CH 3d inner structures Flashcards
CH 3d
Cytoplasm
Bounded by the plasma membrane Highly organized (even without organelles) - cytoskeleton and many functional membrane extensions
CH 3d
Cytoskeleton
Structural elements of the cell:
- microfilaments, actin
- intermediate filaments
- microtubules, tubulin Maintaining cell shape
Cell division
Organization/ protein localization within the cell
CH 3d
FtsZ
Part of cytoskeleton that forms a ring where the cell will divide and eventually constricts and pinches the bacteria into two new cells.
CH 3d
Internal membranes
Most, but not all bacteria, have extensive functional inner membranes that are associated with the plasma membrane (not separate organelles) - may be involved in respiration, photosynthesis, etc.
CH 3d
Inclusion Bodies
Storage: - nutrients - waste Reduce osmotic pressure - make proteins insoluble (not drawing water into the cell) Metabolic functions Motility
CH 3d
Structure of Inclusion Bodies
Some are free, others bound by a protein shell or lipid layer.
Surrounded by extension of plasma membrane.
CH 3d
Inclusion Bodies and storage
Carbon (PBH)
Nitrogen (cyanophycin granules in cyanobacteria)
Phosphate (Corynebacterium diphtheriae - club shape comes from inclusion bodies)
Sulfur (waste - prevents sulfur from becoming toxic in the cell - gives Thiomargarita its sheen)
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Inclusion Bodies and metabolic functions
Special type: carboxysome - location of the Calvin cycle, building sugar molecules (RuBisCo)
CH 3d
Inclusion Bodies and motility
Different kinds; two examples are gas vacuoles and magnetosomes
CH 3d
Gas vacuoles (inclusion bodies and motility)
Regulate gas in the gas vesicles, changing the buoyancy of the bacteria, allowing them to change level in water (closer to surface or bottom)
CH 3d
Magnetosomes (inclusion bodies and motility)
Small bodies composed of magnitite particles - can orient themselves up/down or N/S/E/W.
Often have 15 or so magnitite particles in a row to make up the magnetosome.
CH 3d
Ribosomes
Function: protein synthesis
- very similar to eukaryotic ribosomes - many believe that ribosomes were originally a unique organism that came to live in coexistence with prokaryotic cells and then stayed in the cells as eukaryotes evolved. Structure: slightly smaller than eukaryotes; about 70S with the two units combined
- large subunit (50S)
- small subunit (30S)
CH 3d
Nucleiod
Generally a large, single, circular DNA molecule, not separated from the cytoplasm by a membrane.
Very organized - Nuclear Associated Proteins (supercoiling)
Example: E. coli = 4Mb = 1.4 mm
CH 3d
Plasmids
Extrachromosomal DNA - not required for bacteria to grow and reproduce normally, but it has genes that are advantageous under certain environmental conditions. When resources are scare, the plasmid won’t continue to replicate. small, double-stranded DNA that can exist independently of chromosome
Replicate autonomously.
Episomes:
- plasmids that insert into the chromosome
- replicate with the chromosome
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Episomes
Plasmids that insert into the chromosome.
Replicate with the chromosome.
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Common types of plasmids
Conjugation
- F plasmid (sex pilus)
- R plasmid (antibiotic resistance)
Bacteriocin-encoding
- inhibit growth of other bacteria; prevents competition for resources
Virulence
- encode factors involved in pathogenecity (capsule/ toxic proteins)
Metabolic
- enable bacteria to use a variety of food sources
CH 3d
Pili
Short, hair-like appendages from cell surface
Involved in conjugation - can transfer DNA across species
sex pili involved in conjugation
CH 3d
Fimbriae
Short, hair-like appendages from cell surface
Involved in attachment and motility
CH 3d
Flagellum
pl. flagella
Described based on location. Same structure in all bacteria: Filament Hook Basal body
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Types of flagella
Monotrichous: 1 flagellum
Amphitrichous: multiple flagella on one end of bacteria
Lophotricous: multiple flagella that come from same point
Peritrichous: flagella all over the cell
CH 3d
Flagellum structure
Filament
- end that extends past cell wall/ outer membrane
- simple protein flagellin subunits arrange themselves in hollow tube
Hook
- gives bent flagellum a propeller-like movement
- covered in the sheath
Basal Body
- fairly complex motor region; rod parts spin
- movement driven by H+ gradient
CH 3d
Bacterial motility
Swimming with flagella
Corkscrew movements of spirochetes
Fimriae
Gliding
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Taxis
Directed motility - "random motion with a purpose" - moves towards or away from certain stimulants; receptors detect presence of attractants or repellants Types: chemotaxis = nutrients/ repellants thermotaxis = temp phototaxis = light aerotaxis = oxygen osmotaxis = osmotic pressure
CH 3d
Flagella movement with taxis
- Run: counterclockwise rotation, one spot to another
- Tumble: clockwise rotation, orient cell Without a signal, they move randomly.
If a bacteria detects a foodsource, they’ll run in that direction for a while before having to stop and tumble. Then they’ll start running again; if it’s in the direction of food, they’ll go a while before tumbling. If it’s not, then they’ll stop running, tumble, and hope that next time they run they’re going toward food.
CH 3d
Swarming
Groups of cells moving together. Herd mentality of the colony working as a community.
Example: Myxococcus xanthus
CH 3d
Axial Fibril
Internal flagellum in spirochetes - work in the periplasmic space between cell wall and outer membrane.
Causes corkscrew movement.
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Twitching and gliding
Involve fimbriae and/ or slime layer.
Twitching:
- fimriae alternately extend and retract to move bacteria
- intermittent, jerky Gliding:
- may involved fimbriae, always has slime layer
- smooth
CH 3d
Endospores
Protective structure that is formed around DNA and most important proteins when conditions are bad - resistant to most things and allows bacteria to be dormant for extended periods of time.
Very thick structures - don’t take up stains/ impervious to chemicals
Generally G+ and soil species
- Clostridium
- Bacillus
- Sporosarcina
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Functions of endospores
Resistance to…
- UV
- desiccation
- heat
- chemical disinfectants
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Endospore structure
Core (DNA and proteins) Core wall Cortex Inner Coat Outer Coat
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Endospore locations within the cell
Central
Subterminal
Terminal
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sporulation
making endospores, complex process in organized fashion over several hours
CH 3d
Endospore return to vegetative state
(Becoming an actively growing cell again)
Complicated process needing exact environmental conditions
- Activation
- Germination
- Outgrowth
