa
- salmonella // S. enterica
What are pathogenic bacteria not classified by gram stain?
- atypicals
- acid-fast bacilli
- bacteria lacking peptidoglycan
What are acid-fast bacilli like?
- cell wall thick waxy lipidic layer
- // mycobacteria tuberculosis
What are bacteria lacking PG like?
- cause intracellular infections
- // mycoplasma pneumoniae (atypical pneumonia, problems for tissue culture Chlamydia spp)
What are examples of bacterial cell components associated with some bacterial cells? (3)
- (endo)spores
- capsules and slime layers
- pili and fimbriae
What are bacterial endospores?
- highly resistant dormant structures
- form inside bacteria in response to adverse conditions (nutrients/oxygen)
What are the types of bacterial endospores?
- dormant - survive w/o water and nutrients
- non reproductive - single ensospore within bacteria, reactivates in response to more favourable conditions
What is the structure of bacterial endospores?
- tough outer coat - layers of proteins and PG (resistant UV radiation, desiccation, freezing, high temp and most disinfectants)
- dehydrated core - cytoplasm and DNA
What are capsules and slime layers?
- capsule - firm, rigid hard to remove
- slime layer - loose layer which is easier to remove
What are slime layers and what are their functions (3)?
Network of polysachh secreted outside of the PG cell wall
- give protection
- aid attachment
- contribute to virulence (evade body defences)
What are fimbria (p-pili)?
Aid attachement to surfaces
What are F-pili?
Used in bacterial conjugation (transfer of genetic material between cells)
What are P-pili and F-pili like? (2)
- morphologically and chemically similar
- hair like structures composed of protein subunits
