bacteria Flashcards
(23 cards)
monotrichous
single polar flagellum
lophotrichous
multiple flagella at polar end
amphitrichous
two flagella, one at each end
peritrichous
flagella all over the surface
atrichous
bacteria without flagella
bacteria with outer membrane
gram-negative; have a thinner peptidoglycan layer
bacteria without outer membrane
gram-positive; have a thicker peptidoglycan layer
phospholipid molecule
- one of the molecules which make up the cell membrane
- hydrophilic head and two hydrophobic tails
- heads align together in water to create a stable but dynamic structure that excludes water
capsule function
aids in evading the immune system of a target; hides the bacterial cell surface from detection
ribosomes
- protein synthesis
- 70S ribosomes in bacteria → svedburg units for how fast a particle settles out of a solution
- bacterial ribosomes are targeted when creating antibiotics as they are different from eukaryotic ribosomes (80S) → for disrupting protein synthesis
storage granules
glycogen or polyphosphate
vesicles
gas or lipid
endospore
resistant resting structure in certain species → produces resting structure of one spore when nutrients start to run out, which in turn produces one bacterium at a later date
pili
- small projections used to attach the host to surfaces
- conjugative pili are involved in genetic material transfer in conjugation
bacterial growth curve
- lag phase
- acceleration
- exponential phase
- decline
- stationary phase
- death phase
factors affecting bacterial growth
- physical factors → e.e. pH, temp, oxygen concentration + moisture
- nutritional factors → carbon, nitrogen, vitamins (in some cases)
lag phase
- adaptation → new environment for cells
- no significant increase in number
- metabolically active cells
- growth in size
- synthesise enzymes
- produce energy (ATP)
exponential phase
- cells have adapted
- growth occurs at exponential rate
- division happens at maximum rate
- generational time → genetically determined time for how long it takes to divide + copy
stationary phase
- cell division rate decreases
- nutrient limitation
- build up of toxic waste products produced that are not removed when in media
death phase
- cells lose ability to divide
- cells die
- total count may remain high as cell wall is still visible
- viable count decreases
- some organisms avoid this by producing spores, or becoming dormant structures
complex media (for prokaryote growth)
flexible, cheap → variable source of nutrients e.e. yeast or meat extract for amino acids
synthetic medium
- requires more knowledge of nutrient requirements of the organism
- more expensive
- well-defined composition
natural medium
sample or extract of natural → e.e. milk, pond water
