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98 Cards in this Set
- Front
- Back
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How are Prokaryotes Different from Eukaryotes?
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The way their DNA is packaged
The makeup of their cell wall Their internal structures |
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How are Prokarotes' DNA packaged
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No nucleus
Not wrapped around histones |
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What does the cell wall of a prokaryote such as bacteria consist of?
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peptidoglycan
or in Archae- tough and made of other chemicals, distinct to them |
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what is different about a prokaryotes internal structure
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No complex, membrane-bound organelles
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What are some external features of prokaryotic cells?
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Appendages - i.e. flagella, pili, fimbriae
Glycocalyx - capsule, slime layer |
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what is the cell envelope of a prokaryotic cell
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consists of outer membrane, cell wall, and cell membrane
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what are some internal structures of prokaryotic cells?
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cytoplasm, ribosomes, inclusions, nucleoid/chromosome, actin cytoskeleton, endospores
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what are four structures common to all bacterial cells?
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Cell membrane
Cytoplasm Ribosomes One (or a few) chromosomes |
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what are two structures found in MOST bacterial cells?
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Cell wall
Surface coating or glycocalyx |
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what are 8 structures found in SOME bacterial cells?
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Flagella, Pili, Fimbriae, Capsules, Slime layers, Inclusions, Actin cytoskeleton
Endospores |
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what are most of the one or few chromosomes of a prokaryote shaped like?
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circular
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what is a plasmid?
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double stranded DNA circle containing extra genes
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what are cell extensions such as flagella and axial filaments used for?
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motility
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what are cellextensions such as pili and fimbraie used for?
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mating and attachment
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what are the three parts of a flagella?
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filament, hook (sheath), and basal body
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what is the name for:
single flagellum? small bunches or tufts of flagella emerging from the same site? flagellum dispersed randomly over the structure of the cell? |
monotrichous
lophotrichous peritrichous |
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what is the function of flagellum?
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allows motility toward and away from stimulus by chemotaxis and phototaxis
moves by runs and tumbles |
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in what type of bacteria are pili found?
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gram-negative bacteria
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what are pili made of?
what are they used for? |
Elongate, rigid tubular structures made of the protein pilin
conjugation - the horizontal gene transfer (passing of plasmids) Requires direct cell contact |
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describe fimbriae
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Small, bristlelike fibers
Most contain protein Tend to stick to each other and to surfaces Like velcro |
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what is the function of glycocalyx
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Protects the cell
Sometimes helps the cell adhere to the environment |
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what does the glycocalyx consist of?
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a coating of repeating polysaccharide units, protein, or both
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what are the two forms that glycocalyx can take?
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Slime layer or capsule
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describe a slime layer
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when the glycocalyx fomrs a loose shield that protects some bacteria from loss of water and nutrients
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describe a capsule
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when the glycocalyx is bound more tightly to the cell and is denser and thicker
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the glycocalyx is formed by many ________________ bacteria to protect them against ____________.
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pathogenic
phagocytes |
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what is important in the formation of biofilms?
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the glycocalyx
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what are the differences btw gram + and gram - bacteria?
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Diffs lie in the cell envelop.
Gram-positive: Two layers Cell wall and cytoplasmic membrane Gram-negative: Three layers Outer membrane, cell wall, and cytoplasmic membrane |
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describe the cell wall
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Helps determine the shape of a bacterium
Provides strong structural support Most are rigid because of peptidoglycan content |
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what is a biofilm?
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mulitple organism types collaborating to protect the group against attack - held together by the glycocalyx
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what is the cell membrane made up of?
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phospholipids
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what is the cell wall made up of?
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peptidoglycan
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the cell wall keeps the cell from ______ due to changes in pressure that result from _________
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rupturing
osmosis (Pressure inside cell is greater than on the outside.) |
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describe the Gram positive cell wall
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A thick (20 to 80 nm), homogeneous sheath of petidoglycan
Contains tightly bound acidic polysaccharides |
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describe the Gram negative cell wall
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Single, thin (1 to 3 nm) sheet of peptidoglycan
Periplasmic space surrounds the peptidoglycan |
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what is distinctive about mycoplasmas?
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lack a cell wall entirely
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is archae gram - or gram +?
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neither - they have unusual and chemically distinct cell walls
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what is the mycolplasma cell membrane stabilized by? Which makes it resistant to?
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sterols
lysis |
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describe mycoplasmas
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Very small bacteria (0.1 to 0.5 µm)
Range in shape from filamentous to coccus Not obligate parasites Can be grown on artificial media Found in many habitats |
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Give an example of an important medical species of mycoplasmas
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Mycoplasma pneumonia
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what protects mycobacteriums and nocardia from dessication and dehydration if they don't have a cell wall?
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unique types of lipids and in the mycobacteria, mycolic acid that surrounds it.
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archae have a cell wall consisting of
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polysacharrides and glycoproteins instead of peptidoglycans
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Describe L-Forms
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a phase of bacteria that are very small and lack cell walls.
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The Gram Negative outer membrane contains what?
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specialized polysaccharides and proteins
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The uppermost layer of the Gram negative outer membrane contains what?
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lipopolysaccharide
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The innermost layer of the Gram negative outer membrane contains what?
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phospholipid layer anchored by lipoproteins to the peptidoglycan layer below
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Describe the outer membrane of a Gram negative cell.
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serves as a partial chemical sieve
Only relatively small molecules can penetrate |
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Access through the Gram - outer membrane is provided by special ____________ formed by _____________.
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membrane channels
porin proteins |
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what is another name for the cell membrane?
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cytoplasmic membrane
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the cell membrane contains primariily __________ and ________
Exceptions: |
phospolipids and proteins
mycoplasmas and archae |
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what are the functions of the cell membrane?
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mycoplasmas and archae
Functions Provides a site for functions such as energy reactions, nutrient processing, and synthesis Regulates transport (selectively permeable membrane) Secretion |
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which is more difficult to kill, Gram - or Gram + bacteria?
Why? |
Gram -
B/c the outer membrane provides an extra barrier, making them impervious to some antimicrobial chemicals. |
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Describe the contents of the cell cytoplasm in prokaryotes
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Gelatinous solution
Site for many biochemical and synthetic activities 70%-80% water Also contains larger, discrete cell masses (chromatin body, ribosomes, granules, and actin strands) |
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Describe the prokaryotic bacterial chromosome
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Single circular strand of DNA
Aggregated in a dense area of the cell- the nucleoid |
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what are plasmids?
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Nonessential pieces of DNA
Double-stranded circles of DNA |
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what is the function of plasmids?
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To confer DNA. Often includes protective traits such as drug resistance or the production of toxins and enzymes
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Plasmids are frequently employed in __________
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Biotech applications
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what are ribosomes made up of?
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RNA and protein
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what is rRNA
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ribosomal RNA - a special type of RNA
function of the rRNA is to provide a mechanism for decoding mRNA into amino acids |
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what is rRNA characterized by?
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S units
the prokaryotic ribosome is 70S, consisting of a large 50S subunit and a small 30S subunit |
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describe inclusions in prokarytic cells
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Serve as a storehouse when nutrients become depleted
Some bacteria lay down nutrients in these inclusions during periods of nutrient abundance Some aquatic bacterial inclusions include gas vesicles to provide buoyancy and flotation |
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what are granules?
What do they contain? |
A type of inclusion body which Are not enclosed by membranes
contain crystals of inorganic compounds |
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give some examples of granules
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sulfur granules of photosynthetic bacteria
Polyphosphate granules of Corynebacterium and Mycobacterium are called metachromatic granules because they stain a contrasting color in methylene blue Magnetotactic bacteria contain granules with iron oxide- give magnetic properties to the cell |
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describe the actin cytoskeleton
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Long polymers of actin
Arranged in helical ribbons around the cell just under the cell membrane ***Contribute to cell shape |
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what are bacterial endospores?
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an extremely resistant stage, dormant bodies - when the org gets stressed, it packages its genetic material and ribosomes into a spore - hardest thing to kill - can last thousands of years
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Give an example of an endospore-producing bacterium
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Bacillus and Clostridium and Sporosarcina
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what are the two stages of endospore-forming bacteria life cycle?
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Phase one - Vegetative Cell
Phase Two - Endospore |
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Describe the vegetative phase
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Metabolically active and growing
Can be induced by the environment to undergo spore formation (sporulation) |
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describe the endospore phase
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Stimulus for sporulation- the depletion of nutrients
Vegetative cell undergoes a conversion to a sporangium Sporangium transforms in to an endospore |
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describe an endospore
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Withstand extremes in heat, drying, freezing, radiation, and chemicals
Heat resistance- high content of calcium and dipicolinic acid Some viable endospores have been found that were more than 250 million years old |
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describe germination of the endospore
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Breaking of dormancy
In the presence of water and a specific germination agent Quite rapid (1 ½ hours) The agent stimulates the formation of hydrolytic enzymes, digest the cortex and expose the core to water |
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Give some medically significant examples of endo-spore-forming bacterial pathogens.
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Bacillus anthracis
Clostridium tetani Clostridium perfingens Clostridium botulinum |
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What are the three general shapes of bacteria
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coccus
Bacillus Spirillum |
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What shape does coccus describe?
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roughly sperical
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what shape does "bacillus" describe?
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rod-shaped
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what are two variations of the bacillus shape
describe |
Coccobacillus- short and plump
Vibrio- gently curved |
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what shape does "spirillum" describe?
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curviform or spiral-shaped
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define pleomorphism
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when cells of a single species vary to some extent in shape and size
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what are the different ways cocci can be arranged?
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Single
Pairs Tetrads Irregular clusters Chains Cubical packet |
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what is the name for pairs of cocci?
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diplococcic
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what is the name for irregular clusters of cocci?
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staphylococci and micrococci
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what is the name for chains of cocci?
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streptococci
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what is the name for a cubical packet of cocci?
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sarcina
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what is the name for pairs of bacilli?
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diplobacilli
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what is the name for a chains of bacilli?
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streptobacilli
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what is the name for rows of bacilli cells oriented side by side?
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palisades
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what arrangements do spirilla take
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singular or occasionally found in short chains
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what is used to classify prokaryotes?
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their shape, variations in arrangement, growth characteristics, and habitat
and more recently, rRNA sequence |
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what is the Definitive published source for bacterial classification
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Bergey's Manual (1st published in 1923)
Early classification- the phenotypic traits of bacteria Current version- combines phenotypic information with rRNA sequencing |
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what are the 4 taxonomic divisions of the Kingdom Prokaryotae based on? What are they?
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based upon the nature of the cell wall
Gracilicutes- gram-negative Firmicutes- gram-positive Tenericutes- lack cell wall Mendosicultes- the archae |
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Many medical microbiologists prefer __________ for classifying bacteria
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diagnostic scheme
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why does the Common definition of species used for animals (can produce viable offspring only when it mates with others of its own kind) not work for bacteria
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Because Bacteria do not exhibit a typical mode of sexual reproduction
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how are bacterial species defined
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For bacteria- a species is a collection of bacterial cells, all of which share an overall similar pattern of traits
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describe subspecies of bacteria
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Subspecies, strain, or type- bacteria of the same species that have differing characteristics
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what does the serotype of a bacteria describe?
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Serotype- representatives of a species that stimulate a distinct pattern of antibody responses in their hosts
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describe rickettsias
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very tiny obligate intracellular parasitic, gram-negative bacteria
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Rickettsias survive how?
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Most-pathogens that alternate between a mammalian host and blood-sucking arthorpods
Cannot survive or multiply outside a host cell Cannot carry out metabolism completely on their own |
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what are some diseases caused by rikettsias
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Rocky Mountain Spotted Fever by Rickettsia rickettsii
Endemic typhus by Rickettsia typhi |
