Lecture 2- Bacterial cell structure Flashcards
In regards to shape most bacteria can be termed?
Monomorphic
T/F: Most bacteria are pleomorphic?
False, most bacteria are monomorphic
Define pleomorphic.
Being variable in shape and lacking a single, characteristic form
These are responsible for the characteristics of bacteria size and shape.
Genes
T/F: As bacteria age they can change shape?
True
List the 3 basic shapes of bacteria.
- bacillus
- coccus
- spiral
Name the 3 subtypes of spiral shaped bacteria.
- spirillum
- vibrio
- spirochete
These spiral shaped bacteria can have one or more twists.
Spirillum
These spiral shaped bacteria look like like a curved rod
Vibrio
These spiral shaped bacteria are flexible, helical spirals.
Spirochete
List two shape types that are unusual for prokaryotes.
- Star-shaped bacteria
- rectangular bacteria
Bacteria shape arrangement can fall under 3 categories, what are they?
- Pairs
- Clusters
- Chains
Pairs of cocci or bacilli would be called what, respectively?
Diplococci and diplobacilli
Clusters of cocci would be called what?
Staphylococci
Chains of cocci or bacilli would be called what, respectively?
Streptococci and streptobacilli
Diplococci, streptococci, diplobacilli, and streptobacilli bacteria have how many planes of division?
1
Tetrad bacteria have how many planes of divisions?
2
Sarcinae bacteria have how many planes of divisions?
3
What are branched networks of long mulitnucleate filaments?
Mycelium
Do smaller or larger bacteria cells have a greater surface area to volulme ratio?
Smaller cells have greater surface area to volume ratio
What is the benefit for bacteria being smaller rather than larger?
Being smaller increases surface area. As this ratio increases so does the efficiency of the uptake of nutrients as well as the diffusion of other molecules within cell. In turn, this will lead to a more rapid growth rate.
Does cell shape affect the Surface area to volume ratio?
Yes
Comparing a rod with a coccus of the same volume, which will have a greater nutrient flux across its plasma membrane?
The rod because it will have a greater surface area to volume ratio than the coccus
Name some functions of the bacterial pplasma membrane.
- selectively permeable barrier
- mechanical boundary of the cell
- nutrient and waste transport
- location of many metabolic processes
- respiration
- photosynthesis
- detection of environmental cues for chemotaxis
What is the function of a bacterial gas vacuole?
An inclusion that provides buoyancy for floating in aquatic environments
What is the function of bacterial ribosomes?
Protein synthesis
What are the functions of bacterial inclusions?
Storage of carbon, phosphate, and other substances
What is the function of the bacterial nucleoid?
localization of gentic material (DNA)
What is the function the periplasmic space?
- in typical gram-negative bacteria, contains hydrolytic enzmes and binding protiens for nutrient processing and uptake
- in typical gram-positive bacteria, may be small or absent
What is the function the bacterial cell wall?
- protection from osmotic stress
- helps maintain cell shape
What are the functions of bacterial capsules and slime layers?
- Resistance tophagocytosis
- adherence to surfaces
What are the functions of bacterial fimbriae and pili?
- Attachment to surfaces
- bacterial conjugastion and transformation
- twitching and gliding motility
What are the functions of bacterial flagella?
swimming and swarming motility
What is the function of the bacterial endospore?
survival under harsh conditions
Name the 3 components of the bacterial cell envelope.
- plasma membrane
- cell wall
- layers outside the wall (capsule or slime layer)
This structure is a must have for all living organisms.
plasma membrane
T/F: All bacteria have internal membrane systems?
False, some do
T/F: Bacterial membranes are similar to eukaryotic membranes in that they are lipid bilayers and many of their amphipathic lipids are phospholipids
True
Bacterial membranes usually differ from eukaryotic membranes in lacking sterols (steroid-containing lipids). Instead they contain steroid-like molecules called what?
hopanoids
What are the functions of the hopanoids in the bacterial membranes?
They help to stabilize the membrane
Bacterial membrane lipid composition can vary with environmental changes such as temperature. How does this membrane lipid composition change in respons to temperature changes?
- At lower temperatures, bacteria have more unsaturated FAs in their membrane phospholipids
- At higher temperatures, bacteria have more saturated FAs in their membrane phospholipids
Name two ways that archaeal membranes are different from bacterial and eukaryotic membranes.
- They are composed of lipids that differ chemically from those of bacteria and ukaryotes
- Some have a monolayer structurs intead of a bilayer structure
List 2 defining characteristics of bacterial or eukaryotic membrane lipids.
- contain ester bonds
- have 2 hydrocarbons attached to a glycerol
List 3 defining characteristics of archaeal membrane lipids.
- contain ether bonds
- contain branched molecules
- some are contain tetraethers
List 3 plasma membrnae functions.
- It encompasses the cytoplasm
- acts as a selectively permeable barrier
- interacts with the external environment
- receptors for detection of and response to chemicals in surroundings
- transport systems
- metabolic processes
List some characteristics of the cytoplasm of bacteria and archaea.
- substance in which nucleoid, ribosomes, inclusion bodies, plasmids, and cytoskeletal filaments are suspended
- lacks membrane bound organelles
- composed of mostly water
T/F: Homologs of all 3 eukaryotic cytoskeletal elements have been identifed in bacteria and their functions are similar as they are in eukaryotes
True
FtsZ is a bacterial cytoskeletal protein that is a tubulin homolog of a eukaryotic cytoskeletal protein and it is found in many bacteria. What is it’s function?
forms ring septum formation in cell division
MreB is a bacterial cytoskeletal protein that is an actin homolog of an eukaryotic cytoskeletal protein and it is found in bacilli, but not in cocci. What is it’s function?
Maintians shape by positioning peptidoglycan synthesis machinery
CreS is a rare bacterial cytoskeletal protein that is an intermediate filament homolog of an eukaryotic cytoskeletal protein. What is it’s function?
Maintains curve shape
Plasma membrane infoldings would be observed in bacteria perfoming what types of functions?
- many photosynthetic bacteria
- many bacteria with high repiratory activity
What is an anammoxosome and what is its function in Plantomycetes?
It is an organelle. It is the site of anearobic ammonia oxidation
What are inclusions?
granules of organic or inorganic material that are stockpiled by the cell for future use
What are the functions of storage inclusions?
storage of nutrients, metabolic end products, energy, and building blocks
List some molecules storage inclusions are responsible for.
- glycogen storage
- carbon storage
- poly-B-hydroxybutyrate (PHB)
- Glycogen
- phosphate- polyphosphate granules (volutin)
- amino acids- cyanophycin granules
- sulfur granules
List some characteristics of gas vacuoles.
- they are found in aquatic, photosynthetic bacteria and archaea
- they are aggregates of hollow cylindrical structures called gas vesicles
- they provide buoyancy in gas vesicles
List some characteristics of magnetosomes (inclusions).
- they ar efound in aquatic bacteria
- contain magnetit particles (iron) for orientation in Earth’s magnetic field
- contain the cytoskeletal rotein MamK
- helps to form magnetosome chain
What are microcompartments?
bacterial inclusions not bound by membrane but are compartmentalized for specific functions other than storing substances
What are carboxysomes?
- microcompartments within many cyanobacteria and other CO2- fixing bacteria
- contian the enzyme ribulose-1,5-bisphosphate carboxylase (Rubisco). An enzyme used for CO2 fixation
What are the functions of ribosomes?
Protein synthesis
Bacterial ribosmes are know are called 70s ribosomes and are composed of what two subunits?
- small- 30s
- large 50s
Eukaryotic ribsomes are are also known as _____ ribosomes?
80s
Bacterial ribosomes are made up of primarily ribosomal RNA (rRNA). What types of rRNA makes up the small and large subunits?
- 16s rRNA- small subunit
- 23s rRNA and 5s rRNA- large subunit
If we want to treat a bacterial induced disease in humans what types of ribosomes should we target?
70s
What is the nucleoid?
an irregularly hsaped region that contains the cell’s chromosome and associated proteins
List a few characteristics of the the nucleoid (4).
- It is usually not membrane bound (few exceptions)
- location of chromosome and its associated proteins
- usually 1 closed circular double-stranded DNA molecule
- contains supercoiling and nucleoid proteins (deierent from histones) that aid in folding
List a few characteristics of the prokaryotic chromosome (3).
- usually a circular, double-stranded DNA molecule
- usually only one
- extensively looped and coiled
What are plasmids?
Small, double stranded DNA molecules that exist independently of the chromosome
LIst a few characteristics of plasmids (4).
- extrachromosomal DNA
- found in bacteria, archaea, and some fungi
- usually small, closed circular DNA molecules
- they exist and replicate independently of the chromosome
- episomes- may integrate into chromosome
- inherited during cell division
- contain few genes that are non-essential
- confer selective advandtage to host (e.g., drug resistance)
- classification based on mode of existence, spread, and function
What is the function of conjugative plasmids?
transfer DNA from one cell to another
What is the function of R plasmids?
carry antibiotic-resistance genes
What is the function of Col plasmids?
Produce bacteriocins (substances that destroy closely related species)
What is the function of virulence plasmids?
carry virulence genes
What are the functions of virulence plasmids?
carry genes for enzymes
Does being a gram-negative or gram-positive bacteria allow for extra protection to the cell? Why?
Gram negative because of the presence of the outer membrane
What is peptidoglycan (murein)?
it is a component of the bacterial cell wall; a rigid structure that lies just outside of the plasma membrane
Gram-positive bacteria stain ______ and have _______ peptidoglycan?
purple, thick
Gram-negative bacteria stain _______, have _______ peptidogylcan, and have a(n) ______ ________
pink, thin, outer membrane
List the functions of the cell wall.
- Maintains shape of the bacterium
- almost all bacteria have one
- Helps protect cell from osmotic lysis
- Helps protect from toxic materials
- May contribute to pathogenicity
What is characterisitic of the structure of peptidoglycan?
- it is a meshlike polymer of identical subunits forming long strands
- chains of peptidoglycan subunits are joined by cross-links (covalent bonds) between the peptides
What are the two alternating sugars that make up the peptidoglycan polymer structure?
- N- acetylglucosamine (NAG)
- N- N- acetylmuramic acid (NAM)
T/F: the peptidoglycan structure in addition the two alternating sugars contain alternating D- and L- amino acids?
True
Peptidoglycan strands have a _____ shape?
Helical
Some gram-positive cell wall may also contain teichoic acids (negatively charged). What are some of its functions
- help maintian the cell envelope
- protect from environmental substances
- may bind to host cells
T/F: gram-psitive bacteria do not have a layer of proteins on the surface of peptidoglycan?
False. some gram-positive bacteria have a layer of proteins on the surface of peptidoglycan
List the characterisitics of the periplasmic space of gram-positive bacteria (3).
- Lies between the plasma membrane and the cell wall and is smaller than that of gram-negative bacteria
- Periplasm has relatively few proteins
- enzymes secreted by gram-positive bacteria are called exoenzymes
- aid in degradation of large subunits
Which bacterial cell walls are more complex, gram-positive or gram-negative?
gram-negative cell walls
These bacterial cell walls consist of a thin layer of peptidoglycan surrounded by an outer membrane?
gram-negative bacteria cell walls
Do the cell walls of gram-negative bacteria contain teichoic acids?
no
The outer membrane of gram-negative cell walls have three components, what are they?
- lipids
- lipoproteins
- lipopolysaccharide (LPS)
In gram-negative bacteria peptidoglycan composes what percentage of the cell wall weight?
~5-10%
How does the periplasmic space of gram-negative cell walls differ from that in gram-positive cells?
- may constitue 20-40% of the cell volume
- many enzymes present in the periplasm
- hydrolytic enzymes, transport proteins and other proteins
In gram- negative bacteria the outer membrane lies _______ the thin _______ layer?
outside, peptidoglycan
These lipoproteins in gram-negative bacteria connect the outer membrane to the peptidoglycan layer?
Braun’s lipoproteins
LIst three characteristics of lipopolysaccharide (LPS)
- consists of three parts
- lipid A
- core polysaccharide
- O side chain (O antigen)
- Lipid A is embedded in the outer membrane
- core polysaccharide O side chain extends out from the cell
Name 4 of 6 reasons why LPS is important.
- Contribute to negative charge on the cell surface
- helps to stabilize outer membrane structures
- may contribute to attachment to surfaces and biofilm formation
- creates a permeability barrier
- protection from host defenses (O antigen)
- can act as an endotoxin (lipid A)
Gram-negative outer membrane is ______ permeable than the plasma membrane due to the presence of ______ proteins and ______ proteins?
more, porin, transporter
Which type of environments will cause cell lysis?
Hypotonic environments
Which types of environments will cause plasmolysis?
hypertonic environments
What is plasmolysis?
When the plasma membrane shrinks but the cell wall maintains its shape
What type of environment will cause plasmolysis?
Hypertonic environments
T/F: the cell wall helps to prevent osmotic lysis?
True
Penicillin inhibits ______ synthesis?
Peptidoglycan
Name two characteristics of archaeal cell walls
- They lack peptidoglycan
- some have pseudopeptidoglycan (pseudomurein)
- the cell wall varies from species to species
Define glycocalyx.
- layer consisting of a network of polysaccharides extending from the surface of the cell.
- can include capsules and slime layers
List some characteristics regarding capsules (4).
- usually composed of polysaccharides
- well organized and not easily removed from the cell
- visible in light microscope
- has protective advantages
- resistant to phagocytosis
- protect from dessication
- exclude viruses and detergents
List some characteristics regarding slime layers (2)
- similar to capsules, except diffuse, unorganize, and easily removed
- slime may aid in motility
What is an S Layer?
regularly structured layers of proteins or glycoproteins that self assemble
How do the S layers of gram-negative bacteria and gram-positive bacteria differ?
- Gram-negative bacteria the S layer adheres to the outer membrane
- Gram-positive bacteria the S layer is associated with the peptidoglycan surface
List some functions of the S layer (5).
- protect from ion and pH fluctuations, osmotic stress, ezymes, and predation
- maintains shape and rigidity
- promotes adhesion to surfaces
- protects from host defenses
- potential use in nanotechnology
- S layer spontaneoulsy associates
There are external structures that extend beyond the cell envelope in bacteria that function in protection, attachment to surfaces, horizontal gene transfer, and cell movement. What structures participate in the functions?
- Pilli and fimbriae
- flagella
List some characteristics of fimbriae (3).
- Short, thin, hairlike, proteinaceous appendages (1000/cell)
- can mediate attachment to surfaces
- some (type IV fimbria) are required for twitchin motility or gliding motility that occurs in some bacteria
List some characterisitics of sex pili (3).
- longer, thicker, and less numerous than fimbriae (1-10/cell)
- genes for formation are found on plsmids
- are required for conjugation (mating)
What are flagella and what are their functions?
- Flagella are threadlike, locomotor appendages that extend outward from the plasma membrane and cell wall.
- Functions
- motility and swarming behavior
- attachment to surfaces
- may be virulence factors
What are the three parts of a flagella?
- Filament
- Hook
- Basal body
What are the functions or properties of the three parts of flagella?
- Filament
- extends from cell surface to the tip
- hollow, rigid cylinder of flagellin protein
- Hook
- links filament to basal body
- Basal body
- series of rings that drive flagellar motion
LIst the cahracteristics of flagellar synthesis (3).
- complex process involving many genes and gene products
- new flagellin molecules transported through the hollow filament using typ II-like secretion system
- filament subunits self-assemble with the help of filament cap at tip, not base
There are 5 different types of flagella distrubition, what are they?
- monotrichous
- polar flagellum
- amphitrichous
- lophotrichous
- peritrichous
Cells with monotrichous flagella are characterized by?
one flagellum
cells that have polar flagellum are characterized by?
flagellum at end of cell
Cells with amphitrichous flagella are characterized by?
one flagellum at each end of cell
Cells with lophotrichous flagella are characterized by?
cluster of flagella at one or both ends of the cell
Cells with peritrichous flagella are characterized by?
flagella spread over the entire surface of the cell
Bacteria and archaea can direct their movement several ways. What are some of those ways?
- flagellar movement
- spirochete motility
- twitching motility
- gliding motility
What is chemotaxis?
The movement of cells towards attractants such as nutrients, or away from harmful substances
This type of bacterial flagellar movement will cause the cell to move foward (run)?
counterclockwise rotation
This type of bacterial flagellar movement will cause a disruption in the forward motion (run) and cause the cell to stop and tumble?
Clockwise rotation
The flagellum is a 2 part motor producing torque. What are the 2 components?
- Rotor
- C (FliG protein) ring and MS ring turn and interact with strator
- Stator- Mot A and Mot B proteins
- form channel through plasma membrane
- protons move throught Mot A and Mot B channels using the energy of proton motive force
- torque powers rotation of the basal body and filament
What are some characteristics of Spirochete motility (3)?
- Mutliple flagella from axial fibril which winds around the cells
- flagella remain in peroplasmic space inside outer sheath
- corkskrew exhibits flexing and spinning movements
Twitching and gliding motility may involve ______ ____ _____ and ______?
type IV pili, slime
This type of movement involves short, intermittent, jerky motions?
Twitching
This type of movement involves smooth movements?
gliding
In the presence of an attractant tumbling frequency is _______ and the frequency of runs in the direction of the attractant is _______?
Decreased, increased
T/F: the behavior of bacterium is not altered by temporal concentration of a chemical?
False. the behavior of bacterium IS altered by temporal concentraion of a chemical
What is an endospore?
A complex dormant structure fromed by some bacteria (mother cell)
The bacterial endospore is resistanrt to numerous environmentla conditions such as?
- heat
- radiation
- chemicals
- desiccation
List the components of the stucture of an endospore.
- spore surrounded by this coverin called exosporium
- thick layers of protein form th epsore coat
- cortex, beneath the coat, composed of thick peptidoglycan
- core has nucleoid and ribosomes
What are some reasons that endosores are so resistant?
- calcium (complexed with dipicolinic acid)
- small, acid-soluble, DNA-binding proteins (SASPs)
- dehydrated core
- Spore coat and exosporium provide protection
- DNA repair enzymes
What is sporulation?
The process of endospore formation
When does sporulation occur?
Normally commences when growth ceases due to a lack of nutrients