Cell Structure and Function in Bacteria and Archaea Flashcards
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most common shape
cocci or rods
determined by plane of division
determined by separation or not
arrangement
spheres
cocci (singular: coccus)
pairs of cocci
Diplococcus
chains of cocci
Streptococcus
grape-like clusters of cocci
Staphylococcus
cylindrical shape
rod or bacillus
very short rods
coccobacilli
resemble rods, comma shaped
vibrios
rigid helices
spirilla (spirillum)
flexible helices
spirochetes
network of long, multinucleate filaments
mycelium
organisms that are variable in shape
pleomorphic
What is the smallest size of bacteria?
0.3 µm (Mycoplasma)
What is the average rod size of bacteria?
1.1-1.5x2-6µm (E. coli)
What is the very large size of bacteria?
600x80 µm Epulopiscium fishelsoni
important for nutrient uptake; surface to volume ratio
size-shape relationship
True or False: small size may be protective mechanism from predation
true
What are the bacterial cell organization common features?
cell envelope - 3 layers
cytoplasm
external structures
selectively permeable barrier, mechanical boundary of cell, nutrient and waste transport, location of many metabolic processes (respiration, photosynthesis), detection of environmental cues for chemotaxis
plasma membrane
inclusion that provides buoyancy for floating in aquatic environments
gas vacuole
protein synthesis
ribosomes
storage of carbon, phosphate, and other substances
inclusions
localization of genetic material (DNA)
nucleoid
In typical Gram-negative bacteria, contains hydrolytic enzymes and binding for proteins for nutrient processing and uptake; in typical Gram-positive bacteria, may be smaller or absent
periplasmic space
protection from osmotic stress, helps maintain cell shape
cell wall
resistance to phagocytosis, adherence to surfaces
capsules and slime layers
attachment to surfaces, bacterial conjugation and transformation, twitching and gliding motility
fimbriae and pili
swimming and swimming motility
flagella
survival under harsh environmental conditions
endospore
What are the 3 layers of bacterial cell envelope?
plasma membrane
cell wall
layers outside the cell wall
thin barrier that surrounds the cell and separates the cytoplasm from the cell’s environment
bacterial plasma membrane
‘gatekeeper’ for substances that enter and exit the cell
bacterial plasma membrane
True or False: bacterial plasma membrane absolute requirement for all living organisms
true
contains both polar ends and non polar tails
amphipathic lipids
interact with water
hydrophilic
insoluble in water
hydrophobic
loosely connected to membrane; easily removed
peripheral membrane protein
amphipathic-embedded within membrane; carry out important functions; may exist as microdomains
integral
gives structural integrity
hopanoid
comparison of hopanoid in mycoplasma
sterol
rigid structure that lies just outside the cell plasma membrane
peptidoglycan
What are the two types of peptidoglycan based on Gram stain?
Gram-positive and Gram-negative
stain purple; thick peptidoglycan
gram-positive
stain pink or red; thin peptidoglycan and outer membrane
gram-negative
What are the cell wall functions?
confers shape and rigidity on the cell
helps protect cell from osmotic lysis
helps protect from toxic materials
may contribute to pathogenicity
polysaccharide composed of two sugar derivatives (N-acetylglucosamine and N-acetylmuramic acid) and a few amino acids
peptidoglycan
What are the two sugar derivatives of peptidoglycan?
N-acetylglucosamine
N-acetylmuramic acid
Meshlike polymer of
identical subunits
forming long strands (alternating D- and L- amino acids)
peptidoglycan
What is the shape of peptidoglycan strands?
helical
shape
Peptidoglycan chains are crosslinked by ______ for strength
peptides
Composed primarily of
peptidoglycan; May also contain teichoic
acids (negatively charged)
gram-positive cell walls
true or false
some gram-positive bacteria
have layer of proteins on
surface of peptidoglycan
true
true or false
some gram-negative bacteria
have layer of proteins on
surface of peptidoglycan
false
gram-positive
Usually composed of
polysaccharides
Well organized and not
easily removed from cell
Visible in light microscope
capsules
protective advantages of capsules
- resistant to phagocytosis
- protect from desiccation
- exclude viruses and detergents
similar to capsules except diffuse,
unorganized and easily removed
slime layers
slime may aid in
motility
Regularly structured
layers of protein or
glycoprotein that self-assemble
s layers
the S layer
adheres to outer
membrane
gram-negative bacteria
it is associated
with the peptidoglycan
surface
gram-positive bacteria
What are the S-layer functions?
Protect from ion and pH fluctuations, osmotic
stress, enzymes, and predation
Maintains shape and rigidity
Promotes adhesion to surfaces
Protects from host defenses
Potential use in nanotechnology
what are the bacterial cytoplasmic structures?
- Cytoskeleton
- Intracytoplasmic membranes
- Inclusions
- Ribosomes
- Nucleoid and plasmids
plasma membrane and
everything within
protoplast
material bounded by the plasmid
membrane
cytoplasm
What are the 3 eukaryotic cytoskeletal elements in bacteria?
Tubulin homologues
Actin homologues
Intermediate Filaments Homologues
(Unique Bacterial Cytoskeletal Proteins)
What are the different tubulin homologues?
FtsZ
BtubA/BtubB
TubZ
What are the different Actin Homologues?
MamK
MreB/Mbl
ParM
What are the different types of Intermediate Filament Homologues?
CreS (crescentin)
What are the different types of unique bacterial cytoskeletal proteins?
MinD
ParA
functions in cell division and is widely observed in bacteria and archaea
FtsZ
observed only in Prosthecobacter spp.; thought to be encoded by eukaryotic tubulin gens obtained by horizontal gene transfer
BtubA/BtubB
possibly functions in plasmid segregation; encoded by large plasmids observed in members of the genus Bacillus
TubZ
functions in positioning magnetosomes, observed in magnetotactic species
MamK
helps determine cell shape, may be involved in chromosome segregating, localizes proteins; most rod shaped bacteria
mreB;Mbl
functions in plasmid segregation; plasmid encoded
ParM
induces curvature in curved rods; found in caulobacter crescentus
CreS (crescentin)
prevents polymerization of FtsZ at cell poles; found in many rod-shaped bacteria
MinD
segregates chromosomes and plasmids; observed in many species including Vibrio cholerae, C. crescentus, and Thermus thermophilus
ParA
many bacteria; forms ring during septum formation in cell division
FtsZ
many rods; maintains shape by positioning peptidoglycan synthesis machinery
MreB
rare, maintains curve shape
CreS (crescentin)
– observed in many photosynthetic bacteria and many bacteria with high respiratory activity
plasma membrane infoldings
organelle – site of anaerobic ammonia oxidation
Anammoxosome in Planctomycetes
Granules of organic or inorganic material that
are stockpiled by the cell for future use;
inclusions
may be referred to as microcompartments
inclusions
Storage of nutrients, metabolic end products,
energy, building blocks; glycogen storage, carbon storage
storage inclusions
Polyphosphate (Volutin)
phosphate
cyanophycin granules
amino acids
Not bound by
membranes but
compartmentalized for
a specific function
microcompartments
CO2
fixing bacteria
carboxysomes
contain the enzyme
ribulose-1,5,-
bisphosphate
carboxylase (Rubisco),
enzyme used for CO2
fixation
Carboxysomes
found in aquatic, photosynthetic bacteria and
archaea; provide buoyancy in gas vesicles
gas vacuoles
found in aquatic bacteria; magnetite particles for orientation in Earth’s magnetic field; cytoskeletal protein MamK
magnetosomes
sites of protein synthesis
ribosomes
bacterial and archaea ribosome
70s
eukaryotic ribosome
80s
bacterial ribosomal RNA
16S small subunit
23S and 5S in large subunit
Location of chromosome
and associated proteins; Usually 1 closed circular,
double-stranded DNA
molecule
nucleoid
found in bacteria, archaea, some fungi; usually small, closed circular DNA molecules
Extrachromosomal DNA
plasmids that may integrate into chromosome
episomes
Extend beyond the cell envelope in bacteria
external structures
Function in protection, attachment to
surfaces, horizontal gene transfer, cell
movement
external structures such as:
pili and fimbriae
flagella
short, thin, hairlike,
proteinaceous appendages (up to
1,000/cell)
fimbriae; pili
can mediate attachment to
surfaces, motility, DNA uptake
Fimbriae (s., fimbria); pili (s.,
pilus)
longer, thicker, and less
numerous (1-10/cell); genes for formation found on
plasmids; required for conjugation
sex pili
Threadlike, locomotor appendages extending
outward from plasma membrane and cell wall
flagella
functions of flagella
motility and swarming behavior
attachment to surfaces
may be virulence factors
Thin, rigid protein structures that cannot be
observed with bright-field microscope unless
specially stained; Ultrastructure composed of three parts
bacterial flagella
what are the different patterns of flagella distribution?
Monotrichous
Polar flagellum
Amphitrichous
Lophotrichous
Peritrichous
one flagellum
monotrichous
flagellum at end of cell
polar flagellum
one flagellum at each end of cell
Amphitrichous
cluster of flagella at one or both ends
lophotrichous
What are the three parts of flagella?
filament
hook
basal body
extends from cell surface to the tip; hollow, rigid cylinder of flagellin protein
filament
links filament to basal body
hook
series of rings that drive flagellar motor
basal body
complex process involving many genes/gene
products where new flagellin molecules transported through the hollow filament using Type III-like secretion system; filament subunits self-assemble with help of filament cap at tip, not base
flagellar synthesis
What are the different motility?
flagellar movement
spirochete motility
twitching motility
gliding motility
move toward chemical attractants such as
nutrients, away from harmful substances
chemotaxis
Move in response to temperature, light,
oxygen, osmotic pressure, and gravity
motility
Flagellum rotates like a
propeller
how many revolutions per sec is bacterial flagellar movement?
1100 rev/sec
causes forward motion (run)
counterclockwise
disrupts run causing cell to stop and tumble
clockwise rotation
2 part motor
producing torque
flagellum
2 parts producing torque of flagellum
rotor and stator
C (FliG protein) ring and MS ring
turn and interact with stator
rotor
Mot A and Mot B proteins that form channel through plasma
membrane
stator
protons move through Mot A and
Mot B channels using
energy of proton motive force
powers rotation of the
basal body and filament
torque
Multiple flagella form axial fibril which winds around
the cell; Flagella remain in periplasmic space inside outer
sheath
spirochete motility
exhibits flexing and spinning
movements
corkscrew shape
May involve Type IV pili and slime
twitching and gliding motility
pili at ends of cell; short, intermittent, jerky motions; cells are in contact with each other and
surface
twitching
smooth movements
gliding
Movement toward a chemical attractant or
away from a chemical repellent
chemotaxis
Changing concentrations of chemical
attractants and chemical repellents bind
chemoreceptors of chemosensing system
chemotaxis
True or False
In presence of attractant tumbling frequency is
intermittently reduced and runs in direction of
attractant are longer
true
true or false
In presence of attractant tumbling frequency is
intermittently increased and runs in direction of
attractant are longer
false
tumbling freq is reduced
true or false
In presence of attractant tumbling frequency is
intermittently reduced and runs in direction of
attractant are shorter
false
Complex, dormant structure formed by some
bacteria
bacterial endospore
bacterial endospore is resistant to numerous environmental conditions such as:
heat
radiation
chemicals
dessication
what makes an endospore so resistant?
calcium
small, acid soluble, DNA-binding proteins (SASPs)
Dehydrated core
Spore coat and exosporium protect
- Process of endospore formation
sporulation
how many hours does sporulation occurs?
up to 10 hours
Normally commences when growth ceases
because of lack of nutrients; Complex multistage process
sporulation
What are the different parts of Formation of Vegetative cell?
Activation
Germination
Outgrowth
prepares spores for germination; often results from treatments like
heating
activation
environmental nutrients are
detected; spore swelling and rupture of
absorption of spore coat; increased metabolic activity
germination
emergence of
vegetative cell
outgrowth
more permeable than plasma membrane due to presence of porin proteins and transporter proteins
gram negative
form channels to let small molecules
(600–700 daltons) pass
porin proteins
solute concentration outside the cell is less
than inside the cell
hypotonic environments
water moves into cell and cell swells; cell wall protects from lysis
hypotonic environments
solute concentration outside the cell is greater
than inside
hypertonic environments
– water leaves the cell
– plasmolysis occurs
hypertonic environments
how can cells lyse in hypotonic solution?
lysozyme breaks the bond bet N-acetylglucosamine and N-acetylmuramic acid
pennicillin inhibits peptidoglycan synthesis
cells that lose a cell wall that may survive in isotonic environments
protoplasts
spheroplasts
mycoplasma
does not produce a cell wall; plasma membrane more resistant to osmotic
pressure
mycoplasma
