Fts Proteins, Cell Division, and Morphology
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Questions and Answers

Which of the following is NOT a known function of the S-layer in archaea?

  • Providing structural support to the cell.
  • Facilitating genetic exchange between cells. (correct)
  • Forming a pseudo-periplasmic space.
  • Acting as a molecular sieve, controlling molecule passage.

A bacterium is found to be resistant to desiccation and capable of forming biofilms. Which external structure is most likely contributing to these characteristics?

  • Pili
  • S-Layer
  • Flagella
  • Capsule (correct)

Type IV pili are involved in which of the following functions?

  • Carbon storage.
  • Twitching motility. (correct)
  • Conjugation.
  • Sulfur oxidation.

A bacterium is observed to form a thin sheet of cells on the surface of a liquid medium. Which structure is most likely responsible for this phenomenon?

<p>Fimbriae (A)</p> Signup and view all the answers

Which of the following is a function uniquely associated with pili, rather than fimbriae?

<p>Genetic exchange between cells (D)</p> Signup and view all the answers

A bacterial cell is found to contain granules of poly-beta-hydroxybutyric acid (PHB). What is the function of these granules?

<p>Storage of carbon and energy (A)</p> Signup and view all the answers

Elemental sulfur globules found in the periplasm of some bacteria are associated with which metabolic process?

<p>Sulfur oxidation (C)</p> Signup and view all the answers

A researcher discovers a new bacterial species that thrives in extremely dry conditions. Which external structure would most likely contribute to its survival?

<p>A thick capsule (A)</p> Signup and view all the answers

Which of the following structures are filamentous protein structures?

<p>Pili and fimbriae (B)</p> Signup and view all the answers

If a bacterium lost its ability to produce MreB and Crescentin, what change in morphology would be expected?

<p>The cell would become more coccus-shaped. (C)</p> Signup and view all the answers

In nitrifying bacteria, what is the primary function of the internal membrane systems?

<p>To house key enzymes involved in nitrification. (B)</p> Signup and view all the answers

What is the role of ammonia monooxygenase in the process of nitrification?

<p>Oxidizing ammonia to hydroxylamine. (B)</p> Signup and view all the answers

Which cellular structure is typically connected to the cytoplasmic membrane in phototrophic, nitrifying, and methanotrophic bacteria?

<p>Internal membranes. (C)</p> Signup and view all the answers

Why do certain bacteria, such as nitrifying bacteria, benefit from having extensive internal membrane systems?

<p>Key enzymes are membrane-bound, so more membrane equates to more enzyme. (B)</p> Signup and view all the answers

What is the function of nitrite oxidase in nitrifying bacteria?

<p>Oxidizes nitrite to nitrate. (B)</p> Signup and view all the answers

Nitrification is typically carried out by two groups of bacteria. What are the substrates for each group?

<p>Ammonia oxidizers using ammonia, and nitrite oxidizers using nitrite. (C)</p> Signup and view all the answers

Which of the following bacterial groups is known to possess a unique internal membrane structure called the annamoxosome?

<p>Planctomycetes (B)</p> Signup and view all the answers

How do internal membranes in bacteria like phototrophs and nitrifiers differ from organelles like mitochondria in eukaryotes?

<p>Bacterial internal membranes are invaginations of the cytoplasmic membrane, whereas eukaryotic organelles are separate compartments. (D)</p> Signup and view all the answers

A researcher is studying a new bacterium isolated from a freshwater lake and observes that it contains numerous internal membrane structures. Based on the information, which metabolic process is this bacterium most likely involved in?

<p>Nitrification (D)</p> Signup and view all the answers

If a bacterium loses its ability to produce nitrite oxidase, what direct consequence would this have on the nitrification process?

<p>Prevent the conversion of nitrite to nitrate. (B)</p> Signup and view all the answers

Which of the following is the primary function of chlorosomes in green sulfur bacteria?

<p>Light harvesting and transfer to the reaction center. (D)</p> Signup and view all the answers

What triggers the formation of endospores in bacteria such as Bacillus and Clostridium?

<p>Depletion of essential nutrients like carbon or nitrogen. (C)</p> Signup and view all the answers

Which of the following best describes the function of carboxysomes found in some chemolithotrophs and photolithotrophs?

<p>They house enzymes involved in carbon dioxide ($CO_2$) fixation. (D)</p> Signup and view all the answers

What is the primary purpose of gas vesicles in planktonic bacteria?

<p>To regulate buoyancy, aiding in vertical positioning in aquatic environments. (B)</p> Signup and view all the answers

Magnetosomes enable magnetotactic bacteria to perform which of the following actions?

<p>Migration along magnetic field lines. (C)</p> Signup and view all the answers

How do chlorosomes contribute to the survival strategy of bacteria in low-light environments?

<p>By capturing and concentrating light energy, then directing it to the reaction center. (B)</p> Signup and view all the answers

What is a key characteristic that distinguishes endospores from vegetative bacterial cells?

<p>Endospores are highly resistant to heat, radiation, and harsh chemicals. (B)</p> Signup and view all the answers

Why might the ability to form carbonate minerals be advantageous to certain bacteria?

<p>The mineralization process can contribute to carbon sequestration and influence local geochemistry. (A)</p> Signup and view all the answers

Poly-$β$-hydroxyalkanoates (PHAs) are an example of what type of storage product in bacteria?

<p>Energy reserves (A)</p> Signup and view all the answers

A bacterium is discovered in an ancient halite deposit. What characteristics would suggest it is related to endospore-forming bacteria?

<p>A cell structure highly resistant to heat, chemicals, and age. (B)</p> Signup and view all the answers

Which of the following is the primary function of FtsZ protein in prokaryotic cell division?

<p>Forming a ring-like structure around the center of the cell to initiate division. (A)</p> Signup and view all the answers

How does the Min system (MinC, MinD, and MinE proteins) contribute to the correct placement of the FtsZ ring during cell division?

<p>By inhibiting FtsZ ring formation at the poles of the cell, ensuring it forms at the midpoint. (B)</p> Signup and view all the answers

What would most likely happen if a bacterium lost the ability to produce ZipA?

<p>The FtsZ ring would not be able to anchor to the cytoplasmic membrane. (D)</p> Signup and view all the answers

MreB is a major shape-determining factor in rod-shaped bacteria. What cellular process does MreB influence to maintain cell shape?

<p>Recruiting proteins for cell wall growth in a specific pattern. (C)</p> Signup and view all the answers

A bacterium with a mutation in the gene encoding crescentin would most likely exhibit which phenotype?

<p>A straight or altered cell shape instead of a curved one. (C)</p> Signup and view all the answers

How does FtsA contribute to cell division?

<p>It is an ATPase. (A)</p> Signup and view all the answers

A newly discovered bacterium is coccus-shaped. Based on what is known about bacterial cytoskeletal elements, which protein would you expect it not to possess?

<p>MreB (C)</p> Signup and view all the answers

If MinCD is non-functional, what is the most likely outcome?

<p>The FtsZ ring will form at the poles of the cell, leading to improper division. (B)</p> Signup and view all the answers

A bacterium has a mutation that prevents FtsK from functioning correctly. What cellular process will be most directly affected?

<p>Chromosome separation. (A)</p> Signup and view all the answers

Which protein involved in bacterial cell division has structural homology to tubulin in eukaryotes, and what does this suggest about its function?

<p>FtsZ, suggesting a role in cell division. (A)</p> Signup and view all the answers

Flashcards

Internal Membranes in Bacteria

Internal membranes connected to the cytoplasmic membrane in some bacteria, increasing surface area for membrane-bound enzymes.

Nitrification

The lithotrophic oxidation of ammonia to nitrate, typically occurring in two steps.

Ammonia Oxidizers

Bacteria that oxidize ammonia to nitrite as the first step in nitrification.

Nitrite Oxidizers

Bacteria that oxidize nitrite to nitrate as the second step in nitrification.

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Ammonia Monooxygenase

An enzyme that oxidizes ammonia (NH3) to hydroxylamine (NH2OH) in nitrifying bacteria.

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Nitrite Oxidase

An enzyme that oxidizes nitrite (NO2-) to nitrate (NO3-) in nitrifying bacteria.

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Anammoxosome

Internal membrane structures found in Planctomycetes involved in anaerobic ammonia oxidation.

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Planctomycetes internal membranes

Some Planctomycetes have other internal membrane structures.

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Cell Morphology Determinants

Proteins (MreB and Crescentin) that determine the shape of a cell.

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aPBP and bPBP Function

Coordinate peptidoglycan synthesis through transpeptidation and transglycosylation.

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S-Layers

Common archaeal cell wall component, made of protein or glycoprotein, providing support and acting as a molecular sieve.

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Capsule/Exopolysaccharide Functions

Attachment, biofilm formation, protection from grazing/immune systems/antibiotics, and prevention of dessication.

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Fimbriae Function

Enable organisms to stick to surfaces and form pellicles.

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Pili Function

Facilitate genetic exchange (conjugation); support twitching motility.

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PHA (Polyhydroxyalkanoates)

Lipids that store carbon/energy.

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Glycogen Function

Storage for carbon/energy.

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Polyphosphate Granules

Inorganic phosphate storage.

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Sulfur Globules

Elemental sulfur in periplasm that can be oxidized to sulfate.

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Carbonate Minerals

Intracellular granules of barium, strontium and magnesium.

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Chlorosomes

Light-harvesting antennae found in green sulfur bacteria (GSB) and green non-sulfur bacteria (GNSB), allowing growth at low light intensities.

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Carboxysomes

Specialized protein-bound compartments that contain RubisCO enzyme for CO2 fixation in some chemolithotrophs and photolithotrophs.

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Gas Vesicles

Structures that provide buoyancy in planktonic bacteria by decreasing cell density.

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Magnetosomes

Magnetic iron oxide crystals within cells, enabling magnetotaxis (migration along magnetic field lines).

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Endospores

Differentiated, dormant cells resistant to heat, radiation, and harsh chemicals, formed when growth ceases.

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Magnetotaxis

Migration along magnetic field lines.

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Rubisco

Key enzyme involved in CO2 fixation

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Chlorobaculum tepidum

Serve as light antennae and allow the bacteria to grow at low light intensities.

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Endospores

Highly differentiated cells resistant to heat, harsh chemicals, and radiation.

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Fts Proteins

Proteins essential for cell division in prokaryotes, interacting to form the divisome.

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Divisome

A cell division apparatus in prokaryotes formed by interacting Fts proteins.

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FtsZ

Forms a ring around the center of the cell during division; has structural homology to tubulin in eukaryotes

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ZipA

An anchor protein that connects the FtsZ ring to the cytoplasmic membrane.

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FtsI

A peptidoglycan biosynthesis protein involved in cell wall synthesis during division.

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FtsK

Assists in the separation of chromosomes during cell division.

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FtsA

An ATPase protein involved in cell division.

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MinCD

Inhibit the formation of the FtsZ ring, preventing cell division at the poles.

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MinE Function

Oscillates from pole to pole, sweeping MinCD aside to allow FtsZ ring formation at mid-cell.

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Crescentin

Shape-determining protein in curved cells; organizes into filaments on the concave face.

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Study Notes

Fts Proteins and Cell Division

  • Prokaryote membranes play a role in replication
  • Fts proteins are essential for cell division in all prokaryotes
  • Fts proteins interact to form the divisome, the cell division apparatus
  • FtsZ forms a ring around the center of the cell
  • FtsZ has structural homology to tubulin in eukaryotes
  • ZipA is an anchor that connects the FtsZ ring to the cytoplasmic membrane
  • Ftsl is a peptidoglycan biosynthesis protein
  • FtsK assists in chromosome separation
  • FtsA is an ATPase
  • MinCD inhibits the formation of the FtsZ ring
  • MinE oscillates from pole to pole, sweeping MinCD aside
  • When the cell becomes very long, there is little MinCD in the middle of the cell

Determinants of Cell Morphology

  • Prokaryotes can contain a simple cell cytoskeleton
  • Crescentin is a shape-determining protein found in curved cells
  • Crescentin organizes into filaments approximately 10 nm wide that localize on the concave face of curved cells
  • MreB is a major shape-determining factor in prokaryotes
  • MreB forms a simple cytoskeleton with patch-like filaments around the inside of the cell below the cytoplasmic membrane in Bacteria and some Archaea
  • MreB is not found in coccus-shaped bacteria
  • MreB recruits other proteins for cell wall growth to group into a specific pattern
  • Rod A and class A and B penicillin-binding proteins (aPBP and bPBP) coordinate to synthesize new peptidoglycan transpeptidase and transglycosylase

S-Layers of Archaea

  • S-Layers are common cell wall components among Archaea and some bacteria
  • S-layers consist of a protein or glycoprotein monolayer
  • S-layers act as structural support, molecular sieves, and to form a pseudo-periplasmic space

Capsule/exopolysaccharide/glycocalyx/slime layer

  • Capsules/exopolysaccharides/glycocalyx/slime layers facilitate attachment to surfaces and biofilm formation
  • Capsules/exopolysaccharides/glycocalyx/slime layers provide protection from grazing, immune systems, and antibiotics
  • Capsules/exopolysaccharides/glycocalyx/slime layers provide protection from desiccation

Fimbriae and Pili

  • Fimbriae and pili are filamentous protein structures ~2-10 nm wide
  • Fimbriae enable organisms to stick to surfaces or form pellicles, which are thin sheets of cells on a liquid surface
  • Pili are typically longer, thicker, and fewer in number per cell than fimbriae
  • Conjugative pili facilitate genetic exchange between cells through conjugation
  • Type IV pili adhere to host tissues and support twitching motility in bacteria like Pseudomonas and Moraxella

Inclusion Bodies

  • Inclusion bodies serve as carbon/energy storage polymers
    • PHA (polyhydroxyalkanoates) are a family of lipids that includes PHB (poly-beta-hydroxybutyric acid)
    • Glycogen
  • Polyphosphate granules provide inorganic phosphate storage
  • Sulfur globules contain elemental sulfur in the periplasm that can be oxidized to sulfate (SO42-)
  • Carbonate minerals facilitate biomineralization of barium, strontium, and magnesium

Protein-bound compartments

  • Chlorosomes
  • Carboxysomes

Chlorosomes

  • Chlorosomes are light antennae, allowing bacteria to grow at low light intensities
  • Bchl c, d, or e capture light and direct it to Bchl a in the Reaction Center (RC), where photosynthesis occurs
  • Chlorosomes are present in Chloroflexi (GNSB) and Chlorobi (GSB)

Carboxysomes

  • Obligate chemolithotrophs and photolithotrophs possess special structures that house Calvin cycle enzymes (carboxysomes)
  • RubisCO is the key enzyme involved in CO2 fixation

Gas Vesicles

  • Gas vesicles regulate buoyancy in some planktonic bacteria

Magnetosomes

  • Magnetosomes contain magnetic iron oxides
  • Magnetosomes allow for magnetotaxis, which is migration along magnetic field lines

Endospores

  • Endospores are highly differentiated cells resistant to heat, harsh chemicals, and radiation
  • Endospores represent a "dormant" stage of the bacterial life cycle
  • Endospores are ideal for dispersal via wind, water, or animal gut
  • Endospores are only present in some Gram-positive bacteria like Bacillus and Clostridium
  • Endospores are only formed when growth ceases due to a lack of an essential nutrient such as carbon or nitrogen
  • Endospores can remain dormant for years but convert rapidly back to being a vegetative cell

Internal Membranes

  • Internal membranes are found in phototrophic, nitrifying, and methanotrophic bacteria
  • Membranes are usually connected to the cytoplasmic membrane, so they are invaginations rather than separate compartments
  • Key enzymes for these bacteria are membrane-bound, so more membrane equates to more enzymes

Nitrifying Bacteria

  • Nitrification, the lithotrophic oxidation of ammonia to nitrate, usually occurs as two separate reactions by different groups of bacteria
    • Ammonia oxidizers (e.g., Nitrosococcus)
    • Nitrite oxidizer (e.g., Nitrobacter)
  • Many species have internal membrane systems that house key enzymes in nitrification
  • Ammonia monooxygenase oxidizes NH3 to NH2OH
  • Nitrite oxidase oxidizes NO2- to NO3-

Planctomycetes

  • Some Planctomycetes have other internal membrane structures such as the annamoxosome and a nucleoid

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Fts proteins are essential for cell division in prokaryotes, forming the divisome. Min proteins regulate FtsZ ring formation. Prokaryotes also use cytoskeletal elements like crescentin and MreB to determine cell shape and morphology.

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