microbiology exam 2 chapter 8 part 1 Flashcards
What initiates chromosome replication in bacteria?
DnaA binding to specific sequences within the oriC region leads to unwinding and loading of the replisome.
Most active when linked to ATP (DnaA–ATP).
How is DnaA–ATP inactivated?
Competition for oriC binding
Repression of dnaA expression
Titration of DnaA–ATP away from oriC
Inactivation of DnaA–ATP
What happens after replication initiation?
Only the parental strand is methylated.
This facilitates competition for origin binding between DnaA–ATP and SeqA.
Hemimethylated oriC is strongly bound by SeqA, blocking DnaA–ATP.
How is genome replication in fast-growing cells different?
Circular genome replication is bidirectional from the origin.
E. coli’s genome replication takes 40 minutes but is independent of generation time (can be as short as 20 minutes).
What happens if a cell’s doubling time is shorter than genome replication time?
Multiple DNA replication forks are present.
A new round of replication begins before the previous one is completed.
Some genes may be present in multiple copies.
What is chromosome segregation in bacteria?
Ensures daughter cells get a copy of the genome and allows septum formation.
In many bacteria, the Par (partitioning) system _____ distributes chromosomes and plasmids.
equally
What are Fts proteins?
Fts proteins are essential proteins involved in cell division, specifically in binary fission.
What is the Divisome?
The Divisome is a complex of several essential proteins, including Fts proteins, that are involved in bacterial cell division
What is the role of FtsZ protein in binary fission?
FtsZ protein is crucial in binary fission, acting similarly to tubulin in eukaryotic cell division.
To which protein is FtsZ related
FtsZ is related to tubulin, a protein involved in eukaryotic cell division.
In which organisms is FtsZ found?
FtsZ is found in virtually all Archaea and in bacteria.
Are all Fts proteins found in all organisms?
No, other Fts proteins are found only in Bacteria, not in Archaea or eukaryotes.
What do Fts proteins form during cell division?
Fts proteins interact to form the divisome, the cell division apparatus
How does divisome formation begin in rod-shaped cells?
Divisome formation begins with the attachment of FtsZ molecules around the center of the cell, forming a ring that becomes the cell-division plane.
What other divisome proteins are attracted to the FtsZ ring
Other divisome proteins, including FtsA and ZipA, are attracted to the FtsZ ring.
What is the function of ZipA in the divisome?
ZipA is an anchor that connects the FtsZ ring to the cytoplasmic membrane.
What is the role of FtsA in the divisome?
FtsA is related to actin and helps recruit FtsZ and other divisome proteins, connecting the FtsZ ring to the membrane.
When does the divisome form during cell division?
The divisome forms about three-quarters of the way into cell division.
What is the role of Fts proteins in the divisome?
Fts proteins are needed for peptidoglycan synthesis during cell division.
What is the function of FtsI?
FtsI is a penicillin-binding protein involved in peptidoglycan synthesis, and it is inhibited by the antibiotic penicillin.
What does the divisome orchestrate during cell division?
The divisome orchestrates the synthesis of new cytoplasmic membrane and cell wall material (division septum), enabling the cell to divide.
hen does DNA replicate in relation to FtsZ ring formation?
DNA replicates before the FtsZ ring forms
What blocks the formation of the FtsZ ring before nucleoid segregation?
: The nucleoids (chromosomes) block the formation of the FtsZ ring before they segregate.
What is the role of MinC, MinD, and MinE proteins?
MinC, MinD, and MinE proteins guide the FtsZ ring to the cell’s midpoint.
What proteins mediate the separation of chromosomes to daughter cells?
FtsK and other proteins mediate the separation of chromosomes to daughter cells.
What happens when FtsZ depolymerizes during cell division?
When FtsZ depolymerizes, it triggers the inward growth of wall materials to form the septum.
What is the function of FtsZ’s hydrolysis of GTP during cell division?
FtsZ hydrolyzes GTP to provide energy for the cell division process.
What is MreB’s role in bacterial cell shape?
MreB is the major shape-determining factor in Bacteria and some Archaea, helping to define cell morphology.
What structure does MreB form in the cell?
MreB forms a simple cytoskeleton with patch-like filaments just below the cytoplasmic membrane.
How does MreB contribute to cell wall growth?
MreB recruits other proteins for cell wall growth, forming the elongasome, which aids in cell shape maintenance.
What happens if MreB is inactivated in bacilli?
inactivation of MreB causes bacilli to become cocci (spherical).
What do most coccoid bacteria lack
Most coccoid bacteria lack MreB and RodZ proteins.
How do MreB filaments contribute to cell division in rod-shaped bacteria?
MreB filaments move from one side to another, directing peptidoglycan synthesis, which allows new cell wall formation at several points (rod shape) instead of just one location (cocci).
How does cell wall growth occur in rod-shaped cells?
In rod-shaped cells, cell wall growth occurs at several points along the length of the cell.
How does cell wall growth occur in cocci?
In cocci, cell walls grow in opposite directions outward from the FtsZ ring.
What must happen to preexisting peptidoglycan for new peptidoglycan to be inserted? A
Preexisting peptidoglycan must be temporarily severed to allow the insertion of newly synthesized peptidoglycan.
hat must all bacterial cells do in relation to peptidoglycan?
All bacterial cells must synthesize new peptidoglycan and export it outside the cytoplasmic membrane.
What is required for the synthesis of new peptidoglycan?
The synthesis of new peptidoglycan requires the controlled cutting of existing peptidoglycan and the simultaneous insertion of precursors.
What role does bactoprenol play in peptidoglycan synthesis?
Bactoprenol plays a major role in precursor insertion, transporting peptidoglycan precursors across the membrane.
What is the structure of bactoprenol?
Bactoprenol is a hydrophobic C55 alcohol.
What is Lipid II?
Lipid II is a complex in which bactoprenol is bonded to the N-acetylglucosamine, N-acetylmuramic acid, and pentapeptide peptidoglycan precursor.
how does bactoprenol transport peptidoglycan precursors?
Bactoprenol transports peptidoglycan precursors across the membrane through the action of the flippase enzyme.
What is the role of Lipid II in peptidoglycan biosynthesis?
Lipid II interacts with transglycosylases, which insert peptidoglycan precursors into growing points and catalyze the formation of glycosidic bonds.
How is bactoprenol involved in precursor transport?
Bactoprenol is recycled for precursor transport after it has delivered peptidoglycan precursors across the membrane.
hat is the function of autolysins in peptidoglycan biosynthesis?
Autolysins make gaps in the peptidoglycan by hydrolyzing the bond between N-acetylglucosamine and N-acetylmuramic acid.
hat happens after autolysins make gaps in peptidoglycan?
Peptidoglycan precursors are added across the gaps, which are observed as wall bands.
Why must peptidoglycan biosynthesis be highly coordinated?
Peptidoglycan biosynthesis must be highly coordinated to avoid autolysis (self-digestion of the cell wall).
What is transpeptidation in peptidoglycan biosynthesis?
Transpeptidation is the final step in peptidoglycan synthesis, where peptide cross-links are formed between muramic acid residues in adjacent glycan chains.
what is FtsI’s role in peptidoglycan biosynthesis in E. coli?
In E. coli, FtsI is a transpeptidase that catalyzes the transpeptidation process.
How does penicillin affect transpeptidation?
Penicillin inhibits FtsI (the transpeptidase), preventing the formation of peptide cross-links in peptidoglycan.
What happens if autolysins continue to be active during peptidoglycan biosynthesis?
Continued activity of autolysins weakens the peptidoglycan, causing the cell to burst.
What are endospores in bacteria?
Endospores are highly resistant, dormant forms of bacteria that are formed in response to unfavorable environmental conditions, allowing the bacteria to survive harsh conditions.
what is the role of endospores in bacterial survival?
Endospores protect the bacterial genome from damage due to extreme heat, desiccation, chemicals, and radiation, and can remain dormant for extended periods until conditions become favorable again.
What are Anabaena heterocysts?
Heterocysts are specialized cells in the cyanobacterium Anabaena that fix nitrogen, allowing the organism to survive in nitrogen-poor environments.
Why are heterocysts important for Anabaena?
Heterocysts provide an anaerobic environment for nitrogen fixation by the enzyme nitrogenase, which is sensitive to oxygen.
What are biofilms?
Biofilms are complex communities of bacteria that adhere to surfaces and are embedded in a protective extracellular matrix, often forming on natural or artificial surfaces.
What is the advantage of biofilm formation for bacteria?
Biofilm formation provides protection from environmental stressors, such as antibiotics and the immune system, and enhances bacterial communication and nutrient availability.
What triggers endospore formation?
adverse conditions cause vegetative cells to convert into spores.
When does germination occur?
Germination occurs when favorable conditions return.
What is the result of asymmetric division in endospore formation?
It results in a smaller endospore surrounded by a larger mother cell.
What happens to the mother cell after endospore development?
The mother cell bursts after the spore is fully developed.
What triggers endospore formation?
Adverse external conditions like starvation, desiccation, and inhibitory temperatures.
How does the cell monitor the environment for endospore formation?
Through five sensor kinases working in a phosphotransfer relay system.
What happens after the phosphorylation of sporulation factors?
It leads to the successive phosphorylation of factors, culminating with Spo0A.
What happens when Spo0A is highly phosphorylated?
Sporulation proceeds.
Are endospores metabolically active?
No, endospores are not metabolically active.
How long can endospores remain dormant?
Endospores can remain dormant for years.
Can endospores sense and respond to environmental changes?
Yes, endospores can sense nutrients and favorable conditions.
What does germination allow?
Germination allows conversion back to vegetative cells.
What are germinant receptors (GR) in endospores?
Germinant receptors are within the inner membrane, clustered in a “germinosome” that senses and binds nutrients.
What are the three stages of endospore germination?
Activation, germination, and outgrowth.
What triggers activation of endospore germination?
increased temperatures help trigger activation.
What happens during the germination stage?
Cortex lytic enzymes (CLE) degrade the endospore cortex peptidoglycan, and the cortex is removed.
What is the result of the cortex removal during germination?
the endospore becomes completely hydrated and can become metabolically active.
What happens during Stage III: Outgrowth of endospore germination?
Metabolism returns to near-normal rates, starting the cell cycle and binary fission.
What occurs during cell elongation in outgrowth?
The vegetative cell escapes from the spore coats.
what is required for the outgrowth stage?
Increased gene expression for energy-generating processes.
Which organism causes anthrax bioterrorism?
Bacillus anthracis.
Which organism causes colitis?
Clostridioides difficile.
Which organism causes tetanus?
Clostridium tetani.
Which organisms can cause food poisoning?
Bacillus cereus and Clostridium perfringens.
Which organism causes gas gangrene?
Clostridium perfringens.
Which organism causes botulism (foodborne and wound)?
Clostridium botulinum
