Bacteria Flashcards
What are the 4 phyla of bacteria ?
- proteobacteria
- actinobacteria
- firmicutes
- bacteriodetes
Describe prokaryotic DNA
- Typically a single circular chromosome that aggregates to form the nucleoid region
- may also have plasmids
- small & compact
Describe plasmids
circular/linear double-stranded DNA that replicate separately from chromosome
What are the 3 major cell morphologies ?
- coccus
- bacillus
- spirillum
What shape does coccus describe ?
spherical
What shape does bacillus describe ?
rod/cylindrical
What shape does spirillum describe ?
spiral
What are some unusual bacteria shapes?
- spirochetes
- appendages bacteria
- filamentous bacteria
Describe the peptidoglycan cell wall
- rigid layer that provides strength to the cell wall
- polysaccharide
- can be gram-positive or negative –> effects cross-linkage
What is the peptidoglycan cell wall comprised of ?
- amino acids
- lysine/diaminopimelic acid
- N-acetlyglucosamine
- N-acetylmuramic acid
Describe the structure of a gram-positive peptidoglycan cell wall
- upto 90% peptidoglycan
- common to have teichoic acids covalently bound peptidogylcan
- lioteichoic acids
- divalent metal ions are bound prior to transport
What are lipoteichoic acids ?
teichoic acids covalently bound to membrane lipids
Describe the LPS - Outer membrane of prokaryotes
- lipopolysaccharide layer makes up most of the cell wall
- barrier against antibiotics & harmful agents
- LPS replaces most of the phospholipids in the outer half of the outer membrane
What does the LPS/lipopolysaccharide consist of ?
- core polysaccharide
- O-polysacchairde
- lipid A
What is endotoxin ?
Lipid A –> the toxic part of the LPS
What are differential stains?
different kinds of cells are different colours
What are a good example of differential staining ?
- Gram stains
- positive = purple/violet
- negative = pink
Describe the structure of capsules & slime layers
- polysaccharide layers
- assists in the attachment to surfaces
- protects against phagocytosis
- resists desiccation
Describe fimbriae
- filamentous protein structures - 2-10nm wide
- enables organisms to stick to surfaces or form pellicles
What are pellicles ?
thin sheets of cells on a liquid surface
Describe Pili
- typically longer and fewer per cell than fimbriae
- conjugative/sex pili facilitate genetic exchange between cells
- Type IV pili adhere to host tissues & support twitching motility
Describe Endospores
- highly differentiated cells resistant to hear, harsh chemicals and radiation
- ‘dormant’ stage of bacterial life cycle
- ideal for dispersal via wind, water or animal gut
When are endospores formed ?
during endosporulation or sporulation
Where are endospores present ?
- only in some gram-positive bacteria
Describe the formation of endospores
- vegetative cell converted to non-growing, heat-resistant, light refractive structure
- only occurs when growth ceases due to lack of essential nutrients such as nitrogen or carbon
Describe the function of flagella
- structure that assists in swimming in bacteria
Describe Flagella & Flagellation
- long, thin appendages - 15-20nm wide
- helical in shape with a filament made of flagellin
- increase/decrease rotational speed relative to strength of proton motive force
What are the different arrangements of flagella ?
- polar
- lophotrichous
- amphitrichous
- peritrichous
