Bacteria Flashcards
Which of the following is not a function of the membrane proteins?
Transportation, Fluidity, Sensors, Secretions + Osmosis
Fluidity
For bacteria, the proton driven ATP synthase is located in the mitochondria. T/F
False, it is located in the cell membrane.
What are the four membrane lipids found in bacteria?
- cardiolipin
- plamitic and oleic acid
- cyclopropane fatty acids
- hopanoids
Match the following terms:
1. cardiolipin
2. palmitic and oleic acid
3. cyclopropane fatty acid
4. hopanoids
a) similar to cholesterol; stabilizes membrane in all temperatures
b) adds fluidity to membrane in cold temperatures
c) binds to certain environmental stress proteins in the cell poles. found in bacteria only
d) stiffens cell membrane
Cardiolipin: binds to certain environmental stress proteins in the cell poles. found in bacteria only
Palmitic and oleic acid: adds fluidity to membrane in cold temperatures
Cyclopropane fatty acid: stiffens cell membrane
Hopanoids: similar to cholesterol; stabilizes membrane in all temperatures
The three main functions of the bacterial cell membrane are:
Briefly describe each one!
- Permeability barrier - gateway for transportation + prevents leakage
- Protein anchor - hold transport proteins in place
- Energy conservation - generation of proton motive force
The majority of bacterial cell membrane lipids have the following basic structure: a ________ molecule linked to two _______ acids via
an ______ bond, and a _________ head group.
Glycerol, fatty, ester, phosphoryl
How does the cell wall protect the bacteria from a hypotonic solution (fresh water)?
Cell wall counteracts OSMOTIC PRESSURE to prevent swelling and lysis.
Bacterial cell wall is made of a single interlinked molecule called the peptidoglycan. T/F
True!
What is the peptidoglycan structure composed of?
Alternating modified glucose
- NAG (N-acetylglucosamine) and NAM (N-acetylmuranic acid) in b-1,4 linkages
Amino acids
- L-alanine, D-alanine, D-glutamic acid, and either L-lysine or diaminopimelic acid (DAP)
Why is human secretion a major defence against bacterial infections?
Contains lysozyme which breaks the B-1,4 linkages of the peptidoglycan
Why are enzymes involved in the formation of peptidoglycan a great target for antibiotics? Describe how penicillin and vancomycin works.
enzymes involved in the formation of peptidoglycan are a great target for antibiotics because peptidoglycan is unique to bacteria!
penicillin inhibits transpeptidase which cross-links the peptides
vancomycin prevents cross-bridge formation by binding to the substrate of transpeptidase (the terminal D-Ala-D-Ala dipeptide)
To form a gram (+) cell wall, there is a ________ between the two peptidoglycans.
To form a gram (-) cell wall, there is a ________ between the two peptidoglycans.
Pentaglycine interbridge
A peptide crosslink; a direct bridge
While the gram-positive is a thick layer located on top of the plasma membrane, the gram-negative is….
a thin layer, sandwiched between the outer and inner membrane
Why is the gram-positive a thick layer?
Because it has multiple layers of peptidoglycan.
What are teichoic acids and where are they found?
A negatively charged glycopolymer that generates proton motive force
Helps with rigidity and cell shape
Protects against high temps + high [salt] + antibiotics like b-lactams
Found in a gram-positive cell wall
How are lipoteichoic acids different than teichoic acids?
Lipotechoic acids are covalently bound to membrane lipids
What do lipopolysaccharides (LPS) consist of and where are they found?
LPS consists of core
polysaccharide:
• O-polysaccharide
• and lipid A (which is toxic to us, as the immune system reacts violently to it)
Found in a gram-negative cell wall
What are the 4 types of stains? Briefly describe each one
- Gram stain (most widely used, gram + is blue, gram - is pink)
- Acid-fast stain (carbolfuchsin used to stain Mycobacterium)
- Spore stain (malachite green used to detect spores)
- Negative stain (colours the bg, makes spores more visible)
Match the following terms:
- Bactericidal
- Bacteriostatic
- Nosocomial infection
A. Requires hospital care
B. Kills bacteria
C. Inhibits growth
Bactericidal: kills bacteria
Bacteriostatic: inhibits growth
Nosocomial infection: requires hospital care
What is resistance and what causes it?
Genetically acquired trait that allows bacteria to not be killed by an antibiotic, which can be shared with other microbes.
Usually a result of widespread of use of antibiotics
What are glycocalyces? What are the different types?
Cell surface structures made of polysaccharide layers. Not strong 4 cell wall.
Capsules + Slime layer are the two different types.
Define capsules
tightly attached polysaccharide matrix
Define slime layer and its functions
loosely attached glycocalyces
assists in attachment to surface + development & maintenance of biofilms, protects against phagocytosis, and prevents dehydration
What is a S layer? What are its functions?
A protective layer found in bacteria + archaea, made of protein/glycoprotein.
Contains cell shape + protects from osmotic stress.
What are fimbriae & pili? What are their functions?
Filamentous protein structures
Fimbriae enable organisms to stick to surfaces or
form pellicles.
Pili are longer and found less;
- CONJUGATIVE/SEX pili facilitate genetic exchange used by gram-negative bacteria.
- TYPE IV pili adhere to host tissues n support twitching motility.
Match the following specialized structures with their definition:
- Thylakoids
- Carboxysomes
- Gas vesicles
- Magnetosome
- Cell inclusions
- Stalks
- Holdfasts
A. Made of protein, lipid + iron which help orient cell during movement
B. Membrane embedded extensions of the cytoplasm
C. Adhesion factors
D. Extensively folded membranes in photosynthetic materials
E. Protein-bound structures that increase buoyancy
F. Energy reserves/ Carbon reservoirs enclosed by thin membrane, which decrease osmotic stress.
G. Polyhedral bodies with RUBISCO for CO2 fixation
Thylakoids: extensively folded membranes in photosynthetic materials
Carboxysomes: polyhedral bodies with RUBISCO for CO2 fixation
Gas Vesicles: protein-bound structures that increase buoyancy
Magnetosome: Made of protein, lipid + iron which help orient cell during movement
Cell inclusions: Energy reserves/ Carbon reservoirs enclosed by thin membrane, which decrease osmotic stress.
Stalks: Membrane embedded extensions of the cytoplasm
Holdfasts: Adhesion factors
What are the main functions of bacterial cytoskeleton?
- shapes the morphology of the cell
- helps move molecules to the right location
- implicated in cell division
Briefly describe the ParM system of the bacterial cytoskeleton:
It segregates a dividing chromosome to both polls of the cell and also segregates plasmids.
What are the 3 types of bacterial cytoskeleton proteins and their functions?
- FtsZ: TUBULIN-LIKE PROTEIN that assists in cell division + controls the diameter of the cell
- MreB: ACTIN LIKE PROTEIN that maintains the rod shape of the cell
- Crescentin: FILAMENT LIKE PROTEIN that maintains the curve shape of the cell
What is a main difference between eukaryotes and prokaryotes in terms of DNA replication?
Prokaryotes synthesize RNA + proteins continually while the DNA is getting replicated.
Translation begins before transcription is complete for Eukaryotes.
Briefly describe how cell division by septation occurs, also the role of FtsZ and Divisome.
After DNA synthesis terminates, a septum grows inward from the sides of the cell.
FtsZ circles around the septum and directs its growth. When FtsZ’s ring contracts, the two daughter cells separate.
Divisome is the protein complex that manages septation, which Ftsz is a part of.
Septation requires rapid _______ of all ______ components, including membranes + cell wall.
Septation is coordinated with ____ ________.
Biosynthesis
Envelope
DNA replication
Briefly describe how DNA replication occurs in a bacterial cell.
- DNA at origin unzips, and two replication forks form (now 2 sites of ori)
- Replisomes (one at each fork with 2 DNA polymerases) synthesize daughter chromosomes bidirectionally.
- As the termination site is replicated, the 2 forks separate from DNA.
- Completing of replication triggers septum formation.
If a new round of DNA replication began before the first one terminated, how many polymerases would be required? Why?
12
Originally, it has two replisomes with 4 DNA polymerases because there was ONE SITE OF ORI. If a new round of DNA replication begins, two new replisomes at each site of the TWO ori form. This means 8 DNA polymerases.
8 + 4 = 12.
Even symmetrical bacteria have underlying physical + chemical asymmetry, but other species develop different structures at either pole. Their cell division results in two kinds of daughter cells:
- Stationary (sessile)
- Mobile (swarmer)
What is the difference between stationary and mobile daughter cells?
Stationary cells, aka sessile cells, are stalked cells with a stalk and a holdfast attached to them. These cells can divide while mobile cells can not.
What are extracellular membrane vesicles and what are their 3 functions?
Extracellular membrane vesicles contain bits of cytoplasm such as proteins and nucleic acids.
Their functions:
1. attractors of partner heterotrophs
2. phage decoys (virus can attach to vesicles instead of bacteria)
3. Vehicles for DNA transfer
What are nanotubes and why are they so important?
Membrane extensions that merge directly with neighbouring organisms.
They allow bacteria to share proteins + mRNA under hostile conditions.
Bacterial nanotubes are sensitive to detergent treatment suggesting they are composed primarily of:
Phospholipids
What are Flagellas?
Long, thin, helical reversible rotating machine which increase/decrease rotational speed relative to proton motive force.
What are the four different types of arrangements of flagellas?
Monotrichous (one flagella)
Amphitrichous (two)
Lophotrichous (four)
Peritrichous (a lot)
For chemotaxis, attractants cause ____ rotation, where flagella ______ ______, causing a _____ motion.
CCW, bundle together, RUN
For chemotaxis, repellents cause ____ rotation, where flagellar bundle ______ ______, causing a _____ motion, which causes the bacteria to stop and _______ ________.
CW, falls apart, TUMBLE & change direction.
Match the following terms:
- Taxis
- Aerotaxis
- Osmotaxis
- Chemoreceptors
A. directed movement in response to oxygen
B. sense attractants/repellents
C. directed movement in response to chemical/physical gradients
D. directed movement in response to ionic strength
Taxis - directed movement in response to chemical/physical gradients
Aerotaxis - directed movement in response to oxygen
Osmotaxis - directed movement in response to ionic strength
Chemoreceptors - sense attractants/repellents
What are Endospores?
gram (+) bacterial cells that protect the bacterial genome in a DORMANT STATE where the env conditions are bad.
They are resistant to extreme temps + radiation with no growth/metabolic activity.
They can become live cells when env is good.
Match the following terms:
- Calcium-dipicolinic acid
(DPA) complex - Acid-soluble spore proteins (SASP)
- Endosporulation/sporulation
- Major form of asymmetrical growth
A. Found in the core of endospores, which bind + protect DNA and function as carbon and energy source for outgrowth.
B. Process where endospores are formed.
C. Endospore formulation
D. Helps endospores to cope with dehydration and stabilize DNA.
- D
- A
- B
- C
What are the four layers of endospores in order where the outer layer is #1?
- Exosporium
- Spore coat
- Core wall
- Cortex
Sporulation in 6 steps:
- Replication + stretching DNA into a long axial filament
- Septation divides the cell into a foreshore and a mother cell
- Mother cell membrane engulfs foreshore + foreshore forms additional membranes
- Mother cell chromosome destruction + a cortex is formed around the spore
- Deposition of coat proteins
- Mother cell releases spore
